Publications for: James Biggs, David Frew, Ralph Martin, Andrew Williams
Perth Observatory staff names are in bold. The list is in descending time order.
Shortcut to non-refereed publications
Shortcut to last publication in each year: 2007, 2006, 2005, 2004, 2003, 2002, 2001, 2000, 1999, 1998, 1997, 1996, 1995, 1994, 1993, 1991, 1990
| Title: | MASH-II: more planetary nebulae from the AAO/UKST Ha survey | |
| Authors: | Miszalski, B.; Parker, Q. A.; Acker, A.; Birkby, J. L.; Frew, D. J. and Kovacevic, A. | |
| Journal: | Monthly Notices of the Royal Astronomical Society, 384, pp. 525-534. | |
| Publication Date: | 02/2008 | |
| Keywords: | astronomical data bases: miscellaneous, catalogues, surveys, planetary nebulae: general | |
| DOI: | 10.1111/j.1365-2966.2007.12727.x | |
| Abstract | ||
| We present a supplement to the Macquarie/AAO/Strasbourg Halpha planetary nebulae (PNe) catalogue (MASH), which we denote MASH-II. The supplement consists of over 300 true, likely and possible new Galactic PNe found after re-examination of the entire AAO/UKST Halpha survey of the Southern Galactic Plane in digital form. We have spectroscopically confirmed over 240 of these new candidates as bona fide PNe, and we include other high-quality candidates awaiting spectroscopic confirmation as possible PNe. These latest discoveries largely comprise two distinct groups: small, star like or moderately resolved PNe at one end and mostly large, extremely low surface brightness PNe at the other. Neither group were easy to discover from simple visual scrutiny of the original survey exposures as for MASH but were relatively straightforward to uncover from the digital images via application of semi-automated discovery techniques. We suspect the few PNe still hidden in the Ha survey will lie outside our search criteria or be difficult to find. | ||
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| Title: | Spitzer IRAC Observations of Newly Discovered Planetary Nebulae from the Macquarie-AAO-Strasbourg Ha Planetary Nebula Project | |
| Authors: | Cohen, M.; Parker, Q. A.; Green, A. J.; Murphy, T.; Miszalski, B.; Frew, D. J.; Meade, M. R.; Babler, B.; Indebetouw, R.; Whitney, B. A.; Watson, C.; Churchwell, E. B. and Watson, D. F. | |
| Journal: | The Astrophysical Journal, 669, pp. 343-362. | |
| Publication Date: | 11/2007 | |
| Keywords: | Infrared: ISM, ISM: Planetary Nebulae: General, Radiation Mechanisms: Thermal, Radio Continuum: ISM, Space Vehicles | |
| DOI: | 10.1086/521427 | |
| Abstract | ||
|
We compare Halpha, radio continuum, and Spitzer Space Telescope images of 58 planetary nebulae (PNe) recently discovered by the Macquarie-AAO-Strasbourg Halpha PN Project (MASH) of the SuperCOSMOS Halpha Survey. Using Infrared Array Camera (IRAC) data, we examine the relationships between optical and MIR morphologies from 3.6 to 8.0micron and explore the ratio of mid-infrared (MIR) to radio nebular fluxes, which is a valuable discriminant between thermal and nonthermal emission. MASH emphasizes late evolutionary stages of PNe compared with previous catalogs, enabling study of the changes in MIR and radio flux that attend the aging process. Spatially integrated fluxes are constructed for all MASH PNe observed by the GLIMPSE Legacy Project, using the Halpha morphologies to define the areas of MIR and radio continuum emission observed by the Midcourse Space Experiment (MSX), IRAC, the Molonglo Observatory Synthesis Telescope, and the Very Large Array (VLA). The ratio of IRAC 8.0micron to MSX 8.3micron fluxes provides an assessment of the absolute diffuse calibration of IRAC at 8.0micron. We independently confirm the aperture correction factor to be applied to IRAC at 8.0micron to align it with the diffuse calibration of MSX. The result is in accord with the recommendations of the Spitzer Science Center and with our results from a parallel study of HII regions in the MIR and radio. However, these PNe probe the diffuse calibration of IRAC on a spatial scale of 9''-77'', as opposed to the many-arcminute scale from the HII regions' study. | ||
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| Title: | Multiwavelength study of a new Galactic SNR G332.5-5.6 | |
| Authors: | Stupar, M.; Parker, Q. A.; Filipovic, M. D.; Frew, D. J.; Bojicic, I. and Aschenbach, B. | |
| Journal: | Monthly Notices of the Royal Astronomical Society, 381, pp. 377-388. | |
| Publication Date: | 10/2007 | |
| Keywords: | surveys, supernova remnants, radio continuum: general | |
| DOI: | 10.1111/j.1365-2966.2007.12296.x | |
| Abstract | ||
|
We present compelling evidence for confirmation of a Galactic supernova remnant (SNR) candidate, G332.5-5.6, based initially on identification of new, filamentary, optical emission-line nebulosity seen in the arcsecond resolution images from the Anglo Australian Observatory (AAO)/United Kingdom Schmidt Telescope (UKST) Halpha survey. The extant radio observations and X-ray data which we have independently re-reduced, together with new optical spectroscopy of the large-scale fragmented nebulosity, confirm the identification. Optical spectra, taken across five different, widely separated nebula regions of the remnant as seen in the Halpha images, show average ratios of [NII]/Halpha = 2.42, [SII]/Halpha = 2.10 and [SII] 6717/6731 = 1.23, as well as strong [OI] 6300, 6364 Å and [OII] 3727 Å emission. These ratios are firmly 3within those typical of SNRs. Here, we also present the radio-continuum detection of the SNR at 20/13cm from observations with the Australia Telescope Compact Array (ATCA). Radio emission is also seen at 4850 MHz, in the Parkes-MIT-NRAO (PMN) survey and at 843 MHz from the Sydney University Molonglo Sky Survey (SUMSS) survey. We estimate an angular diameter of ~30 arcmin and obtain an average radio spectral index of alpha = -0.6 ± 0.1 which indicates the non-thermal nature of G332.5-5.6. Fresh analysis of existing ROSAT X-ray data in the vicinity also confirms the existence of the SNR. The distance to G332.5-5.6 has been independently estimated by Reynoso and Green as 3.4 kpc based on measurements of the HI ?21-cm line seen in absorption against the continuum emission. Our cruder estimates via assumptions on the height of the dust layer (3.1 kpc) and using the Sigma-D relation (4 kpc) are in good agreement. | ||
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| Title: | On the Search for Transits of the Planets Orbiting Gliese 876 | |
| Authors: | Shankland, P. D.; Rivera, E. J.; Laughlin, G.; Blank, D. L.; Price, A.; Gary, B.; Bissinger, R.; Ringwald, F.; White, G.; Henry, G. W.; McGee, P.; Wolf, A. S.; Carter, B.; Lee, S.; Biggs, J.; Monard, B.; Ashley, M. C. B. | |
| Journal: | The Astrophysical Journal, 653, pp. 700-707. | |
| Publication Date: | 12/2006 | |
| Keywords: | Stars: Planetary Systems, Planets and Satellites: General, Stars: Individual: Name: Gliese 876 | |
| DOI: | 10.1086/508562 | |
| Abstract | ||
| We report the results of a globally coordinated photometric campaign to search for transits by the P~30 day and P~60 day outer planets of the three-planet system orbiting the nearby M dwarf Gl 876. These two planets experience strong mutual perturbations, which necessitate the use of a dynamical (four-body) model to compute transit ephemerides for the system. Our photometric data have been collected from published archival sources, as well as from our photometric campaigns that were targeted to specific transit predictions. Our analysis indicates that transits by planet c (P~30 days) do not currently occur, in concordance with the best-fit i=50° coplanar configuration obtained by dynamical fits to the most recent radial velocity data for the system. Transits by planet b (P~60 day) are not entirely ruled out by our observations, but our data indicate that it is very unlikely that they occur. Our experience with the Gl 876 system suggests that a distributed ground-based network of small telescopes can be used to search for transits of very low mass M stars by terrestrial-sized planets. | ||
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| Title: | OGLE 2004-BLG-254: a K3 III Galactic bulge giant spatially resolved by a single microlens | |
| Authors: | Cassan, A.; Beaulieu, J.-P.; Fouqué, P.; Brillant, S.; Dominik, M.; Greenhill, J.; Heyrovský, D.; Horne, K.; Jørgensen, U. G.; Kubas, D.; Stempels, H. C.; Vinter, C.; Albrow, M. D.; Bennett, D.; Caldwell, J. A. R.; Calitz, J. J.; Cook, K.; Coutures, C.; Dominis, D.; Donatowicz, J.; Hill, K.; Hoffman, M.; Kane, S.; Marquette, J.-B.; Martin, R.; Meintjes, P.; Menzies, J.; Miller, V. R.; Pollard, K. R.; Sahu, K. C.; Wambsganss, J.; Williams, A.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Soszynski, I.; Zebrun, K.; Szewczyk, O.; Wyrzykowski, L. | |
| Publication: | Astronomy and Astrophysics, Volume 460, Issue 1, December 2006, pp.277-288 | |
| Publication Date: | 12/2006 | |
| Keywords: | gravitational lensing, techniques: high angular resolution, stars: atmospheres, stars:, individual: OGLE 2004-BLG-254 | |
| DOI: | 10.1051/0004-6361:20054414 | |
| Abstract | ||
| Aims. We present an analysis
of OGLE 2004-BLG-254, a high-magnification (Ao ~
60) and relatively short duration (t_E ~ 13.2 days) microlensing event
in which the source star, a Bulge K-giant, has been spatially resolved
by a point-like lens. We seek to determine the lens and source distance,
and provide a measurement of the linear limb-darkening coefficients of
the source star in the I and R bands. We discuss the derived values of
the latter and compare them to the classical theoretical laws, and furthermore
examine the cases of already published microlensed GK-giants limb-darkening
measurements. Methods: We have obtained dense photometric coverage of the event light curve with OGLE and PLANET telescopes, as well as a high signal-to-noise ratio spectrum taken while the source was still magnified by A ~ 20, using the UVES/VLT spectrograph. We have performed a modelling of the light curve, including finite source and parallax effects, and have combined spectroscopic and photometric analysis to infer the source distance. A Galactic model for the mass and velocity distribution of the stars has been used to estimate the lens distance. Results: From the spectrum analysis and calibrated color-magnitude of the event target, we found that the source was a K3 III Bulge giant, situated at the far end of the Bulge. From modelling the light curve, we have derived an angular size of the Einstein ring theta_E ~ 114 muas, and a relative lens-source proper motion mu = theta_E/t_E ~ 3.1 mas/yr. We could also measure the angular size of the source, theta_* ~ 4.5 muas, whereas given the short duration of the event, no significant constraint could be obtained from parallax effects. A Galactic model based on the modelling of the light curve then provides us with an estimate of the lens distance, mass and velocity as D_L ~ 9.6 kpc, M ~ 0.11 Msun and v ~ 145~km s-1 (at the lens distance) respectively. Our dense coverage of this event allows us to measure limb darkening of the source star in the I and R bands. We also compare previous measurements of linear limb-darkening coefficients involving GK-giant stars with predictions from ATLAS atmosphere models. We discuss the case of K-giants and find a disagreement between limb-darkening measurements and model predictions, which may be caused by the inadequacy of the linear limb-darkening law. | ||
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| Title: | Piloting a network of small telescopes | |
| Authors: | Fadavi, M.; Verveer, A.; Aymon, J.; Merlin, D.; Situ, K.; Pennypackker, C.; Biggs, J. D.; White, G.; Gould, A.; Greenberg, G.; Hoette, V.; McCarron, K.; Archer, K.; Pino, F.; Hibbs, M.; Ford, M.; Wetsch, J. | |
| Journal: | Astronomische Nachrichten, Vol.327, Issue 8, p.811-813. | |
| Publication Date: | 09/2006 | |
| Keywords: | telescopes, methods: observational | |
| DOI: | 10.1002/asna.200610686 | |
| Abstract | ||
|
The Pilot Small Telescope Network (PSTN) is a state-of the art system of easily replicable and scalable hardware, software, servers, eXtensible Markup Language (XML) protocols, and network middleware connecting and developing a pilot array of robotic telescopes to one another and the user community. The PSTN is a developmental project that will allow growing access to these telescopes, and make available data to faculty, students and others in an environment of collaboration. The underlying goal of the PSTN is to broaden the quantity and quality of astronomical education and research, particularly with a focus on traditionally underserved populations. | ||
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| Title: | Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing | |
| Authors: | Beaulieu, J.-P.; Bennett, D. P.; Fouqué, P.; Williams, A.; Dominik, M.; Jorgensen, U. G.; Kubas, D.; Cassan, A.; Coutures, C.; Greenhill, J.; Hill, K.; Menzies, J.; Sackett, P. D.; Albrow, M.; Brillant, S.; Caldwell, J. A. R.; Calitz, J. J.; Cook, K. H.; Corrales, E.; Desort, M.; Dieters, S.; Dominis, D.; Donatowicz, J.; Hoffman, M.; Kane, S.; Marquette, J.-B.; Martin, R.; Meintjes, P.; Pollard, K.; Sahu, K.; Vinter, C.; Wambsganss, J.; Woller, K.; Horne, K.; Steele, I.; Bramich, D. M.; Burgdorf, M.; Snodgrass, C.; Bode, M.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Wieckowski, T.; Pietrzynski, G.; Soszynski, I.; Szewczyk, O.; Wyrzykowski, L.; Paczynski, B.; Abe, F.; Bond, I. A.; Britton, T. R.; Gilmore, A. C.; Hearnshaw, J. B.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Korpela, A. V.; Masuda, K.; Matsubara, Y.; Motomura, M.; Muraki, Y.; Nakamura, S.; Okada, C.; Ohnishi, K.; Rattenbury, N. J.; Sako, T.; Sato, S.; Sasaki, M.; Sekiguchi, T.; Sullivan, D. J.; Tristram, P. J.; Yock, P. C. M.; Yoshioka, T. | |
| Journal: | Nature, Volume 439, Issue 7075, pp. 437-440 (2006). | |
| Publication Date: | 01/2006 | |
| DOI: | 10.1038/nature04441 | |
| Abstract | ||
| In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive. Around M-dwarf stars (the most common stars in our Galaxy), this model favours the formation of Earth-mass (M⊕) to Neptune-mass planets with orbital radii of 1 to 10 astronomical units (AU), which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars. More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptune's mass or less have not hitherto been detected at separations of more than 0.15AU from normal stars. Here we report the discovery of a 5.5+5.5-2.7 M⊕ planetary companion at a separation of 2.6+1.5-0.6AU from a 0.22+0.21-0.11 M⊕ M-dwarf star, where M⊕ refers to a solar mass. (We propose to name it OGLE-2005-BLG-390Lb, indicating a planetary mass companion to the lens star of the microlensing event.) The mass is lower than that of GJ876d (ref. 5), although the error bars overlap. Our detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory. | ||
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| Title: | Full characterization of binary-lens event OGLE-2002-BLG-069 from PLANET observations | |
| Authors: | Kubas, D.; Beaulieu, J., P.; Coutures, C.; Dominik, M.; Albrow, M. D.; Brillant, S.; Caldwell, J. A. R.; Dominis, D.; Donatowicz, J.; Fendt, C.; Fouqué , P.; Jörgensen, U. G.; Greenhill, J.; Hill, K.; Heinmüller, J.; Horne, K.; Kane, S.; Marquette, J. B.; Martin, R.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Vinter, C.; Wambsganss, J.; Watson, R.; Williams, A.; Thurl, C. | |
| Journal: | Astronomy and Astrophysics, Volume 435, Issue 3, June I 2005, pp.941-948 | |
| Publication Date: | 06/2005 | |
| Keywords: | gravitational lensing, stars: atmospheres, stars: binaries: general | |
| DOI: | 10.1051/0004-6361:20042624 | |
| Abstract | ||
| We analyze the photometric data obtained by PLANET and OGLE on the caustic-crossing binary-lens microlensing event OGLE-2002-BLG-069. Thanks to the excellent photometric and spectroscopic coverage of the event, we are able to constrain the lens model up to the known ambiguity between close and wide binary lenses. The detection of annual parallax in combination with measurements of extended-source effects allows us to determine the mass, distance and velocity of the lens components for the competing models. While the model involving a close binary lens leads to a Bulge-Disc lens scenario with a lens mass of M=(0.51 ± 0.15) Msun; and distance of D{L}=(2.9± 0.4) {{kpc}}, the wide binary lens solution requires a rather implausible binary black-hole lens (M › 126 Msun). Furthermore we compare current state-of-the-art numerical and empirical models for the surface brightness profile of the source, a G5III Bulge giant. We find that a linear limb-darkening model for the atmosphere of the source star is consistent with the data whereas a PHOENIX atmosphere model assuming LTE and with no free parameter does not match our observations. | ||
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| Title: | Pushing the ground-based limit: 14-mumag photometric precision with the definitive Whole Earth Telescope asteroseismic data set for the rapidly oscillating Ap star HR1217 | |
| Authors: | Kurtz, D. W.; Cameron, C.; Cunha, M. S.; Dolez, N.; Vauclair, G.; Pallier, E.; Ulla, A.; Kepler, S. O.; da Costa, A.; Kanaan, A.; Fraga, L.; Giovannini, O.; Wood, M. A.; Silvestri, N.; Kawaler, S. D.; Riddle, R. L.; Reed, M. D.; Watson, T. K.; Metcalfe, T. S.; Mukadam, A.; Nather, R. E.; Winget, D. E.; Nitta, A.; Kleinman, S. J.; Guzik, J. A.; Bradley, P. A.; Matthews, J. M.; Sekiguchi, K.; Sullivan, D. J.; Sullivan, T.; Shobbrook, R.; Jiang, X.; Birch, P. V.; Ashoka, B. N.; Seetha, S.; Girish, V.; Joshi, S.; Moskalik, P.; Zola, S.; O'Donoghue, D.; Handler, G.; Mueller, M.; Perez Gonzalez, J. M. Solheim, J.-E.; Johannessen, F.; Bigot, L. | |
| Journal: | Monthly Notices of the Royal Astronomical Society, Volume 358, Issue 2, pp. 651-664. | |
| Publication Date: | 04/2005 | |
| Keywords: | stars: individual: HR1217, stars: magnetic fields, stars: oscillations, stars: variables: other | |
| DOI: | 10.1111/j.1365-2966.2005.08807.x | |
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| Title: | PLANET III: searching for Earth-mass planets via microlensing from Dome C? | |
| Authors: | Beaulieu, J. P.; Cassan, A.; Kubas, D.; Albrow, M.; Bennett, D.; Brillant, S.; Caldwell, J. A. R.; Calitz, H.; Cook, K.; Coutures, C.; Dominik, M.; Dominis, D.; Donatowicz, J.; Fouqué , P.; Greenhill, J.; Hill, K.; Hoffman, M.; Horne, K.; Jörgensen, U. G.; Kane, S.; Martin, R.; Mientjes, P.; Menzies, J. M.; Pollard, K.; Sahu, K.; Vinter, C.; Wambsganss, J.; Williams, A. | |
| Journal: | EAS Publications Series, Volume 14, 2005, pp.297-302 | |
| Publication Date: | 00/2005 | |
| DOI: | 10.1051/eas:2005047 | |
| Abstract | ||
|
PLANET, the Probing Lensing Anomaly NETwork, is an international team conducting observations of on-going gravitational microlensing events from five sites in the southern hemisphere. Our primary goal is to detect or to put constraints on sub-stellar companions of M dwarfs from the galactic disk. We report the current status and discuss the future prospects. A 2m robotic telescope at Dome C which would benefit from continuous coverage and dream like seeing (median of 0.27 arcsec) is currently the best option for a ground based aggressive search for Earth-mass planets in the habitable zone. | ||
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| Title: | OGLE-2003-BLG-238: Microlensing Mass Estimate of an Isolated Star | |
| Authors: | Jiang, Guangfei; DePoy, D. L.; Gal-Yam, A.; Gaudi, B. S.; Gould, A.; Han, C.; Lipkin, Y.; Maoz, D.; Ofek, E. O.; Park, B.-G.; Pogge, R. W.; Udalski, A.; Kubiak, M.; Szymanski, M. K.; Szewczyk, O.; Zebrun, K.; Wyrzykowski, L.; Soszynski, I.; Pietrzynski, G.; Albrow, M. D.; Beaulieu, J.-P.; Caldwell, J. A. R.; Cassan, A.; Coutures, C.; Dominik, M.; Donatowicz, J.; Fouqué , P.; Greenhill, J.; Hill, K.; Horne, K.; Jörgensen, S. F.; Jörgensen, U. G.; Kane, S.; Kubas, D.; Martin, R.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Wambsganss, J.; Watson, R.; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 617, Issue 2, pp. 1307-1315. | |
| Publication Date: | 12/2004 | |
| Keywords: | Cosmology: Gravitational Lensing, Stars: Fundamental Parameters | |
| DOI: | 10.1086/425678 | |
| Abstract | ||
| Microlensing is the only known direct method to measure the masses of stars that lack visible companions. In terms of microlensing observables, the mass is given by M=(c2/4G)rEthetaE and so requires the measurement of both the angular Einstein radius thetaE and the projected Einstein radius rE. Simultaneous measurement of these two parameters is extremely rare. Here we analyze OGLE-2003-BLG-238, a spectacularly bright (Imin=10.3), high-magnification (Amax=170) microlensing event. Pronounced finite-source effects permit a measurement of thetaE=650muas. Although the timescale of the event is only tE=38days, one can still obtain weak constraints on the microlens parallax: 4.4AU< rE< 18AU at the 1 sigma level. Together these two parameter measurements yield a range for the lens mass of 0.36Msolar< M< 1.48Msolar. As was the case for MACHO-LMC-5, the only other single star (apart from the Sun) whose mass has been determined from its gravitational effects, this estimate is rather crude. It does, however, demonstrate the viability of the technique. We also discuss future prospects for single-lens mass measurements. | ||
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| Title: | Potential Direct Single-Star Mass Measurement | |
| Authors: | Ghosh, H.; DePoy, D. L.; Gal-Yam, A.; Gaudi, B. S.; Gould, A.; Han, C.; Lipkin, Y.; Maoz, D.; Ofek, E. O.; Park, B.-G.; Pogge, R. W.; Salim, S.; Abe, F.; Bennett, D. P.; Bond, I. A.; Eguchi, S.; Furuta, Y.; Hearnshaw, J. B.; Kamiya, K.; Kilmartin, P. M.; Kurata, Y.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Noda, S.; Okajima, K.; Rattenbury, N. J.; Sako, T.; Sekiguchi, T.; Sullivan, D. J.; Sumi, T.; Tristram, P. J.; Yanagisawa, T.; Yock, P. C. M.; Udalski, A.; Soszynski, I.; Wyrzykowski, L.; Kubiak, M.; Szymanski, M. K.; Pietrzynski, G.; Szewczyk, O.; Zebrun, K.; Albrow, M. D.; Beaulieu, J.-P.; Caldwell, J. A. R.; Cassan, A.; Coutures, C.; Dominik, M.; Donatowicz, J.; Fouqué , P.; Greenhill, J.; Hill, K.; Horne, K.; Jörgensen, U. G.; Kane, S.; Kubas, D.; Martin, R.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Wambsganss, J.; Watson, R.; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 615, Issue 1, pp. 450-459. | |
| Publication Date: | 11/2004 | |
| Keywords: | Astrometry, Cosmology: Gravitational Lensing, Stars: Fundamental Parameters | |
| DOI: | 10.1086/423665 | |
| Abstract | ||
| We analyze the light curve of the microlensing event OGLE-2003-BLG-175/MOA-2003-BLG-45 and show that it has two properties that, when combined with future high-resolution astrometry, could lead to a direct, accurate measurement of the lens mass. First, the light curve shows clear signs of distortion due to the Earth's accelerated motion, which yields a measurement of the projected Einstein radius rE. Second, from precise astrometric measurements, we show that the blended light in the event is coincident with the microlensed source to within about 15 mas. This argues strongly that this blended light is the lens and hence opens the possibility of directly measuring the lens-source relative proper motion murel and so the mass M=(c2/4G)mureltErE, where tE is the measured Einstein timescale. While the light-curve-based measurement of rE is, by itself, severely degenerate, we show that this degeneracy can be completely resolved by measuring the direction of proper motion murel. | ||
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| Title: | Probing the atmosphere of the bulge G5III star OGLE-2002-BUL-069 by analysis of microlensed Halpha line | |
| Authors: | Cassan, A.; Beaulieu, J. P.; Brillant, S.; Coutures, C.; Dominik, M.; Donatowicz, J.; Jörgensen, U. G.; Kubas, D.; Albrow, M. D.; Caldwell, J. A. R.; Fouqué , P.; Greenhill, J.; Hill, K.; Horne, K.; Kane, S.; Martin, R.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Vinter, C.; Wambsganss, J.; Watson, R.; Williams, A.; Fendt, C.; Hauschildt, P.; Heinmueller, J.; Marquette, J. B.; Thurl, C. | |
| Journal: | Astronomy and Astrophysics, v.419, p.L1-L4 (2004) | |
| Publication Date: | 05/2004 | |
| Keywords: | techniques: gravitational microlensing, techniques: high resolution spectra, techniques: high angular resolution, stars: atmosphere models, stars: individual: OGLE 2002-BLG-069 | |
| DOI: | 10.1051/0004-6361:20040112 | |
| Abstract | ||
| We discuss high-resolution, time-resolved spectra of the caustic exit of the binary microlensing event OGLE 2002-BLG-069 obtained with UVES on the VLT. The source star is a G5III giant in the Galactic Bulge. During such events, the source star is highly magnified, and a strong differential magnification around the caustic resolves its surface. Using an appropriate model stellar atmosphere generated by the PHOENIX v2.6 code we obtain a model light curve for the caustic exit and compare it with a dense set of photometric observations obtained by the PLANET microlensing follow up network. We further compare predicted variations in the Halpha equivalent width with those measured from our spectra. While the model and observations agree in the gross features, there are discrepancies suggesting shortcomings in the model, particularly for the Halpha line core, where we have detected amplified emission from the stellar chromosphere after the source star's trailing limb exited the caustic. This achievement became possible by the provision of the very efficient OGLE-III Early Warning System, a network of small telescopes capable of nearly-continuous round-the-clock photometric monitoring, on-line data reduction, daily near-real-time modelling in order to predict caustic crossing parameters, and a fast and efficient response of a 8 m class telescope to a 'Target-of-Opportunity' observation request. | ||
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| Title: | High-Precision Limb-Darkening Measurement of a K3 Giant Using Microlensing | |
| Authors: | Fields, Dale L.; Albrow, M. D.; An, J.; Beaulieu, J.-P.; Caldwell, J. A. R.; DePoy, D. L.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Jörgensen, U. G.; Kane, S.; Martin, R.; Menzies, J.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A.; Glicenstein, J.-F.; Hauschildt, P. H. | |
| Journal: | The Astrophysical Journal, Volume 596, Issue 2, pp. 1305-1319. | |
| Publication Date: | 10/2003 | |
| Keywords: | Cosmology: Gravitational Lensing, Stars: Atmospheres | |
| Keywords: | gravitational lensing, stars: atmospheres, stars: | |
| DOI: | 10.1086/378196 | |
| Abstract | ||
| We obtain high-precision limb-darkening measurements in five bands (V, VE, IE, I, and H) for the K3 III (Teff=4200 K, [Fe/H]=+0.3, logg=2.3) source of the Galactic bulge microlensing event EROS BLG-2000-5. These measurements are inconsistent with the predictions of atmospheric models at higher than 10 sigma. While the disagreement is present in all bands, it is most apparent in I, IE, and VE, in part because the data are better and in part because the intrinsic disagreement is stronger. We find that when limb-darkening profiles are normalized to have unit total flux, the I-band models for a broad range of temperatures all cross each other at a common point. The solar profile also passes through this point. However, the profile as measured by microlensing does not. We hypothesize that the models have incorporated some aspect of solar physics that is not shared by giant atmospheres. | ||
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| Title: | Constraining the Evolution of ZZ Ceti | |
| Authors: | Mukadam, Anjum S.; Kepler, S. O.; Winget, D. E.; Nather, R. E.; Kilic, M.; Mullally, F.; von Hippel, T.; Kleinman, S. J.; Nitta, A.; Guzik, J. A.; Bradley, P. A.; Matthews, J.; Sekiguchi, K.; Sullivan, D. J.; Sullivan, T.; Shobbrook, R. R.; Birch, P.; Jiang, X. J.; Xu, D. W.; Joshi, S.; Ashoka, B. N.; Ibbetson, P.; Leibowitz, E.; Ofek, E. O.; Meistas, E. G.; Janulis, R.; Alisauskas, D.; Kalytis, R.; Handler, G.; Kilkenny, D.; O'Donoghue, D.; Kurtz, D. W.; Müller, M.; Moskalik, P.; Ogloza, W.; Zola, S.; Krzesinski, J.; Johannessen, F.; Gonzalez-Perez, J. M.; Solheim, J.-E.; Silvotti, R.; Bernabei, S.; Vauclair, G.; Dolez, N.; Fu, J. N.; Chevreton, M.; Manteiga, M.; Suárez, O.; Ulla, A.; Cunha, M. S.; Metcalfe, T. S.; Kanaan, A.; Fraga, L.; Costa, A. F. M.; Giovannini, O.; Fontaine, G.; Bergeron, P.; O'Brien, M. S.; Sanwal, D.; Wood, M. A.; Ahrens, T. J.; Silvestri, N.; Klumpe, E. W.; Kawaler, S. D.; Riddle, R.; Reed, M. D.; Watson, T. K. | |
| Journal: | The Astrophysical Journal, Volume 594, Issue 2, pp. 961-970. | |
| Publication Date: | 09/2003 | |
| Keywords | Stars: Evolution, stars: individual (ZZ Ceti, R548), Stars: Oscillations, Stars: Variables: Other, Stars: White Dwarfs | |
| DOI: | 10.1086/377044 | |
| ^ Top ^ |
| Title: | Amplitude and frequency variability of the pulsating DB white dwarf stars KUV 05134+2605 and PG 1654+160 observed with the Whole Earth Telescope | |
| Authors: | Handler, G.; O'Donoghue, D.; Müller, M.; Solheim, J.-E.; Gonzalez-Perez, J. M.; Johannessen, F.; Paparo, M.; Szeidl, B.; Viraghalmy, G.; Silvotti, R.; Vauclair, G.; Dolez, N.; Pallier, E.; Chevreton, M.; Kurtz, D. W.; Bromage, G. E.; Cunha, M. S.; Østensen, R.; Fraga, L.; Kanaan, A.; Amorim, A.; Giovannini, O.; Kepler, S. O.; da Costa, A. F. M.; Anderson, R. F.; Wood, M. A.; Silvestri, N.; Klumpe, E. W.; Carlton, R. F.; Miller, R. H.; McFarland, J. P.; Grauer, A. D.; Kawaler, S. D.; Riddle, R. L.; Reed, M. D.; Nather, R. E.; Winget, D. E.; Hill, J. A.; SMetcalfe, T. S.; Mukadam, A. S.; Kilic, M.; Watson, T. K.; Kleinman, S. J.; Nitta, A.; Guzik, J. A.; Bradley, P. A.; Sekiguchi, K.; Sullivan, D. J.; Sullivan, T.; Shobbrook, R. R.; Jiang, X.; Birch, P. V.; Ashoka, B. N.; Seetha, S.; Girish, V.; Joshi, S.; Dorokhova, T. N.; Dorokhov, N. I.; Akan, M. C.; Meistas, E. G.; Janulis, R.; Kalytis, R.; Alisauskas, D.; Anguma, S. K.; Kalebwe, P. C.; Moskalik, P.; Ogloza, W.; Stachowski, G.; Pajdosz, G.; Zola, S. | |
| Journal: | Monthly Notice of the Royal Astronomical Society, Volume 340, Issue 3, pp. 1031-1038. | |
| Publication Date: | 04/2003 | |
| Keywords: | stars: individual: KUV 05134+2605, stars: individual: PG 1654+160, stars: oscillations, stars: variables: other. | |
| DOI: | 10.1046/j.1365-8711.2003.06373.x | |
| ^ Top ^ |
| Title: | High Precision with the Whole Earth Telescope: Lessons and Some Results from XCov20 for the roAp Star HR 1217 | |
| Authors: | K Kurtz, D. W.; Kawaler, S. D.; Riddle, R. L.; Reed, M. D.; Cunha, M. S.; Wood, M.; Silvestri, N.; Watson, T. K.; Dolez, N.; Moskalik, P.; Zola, S.; Pallier, E.; Guzik, J. A.; Metcalfe, T. S.; Mukadam, A.; Nather, R. E.; Winget, D. E.; Sullivan, D. J.; Sullivan, T.; Sekiguchi, K.; Jiang, X. J.; Shobbrook, R. R.; Birch, P. V.; Ashoka, B. N.; Seetha, S.; Joshi, S.; Girish, V.; O'Donoghue, D.; Handler, G.; Mueller, M.; Gonzalez Perez, J. M.; Solheim, J.-E.; Johannessen, F.; Ulla, A.; Kepler, S. O.; Kanaan, A.; da Costa, A.; Fraga, L.; Giovannini, O.; Matthews, J. M.; Cameron, C.; Vauclair, G.; Nitta, A.; Kleinman, S. J. | |
| Journal: | Baltic Astronomy, v.12, p.105-117. | |
| Publication Date: | 00/2003 | |
| Keywords: | stars: roAp stars, stars: individual: HR 1217 | |
| ^ Top ^ |
| Title: | Constraining the Evolution of ZZ Ceti | |
| Authors: | Mukadam, A. S.; Kepler, S. O.; Winget, D. E.; Nather, R. E.; Kilic, M.; Mullally, F.; von Hippel, T.; Kleinman, S. J.; Nitta, A.; Guzik, J. A.; Bradley, P. A.; Matthews, J.; Sekiguchi, K.; Sullivan, D. J.; Sullivan, T.; Shobbrook, R. R.; Birch, P.; Jiang, X. J.; Xu, D. W.; Joshi, S.; Ashoka, B. N.; Ibbetson, P.; Leibowitz, E.; Ofek, E. O.; Meistas, E. G.; Janulis, R.; Alisauskas, D.; Kalytis, R.; Handler, G.; Kilkenny, D.; O O'Donoghue, D.; Kurtz, D. W.; Müller, M.; Moskalik, P.; Ogoza, W.; Zoa, S.; Krzesinski, J.; Johannessen, F.; Gonzalez-Perez, J. M.; Solheim, J.-E.; Silvotti, R.; Bernabei, S.; Vauclair, G.; Dolez, N.; Fu, J. N.; Chevreton, M.; Manteiga, M.; Suárez, O.; Ulla, A.; Cunha, M. S.; Metcalfe, T. S.; Kanaan, A.; Fraga, L.; Costa, A. F. M.; Giovannini, O.; Fontaine, G.; Bergeron, P.; O'Brien, M. S.; Sanwal, D.; Wood, M. A.; Ahrens, T. J.; Silvestri, N.; Klumpe, E. W.; Kawaler, S. D.; Riddle, R.; Reed, M. D.; Watson, T. K. | |
| Journal: | Baltic Astronomy, v.12, p.71-103. | |
| Publication Date: | 00/2003 | |
| Keywords: | stars: white dwarfs: individual: ZZ Cet, R 548, stars: pulsations, evolution | |
| ^ Top ^ |
| Title: | Optical Observations and Orbital Parameters of the Close DA plus dMe Binaries BPM 71214, EUVE J0720-31.7, BPM 6502, and EC 13471-1258 | |
| Authors: | Kawka, Adela; Vennes, Stéphane; Koch, Rolf; Williams, Andrew | |
| Journal: | The Astronomical Journal, Volume 124, Issue 5, pp. 2853-2867. | |
| Publication Date: | 11/2002 | |
| Keywords: | Stars: Binaries: Close, stars: individual (BPM 71214), stars: individual (EUVE J0720-31.7), Stars: Individual: Alphanumeric: BPM 6502, stars: individual (EC 13471-1258), Stars: White Dwarfs | |
| DOI: | 10.1086/343836 | |
| Abstract | ||
| We have obtained photometric and spectroscopic observations of the close DA plus dMe binaries BPM 6502 and EC 13471-1258, and spectroscopic observations of the close binaries BPM 71214 and EUVE J0720-31.7. We have updated the ephemerides of BPM 6502 and EUVE J0720-31.7 with the spectroscopic measurements and obtained periods of 0.20162 and 0.15074 days for BPM 71214 and EC 13471-1258, respectively, by measuring the shift in Halpha emission. Photometric variations in R and I due to reprocessing of incoming radiation from the hot white dwarf were observed in BPM 6502. We have also observed eclipses and ellipsoidal variations in B and R for EC 13471-1258, suggesting that the secondary is nearly filling its Roche lobe. | ||
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| Title: | A Short, Nonplanetary, Microlensing Anomaly: Observations and Light-Curve Analysis of MACHO 99-BLG-47 | |
| Authors: | Albrow, M. D.; An, J.; Beaulieu, J.-P.; Caldwell, J. A. R.; DePoy, D. L.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 572, Issue 2, pp. 1031-1040. | |
| Publication Date: | 06/2002 | |
| Keywords: | Stars: Binaries: General, Cosmology: Gravitational Lensing, Stars: Planetary Systems | |
| DOI: | 10.1086/340310 | |
| Abstract | ||
| We analyze PLANET and MACHO observations of MACHO 99-BLG-47, the first nearly normal microlensing event for which high signal-to-noise ratio data reveal a well-covered, short-duration anomaly. This anomaly occurs near the peak of the event. Short-duration anomalies near the peak of otherwise normal events are expected to arise both from extreme-separation (either very close or very wide), roughly equal-mass binary lenses and from planetary systems. We show that the lens of MACHO 99-BLG-47 is in fact an extreme-separation binary, not a planetary system, thus demonstrating for the first time that these two important classes of events can be distinguished in practice. However, we find that the wide-binary and close-binary lens solutions fit the data equally well and cannot be distinguished even at Deltachi2=1. This degeneracy is qualitatively much more severe than the one identified for MACHO 98-SMC-1 because the present degeneracy spans two rather than one dimension in the magnification field and does not require significantly different blending fractions. In the Appendix, we explore this result and show that it is related to the symmetry in the lens equation. | ||
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| Title: | First Microlens Mass Measurement: PLANET Photometry of EROS BLG-2000-5 | |
| Authors: | An, Jin H.; Albrow, M. D.; Beaulieu, J.-P.; Caldwell, J. A. R.; DePoy, D. L.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 572, Issue 1, pp. 521-539. | |
| Publication Date: | 06/2002 | |
| Keywords: | Stars: Binaries: General, Cosmology: Gravitational Lensing, Stars: Fundamental Parameters | |
| DOI: | 10.1086/340191 | |
| Abstract | ||
| We analyze PLANET photometric observations of the caustic-crossing binary lens microlensing event, EROS BLG-2000-5, and find that modeling the observed light curve requires incorporation of the microlens parallax and the binary orbital motion. The projected Einstein radius (rE=3.61±0.11 AU) is derived from the measurement of the microlens parallax, and we are also able to infer the angular Einstein radius (thetaE=1.38±0.12 mas) from the finite source effect on the light curve, combined with an estimate of the angular size of the source given by the source position in a color-magnitude diagram. The lens mass, M=0.612±0.057 Msolar, is found by combining these two quantities. This is the first time that parallax effects are detected for a caustic-crossing event and also the first time that the lens mass degeneracy has been completely broken through photometric monitoring alone. The combination of rE and thetaE also allows us to conclude that the lens lies in the near side of the disk, within 2.6 kpc of the Sun, while the radial velocity measurement indicates that the source is a Galactic bulge giant. | ||
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| Title: | Photometry and Imaging of Comet C/2000 WM1 (Linear) | |
| Authors: | Schleicher, David G.; Woodney, Laura M.; Birch, Peter V. | |
| Journal: | Earth, Moon, and Planets, v. 90, Issue 1, p. 401-403 (2002). | |
| Publication Date: | 03/2002 | |
| Keywords: | C/2000 WM1, C/LINEAR (2001 WM1), comet, imaging, narrowband photometry | |
| ^ Top ^ |
| Title: | Microlensing Constraints on the Frequency of Jupiter-Mass Companions: Analysis of 5 Years of PLANET Photometry | |
| Authors: | Gaudi, B. S.; Albrow, M. D.; An, J.; Beaulieu, J.-P.; Caldwell, J. A. R.; DePoy, D. L.; Dominik, M.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pel, J.-W.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Vreeswijk, P. M.; Watson, R.; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 566, Issue 1, pp. 463-499. | |
| Publication Date: | 02/2002 | |
| Keywords: | Cosmology: Gravitational Lensing, Stars: Planetary Systems, Stars: Low-Mass, Brown Dwarfs | |
| DOI: | 10.1086/337987 | |
| Abstract | ||
| We analyze 5 years of PLANET photometry of microlensing events toward the Galactic bulge to search for the short-duration deviations from single-lens light curves that are indicative of the presence of planetary companions to the primary microlenses. Using strict event-selection criteria, we construct a well-defined sample of 43 intensively monitored events. We search for planetary perturbations in these events over a densely sampled region of parameter space spanning two decades in mass ratio and projected separation, but find no viable planetary candidates. By combining the detection efficiencies of the events, we find that, at 95% confidence, less than 25% of our primary lenses have companions with mass ratio q=10-2 and separations in the lensing zone, [0.6-1.6]thetaE, where thetaE is the Einstein ring radius. Using a model of the mass, velocity, and spatial distribution of bulge lenses, we infer that the majority of our lenses are likely M dwarfs in the Galactic bulge. We conclude that less than 33% of M dwarfs in the Galactic bulge have companions with mass mp=MJ between 1.5 and 4 AU, and less than 45% have companions with mp=3MJ between 1 and 7 AU, the first significant limits on planetary companions to M dwarfs. We consider the effects of the finite size of the source stars and changing our detection criterion, but find that these do not alter our conclusions substantially. | ||
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| Title: | A Search for the Potentially Hazardous Asteroid 1998 OX4: Implications for a Possible Close Encounter in 2014 | |
| Authors: | Biggs, James D.; Slivkoff, Matthew | |
| Journal: | Publications of the Astronomical Society of Australia, Volume 19, Issue 4, pp. 422-424. | |
| Publication Date: | 00/2002 | |
| Keywords: | asteroids: impacts, orbit, 1998 OX4 | |
| DOI: | 10.1071/AS02002 | |
| Abstract | ||
| Small bodies of 100-500m diameter can cause significant damage on impact with the Earth. Such objects are difficult to detect and track because they are intrinsically faint over most of their orbit. We failed to detect one such lost and potentially hazardous minor planet, 1998 OX4, during two observing sessions in 2001, January. The positions searched were those calculated by Milani et al. (2000) with their Virtual Impactors method. Using some simple assumptions we estimate the probability that we failed to detect 1998 OX4 due to it being obscured by objects in the field of our observations is <2×10-7. If the assumptions in the Virtual Impactor model are valid we conclude that an impact with 1998 OX4 is unlikely in 2014, January. Furthermore, given the relatively large area we searched it is also unlikely that this minor planet will have a very close encounter with Earth in 2014. | ||
| Full text available - email J Biggs | ^ Top ^ |
| Title: | Limits on the Abundance of Galactic Planets From 5 Years of PLANET Observations | |
| Authors: | Albrow, M. D.; An, J.; Beaulieu, J.-P.; Caldwell, J. A. R.; DePoy, D. L.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pel, J.-W.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Vreeswijk, P. M.; Watson, R; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 556, Issue 2, pp. L113-L116. | |
| Publication Date: | 08/2001 | |
| Keywords: | Cosmology: Gravitational Lensing, Stars: Planetary Systems, Stars: Late-Type, Stars: Low-Mass, Brown Dwarfs, Techniques: Photometric | |
| DOI: | 10.1086/323141 | |
| Abstract | ||
| We search for signatures of planets in 43 intensively monitored microlensing events that were observed between 1995 and 1999. Planets would be expected to cause a short-duration (~1 day) deviation on the smooth, symmetric light curve produced by a single lens. We find no such anomalies and infer that less than one-third of the ~0.3 Msolar stars that typically comprise the lens population have Jupiter mass companions with semimajor axes in the range of 1.5 AU< a< 4 AU. Since orbital periods of planets at these radii are 3-15 yr, the outer portion of this region is currently difficult to probe with any other technique. | ||
| ^ Top ^ | ||
| Title: | Imaging and Photometry of Comet C/1999 S4 (LINEAR) Before Perihelion and After Breakup | |
| Authors: | Farnham, Tony L.; Schleicher, David G.; Woodney, Laura M.; Birch, Peter V.; Eberhardy, Clara A.; Levy, Lorenza | |
| Journal: | Science, Volume 292, Issue 5520, pp. 1348-1354 (2001). | |
| Publication Date: | 05/2001 | |
| DOI: | 10.1126/science.1058886 | |
| ^ Top ^ |
| Title: | Halpha Equivalent Width Variations across the Face of a Microlensed K Giant in the Galactic Bulge | |
| Authors: | Albrow, M.; An, J.; Beaulieu, J.-P.; Caldwell, J. A. R.; Dominik, M.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Pollard, K.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A.; Hauschildt, P. H. | |
| Journal: | The Astrophysical Journal, Volume 550, Issue 2, pp. L173-L177. | |
| Publication Date: | 04/2001 | |
| Keywords: | Cosmology: Gravitational Lensing, Stars: Atmospheres, Stars: Fundamental Parameters, stars: individual (EROS 2000-BLG-5) | |
| DOI: | 10.1086/319635 | |
| Abstract | ||
| We present Very Large Telescope FORS1 spectroscopy that temporally resolves the second caustic crossing of the Galactic bulge K giant source of microlensing event EROS 2000-BLG-5, the first time this has been accomplished for several phases of a caustic transit. The ~1 Å Halpha equivalent width of the source star increases slightly as the center of the star egresses the caustic and then plummets by 30% during the final limb crossing. These changes are not seen in contemporaneous spectra of control stars in the FORS1 slit but are qualitatively consistent with expectations from stellar atmosphere models as the caustic differentially magnifies different portions of the stellar face of the target. Observations such as these in a variety of stellar lines are equivalent to atmospheric tomography and are expected to provide a direct test of stellar models. | ||
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| Title: | PLANET Observations of Microlensing Event OGLE-1999-BUL-23: Limb-darkening Measurement of the Source Star | |
| Authors: | Albrow, M. D.; An, J.; Beaulieu, J.-P.; Caldwell, J. A. R.; DePoy, D. L.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 549, Issue 2, pp. 759-769. | |
| Publication Date: | 03/2001 | |
| Keywords: | Stars: Binaries: General, Cosmology: Gravitational Lensing, Stars: Atmospheres, Stars: Fundamental Parameters | |
| DOI: | 10.1086/319437 | |
| Abstract | ||
| We present PLANET observations of OGLE-1999-BUL-23, a binary-lens microlensing event toward the Galactic bulge. PLANET observations in the I and V bands cover the event from just before the first caustic crossing until the end of the event. In particular, a densely sampled second caustic crossing enables us to derive the linear limb-darkening coefficients of the source star: cV=0.786+0.080-0.078 and cI=0.632+0.047-0.037. Combined analysis of the light curve and the color-magnitude diagram suggests that the source star is a G/K subgiant in the Galactic bulge (Teff~=4800 K). The resulting linear limb-darkening coefficient of the source is consistent with theoretical predictions, although it is likely that nonlinearity of the stellar surface brightness profile complicates the interpretation, especially for the I band. The global light curve fit to the data indicates that the event is due to a binary lens of a mass ratio q~=0.39 and a projected separation d~=2.42. The lens/source relative proper motion is (22.8±1.5) km s-1 kpc-1, typical of bulge/bulge or bulge/disk events. | ||
| ^ Top ^ | ||
| Title: | Delta Scuti Network observations of XX Pyx: detection of 22 pulsation modes and of short-term amplitude and frequency variations | |
| Authors: | Handler, G.; Arentoft, T.; Shobbrook, R. R.; Wood, M. A.; Crause, L. A.; Crake, P.; Podmore, F.; Habanyama, A.; Oswalt, T.; Birch, P. V.; Lowe, G.; Sterken, C.; Meintjes, P.; Brink, J.; Claver, C. F.; Medupe, R.; Guzik, J. A.; Beach, T. E.; Martinez, P.; Leibowitz, E. M.; Ibbetson, P. A.; Smith, T.; Ashoka, B. N.; Raj, N. E.; Kurtz, D. W.; Balona, L. A.; O'Donoghue, D.; Costa, J. E. S.; Breger, M. | |
| Journal: | Monthly Notices of the Royal Astronomical Society, Volume 318, Issue 2, pp. 511-525. | |
| Publication Date: | 10/2000 | |
| Keywords: | TECHNIQUES: PHOTOMETRIC, STARS: INDIVIDUAL: CD-24 7599, STARS: INDIVIDUAL: XX PYX, STARS: OSCILLATIONS, &DELTA; SCUTI | |
| ^ Top ^ |
| Title: | Discovery of the Optical Counterpart and Early Optical Observations of GRB 990712 | |
| Authors: | Sahu, K. C.; Vreeswijk, P.; Bakos, G.; Menzies, J. W.; Bragaglia, A.; Frontera, F.; Piro, L.; Albrow, M. D.; Bond, I. A.; Bower, R.; Caldwell, J. A. R.; Castro-Tirado, A. J.; Courbin, F.; Dominik, M.; Fynbo, J. U.; Galama, T.; Glazebrook, K.; Greenhill, J.; Gorosabel, J.; Hearnshaw, J.; Hill, K.; Hjorth, J.; Kane, S.; Kilmartin, P. M.; Kouveliotou, C.; Martin, R.; Masetti, N.; Maxted, P.; Minniti, D.; Müller, P.; Muraki, Y.; Nakamura, T.; Noda, S.; Ohnishi, K.; Palazzi, E.; van Paradijs, J.; Pian, E.; Pollard, K. R.; Rattenbury, N. J.; Reid, M.; Rol, E.; Saito, T.; Sackett, P. D.; Saizar, P.; Tinney, C.; Vermaak, P.; Watson, R.; Williams, A.; Yock, P.; Dar, A. | |
| Journal: | The Astrophysical Journal, Volume 540, Issue 1, pp. 74-80. | |
| Publication Date: | 09/2000 | |
| Keywords: | Cosmology: Observations, Gamma Rays: Bursts | |
| DOI: | 10.1086/309340 | |
| Abstract | ||
| We present the discovery observations of the optical counterpart of the gamma-ray burst GRB 990712 taken 4.16 hr after the outburst and discuss its light curve observed in the V, R, and I bands during the first ~35 days after the outburst. The observed light curves were fitted with a power-law decay for the optical transient (OT), plus an additional component that was treated in two different ways. First, the additional component was assumed to be an underlying galaxy of constant brightness. The resulting slope of the decay is 0.97+0.05-0.02, and the magnitudes of the underlying galaxy are V=22.3±0.05, R=21.75±0.05, and I=21.35±0.05. Second, the additional component was assumed to be a galaxy plus an underlying supernova with a time-variable brightness identical to that of GRB 980425, appropriately scaled to the redshift of GRB 990712. The resulting slope of the decay is similar, but the goodness of fit is worse, which would imply that either this GRB is not associated with an underlying supernova or the underlying supernova is much fainter than the supernova associated with GRB 980425. The galaxy in this case is fainter: V=22.7±0.05, R=22.25±0.05, and I=22.15±0.05, and the OT plus the underlying supernova at a given time is brighter. Measurements of the brightnesses of the OT and the galaxy by late-time Hubble Space Telescope observation and ground-based observations can thus assess the presence of an underlying supernova. Based on observations collected at SAAO, Sutherland; ESO, Paranal and La Silla (ESO Programs 63.O-0618 and 63-O-0567) and AAT, Australia. | ||
| ^ Top ^ | ||
| Title: | Limits on Stellar and Planetary Companions in Microlensing Event OGLE-1998-BUL-14 | |
| Authors: | Gaudi, B. S.; Beaulieu, J.-P.; Caldwell, J. A. R.; DePoy, D. L.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 535, Issue 1, pp. 176-189. | |
| Publication Date: | 05/2000 | |
| Keywords: | Cosmology: Dark Matter, Cosmology: Gravitational Lensing, Stars: Planetary Systems | |
| DOI: | 10.1086/308842 | |
| Abstract | ||
| We present the PLANET photometric data set for OGLE-1998-BUL-14, a high-magnification (Amax~16) event alerted by the OGLE collaboration toward the Galactic bulge in 1998. The PLANET data set consists a total of 461 I-band and 139 V-band points, the majority of which was taken over a 3 month period. The median sampling interval during this period is about 1 hr, and the 1 sigma scatter over the peak of the event is 1.5%. The excellent data quality and high maximum magnification of this event make it a prime candidate to search for the short-duration, low-amplitude perturbations that are signatures of a planetary companion orbiting the primary lens. The observed light curve for OGLE-1998-BUL-14 is consistent with a single lens (no companion) within photometric uncertainties. We calculate the detection efficiency of the light curve to lensing companions as a function of the mass ratio and angular separation of the two components. We find that companions of mass ratio > =0.01 are ruled out at the 95% significance level for projected separations between 0.4 and 2.4rE, where rE is the Einstein ring radius of the primary lens. Assuming that the primary is a G dwarf with rE~3 AU, our detection efficiency for this event is ~60% for a companion with the mass and separation of Jupiter and ~5% for a companion with the mass and separation of Saturn. Our efficiencies for planets like those around upsilo And and 14 Her are > 75%. | ||
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| Title: | Detection of Rotation in a Binary Microlens: PLANET Photometry of MACHO 97-BLG-41 | |
| Authors: | Albrow, M. D.; Beaulieu, J.-P.; Caldwell, J. A. R.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A.; Bond, H. E.; van Bemmel, I. M. | |
| Journal: | The Astrophysical Journal, Volume 534, Issue 2, pp. 894-906. | |
| Publication Date: | 05/2000 | |
| Keywords: | Stars: Binaries: General, Cosmology: Gravitational Lensing, Stars: Planetary Systems | |
| DOI: | 10.1086/308798 | |
| Abstract | ||
| We analyze PLANET collaboration data for MACHO 97-BLG-41, the only microlensing event observed to date in which the source transits two disjoint caustics. The PLANET data, consisting of 46 V-band and 325 I-band observations from five southern observatories, span a period from the initial alert until the end of the event. Our data are incompatible with a static binary lens, but are well fitted by a rotating binary lens of mass ratio q=0.34 and angular separation d~0.5 (in units of the Einstein ring radius), in which the binary separation changes in size by deltad=-0.070±0.009 and in orientation by deltatheta=5.61d±0.36d during the 35.17 days between the separate caustic transits. We use this measurement, combined with other observational constraints, to derive the first kinematic estimate of the mass, distance, and period of a binary microlens. The relative probability distributions for these parameters peak at a total lens mass M~0.3 Msolar (M-dwarf binary system), lens distance DL~5.5 kpc, and binary period P~1.5 yr. The robustness of our model is demonstrated by its striking agreement with MACHO/GMAN data that cover several sharp features in the light curve not probed by the PLANET observations, and which did not enter our modeling procedure in any way. Available data sets thus indicate that the light curve of MACHO 97-BLG-41 can be modeled as a source crossing two caustics of a physically realistic rotating binary. Thus, contrary to a recent suggestion, the additional effects of a postulated planetary companion to the binary lens are not required. Based on observations at Canopus Observatory, Tasmania, Australia; Perth Observatory, Bickley, Australia; the South African Astronomical Observatory, Sutherland, South Africa; the European Southern Observatory, La Silla, Chile; and the Cerro Tololo Inter-American Observatory, Cerro Tololo, Chile. | ||
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| Title: | Combined Analysis of the Binary Lens Caustic-crossing Event MACHO 98-SMC-1 | |
| Authors: | fonso, C; ; Alard, C.; Albert, J. N.; Andersen, J.; Ansari, R.; Aubourg, É Bareyre, P.; Bauer, F.; Beaulieu, J. P.; Bouquet, A.; Char, S.; Charlot, X.; Couchot, F.; Coutures, C.; Derue, F.; Ferlet, R.; Glicenstein, J. F.; Goldman, B.; Gould, A.; Graff, D.; Gros, M.; Haissinski, J.; Hamilton, J. C.; Hardin, D.; de Kat, J.; Kim, A.; Lasserre, T.; Lesquoy, É .; Loup, C.; Magneville, C.; Marquette, J. B.; Maurice, É Milsztajn, A.; Moniez, M.; Palanque-Delabrouille, N.; Perdereau, O.; Pré vot, L.; Regnault, N.; Rich, J.; Spiro, M.; Vidal-Madjar, A.; Vigroux, L.; Zylberajch, S.; Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Becker, A. C.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.; King, L. J.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Peterson, B. A.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Stetson, P. B.; Stubbs, C. W.; Sutherland, W.; Tomaney, A.; Vandehei, T.; Rhie, S. H.; Bennett, D. P.; Fragile, P. C.; Johnson, B. R.; Quinn, J.; Udalski, A.; Kubiak, M.; Szymanski, M.; Pietrzynski, G.; Wozniak, P.; Zebrun, K.; Albrow, M. D.; Caldwell, J. A. R.; DePoy, D. L.; Dominik, M.; Gaudi, B. S.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A. | |
| Journal: | The Astrophysical Journal, Volume 532, Issue 1, pp. 340-352. | |
| Publication Date: | 03/2000 | |
| Keywords: | ASTROMETRY, COSMOLOGY: DARK MATTER, COSMOLOGY: GRAVITATIONAL LENSING, GALAXIES: MAGELLANIC CLOUDS | |
| DOI: | 10.1086/308561 | |
| Abstract | ||
| We fit the data for the binary lens microlensing event MACHO 98-SMC-1 from five different microlensing collaborations and find two distinct solutions characterized by binary separation d and mass ratio q: (d,q)=(0.54,0.50) and (d,q)=(3.65,0.36), where d is in units of the Einstein radius. However, the relative proper motion of the lens is very similar in the two solutions, 1.30 km s-1 kpc-1 and 1.48 km s-1 kpc-1, thus confirming that the lens is in the Small Magellanic Cloud. The close binary can be either rotating or approximately static but the wide binary must be rotating at close to its maximum allowed rate to be consistent with all the data. We measure limb-darkening coefficients for five bands ranging from I to V. As expected, these progressively decrease with rising wavelength. This is the first measurement of limb darkening for a metal-poor A star. | ||
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| Title: | Time-series photometry of the delta Scuti star XX Pyx. A. Introduction and Overview | |
| Authors: | Handler, G.; Arentoft, T.; Shobbrook, R. R.; Sullivan, D. J.; Kleinman, S. J.; Clemens, J. C.; O'Donoghue, D.; Wood, M. A.; Crake, P.; Buckley, D. A. H.; Zima, W.; Kanaan, A.; Crause, L. A.; van der Peet, A. J.; Podmore, F.; Habanyama, A.; Oswalt, T.; Lowe, G.; Claver, C. F.; Chen, A.-L.; Birch, P. V.; Sterken, C.; Meintjes, P.; Brink, J.; Medupe, R.; Guzik, J. A.; Beach, T. E.; Martinez, P.; Audard, N.; Leibowitz, E. M.; Ibbetson, P. A.; Krisciunas, K.; Nitta, A.; Smith, T.; Giovannini, O.; Raj, N. E.; Ashoka, B. N.; Kurtz, D. W.; Watson, T. K.; O'Brien, M. S. | |
| Journal: | The Journal of Astronomical Data (JAD), Volume 6, Number 4A, 2000. | |
| Publication Date: | 00/2000 | |
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| Title: | Time-series photometry of the delta Scuti star XX Pyx F. Photoelectric observations from the Perth and Vainu Bappu Observatories | |
| Authors: | Birch, P.; Crake, P.; Lowe, G.; Smith, T.; Ashoka, B.; Raj, N.; Handler, G. | |
| Journal: | The Journal of Astronomical Data (JAD), Volume 6, Number 4F, 2000. | |
| Publication Date: | 00/2000 | |
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| Title: | A Complete Set of Solutions for Caustic Crossing Binary Microlensing Events | |
| Authors: | Albrow, M. D.; Beaulieu, J.-P.; Caldwell, J. A. R.; Depoy, D. L.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pogge, R. W.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A.; | |
| Journal: | The Astrophysical Journal, Volume 522, Issue 2, pp. 1022-1036. | |
| Publication Date: | 09/1999 | |
| Keywords: | ASTROMETRY, COSMOLOGY: DARK MATTER, COSMOLOGY: GRAVITATIONAL LENSING | |
| DOI: | 10.1086/307699 | |
| Abstract | ||
| We present a method to analyze binary lens microlensing light curves with one well-sampled fold caustic crossing. In general, the surface of chi^2 shows extremely complicated behavior over the nine-parameter space that characterizes binary lenses. This makes it difficult to systematically search the space and verify that a given local minimum is a global minimum. We show that for events with well-monitored caustics, the caustic crossing region can be isolated from the rest of the light curve and easily fitted to a five-parameter function. Four of these caustic crossing parameters can then be used to constrain the search in the larger nine-parameter space. This allows a systematic search for all solutions and thus identification of all local minima. We illustrate this technique using the PLANET data for MACHO 98-SMC-1, an excellent and publicly available caustic crossing data set. We show that a very broad range of parameter combinations are compatible with the PLANET data set, demonstrating that observations of binary lens light curves with a sampling of only one caustic crossing do not yield unique solutions. The corollary to this is that the time of the second caustic crossing cannot be reliably predicted on the basis of early data including the first caustic crossing alone. We investigate the requirements for determination of a unique solution and find that occasional observations of the first caustic crossing may be sufficient to derive a complete solution. | ||
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| Title: | Limb Darkening of a K Giant in the Galactic Bulge: PLANET Photometry of MACHO 97-BLG-28 | |
| Authors: | Albrow, M. D.; Beaulieu, J.-P.; Caldwell, J. A. R.; Dominik, M.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pel, J.-W.; Pollard, K.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A.; Sahu, M. S. | |
| Journal: | The Astrophysical Journal, Volume 522, Issue 2, pp. 1011-1021. | |
| Publication Date: | 09/1999 | |
| Keywords: | STARS: BINARIES: VISUAL, COSMOLOGY: GRAVITATIONAL LENSING, STARS: FUNDAMENTAL PARAMETERS, STARS: LATE-TYPE | |
| DOI: | 10.1086/307681 | |
| Abstract | ||
| We present the PLANET photometric data set for the binary-lens microlensing event MACHO 97-BLG-28, consisting of 696 I- and V-band measurements, and analyze it to determine the radial surface brightness profile of the Galactic bulge source star. The microlensed source, demonstrated to be a K giant by our independent spectroscopy, crossed an isolated cusp of the central caustic of the lensing binary, generating a sharp peak in the light curve that was well-resolved by dense (3-30 minute) and continuous monitoring from PLANET sites in Chile, South Africa, and Australia. This is the first time that such a cusp crossing has been observed. Analysis of the PLANET data set has produced a measurement of the square-root limb-darkening coefficients of the source star in the I and V bands; the resulting stellar profiles are in excellent agreement with those predicted by stellar atmospheric models for K giants. The limb-darkening coefficients presented here are the first derived from microlensing. They are also among the first found for normal giants by any technique and the first for any star as distant as the Galactic bulge. Modeling of our light curve for MACHO 97-BLG-28 indicates that the lensing binary has a mass ratio q=0.23 and an (instantaneous) separation in units of the angular Einstein ring radius of d=0.69. For a lens in the Galactic bulge, this corresponds to a typical stellar binary with a projected separation between 1 and 2 AU. If the lens lies closer (i.e., in the Galactic disk), the separation is smaller, and one or both of the lens objects is in the brown dwarf regime. Assuming that the source is a bulge K2 giant at 8 kpc, the relative lens-source proper motion is mu=19.4±2.6 km s^-1 kpc^-1, consistent with a disk or bulge lens. If the nonlensed blended light is due to a single star, it is likely to be a young white dwarf in the bulge, consistent with the blended light coming from the lens itself. | ||
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| Title: | Limb Darkening of a K Giant in the Galactic Bulge: PLANET Photometry of MACHO 97-BLG-28 | |
| Authors: | Albrow, M. D.; Beaulieu, J.-P.; Caldwell, J. A. R.; Dominik, M.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pel, J.-W.; Pollard, K.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A.; Sahu, M. S. | |
| Journal: | The Astrophysical Journal, Volume 522, Issue 2, pp. 1011-1021. | |
| Publication Date: | 09/1999 | |
| Keywords: | STARS: BINARIES: VISUAL, COSMOLOGY: GRAVITATIONAL LENSING, STARS: FUNDAMENTAL PARAMETERS, STARS: LATE-TYPE | |
| DOI: | 10.1086/307681 | |
| Abstract | ||
| We present the PLANET photometric data set for the binary-lens microlensing event MACHO 97-BLG-28, consisting of 696 I- and V-band measurements, and analyze it to determine the radial surface brightness profile of the Galactic bulge source star. The microlensed source, demonstrated to be a K giant by our independent spectroscopy, crossed an isolated cusp of the central caustic of the lensing binary, generating a sharp peak in the light curve that was well-resolved by dense (3-30 minute) and continuous monitoring from PLANET sites in Chile, South Africa, and Australia. This is the first time that such a cusp crossing has been observed. Analysis of the PLANET data set has produced a measurement of the square-root limb-darkening coefficients of the source star in the I and V bands; the resulting stellar profiles are in excellent agreement with those predicted by stellar atmospheric models for K giants. The limb-darkening coefficients presented here are the first derived from microlensing. They are also among the first found for normal giants by any technique and the first for any star as distant as the Galactic bulge. Modeling of our light curve for MACHO 97-BLG-28 indicates that the lensing binary has a mass ratio q=0.23 and an (instantaneous) separation in units of the angular Einstein ring radius of d=0.69. For a lens in the Galactic bulge, this corresponds to a typical stellar binary with a projected separation between 1 and 2 AU. If the lens lies closer (i.e., in the Galactic disk), the separation is smaller, and one or both of the lens objects is in the brown dwarf regime. Assuming that the source is a bulge K2 giant at 8 kpc, the relative lens-source proper motion is mu=19.4±2.6 km s^-1 kpc^-1, consistent with a disk or bulge lens. If the nonlensed blended light is due to a single star, it is likely to be a young white dwarf in the bulge, consistent with the blended light coming from the lens itself. | ||
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| Title: | The Relative Lens-Source Proper Motion in MACHO 98-SMC-1 | |
| Authors: | Albrow, M. D.; Beaulieu, J.-P.; Caldwell, J. A. R.; Depoy, D. L.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pollard, K. R.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A.; Pogge, R. W. | |
| Journal: | The Astrophysical Journal, Volume 512, Issue 2, pp. 672-677. | |
| Publication Date: | 02/1999 | |
| Keywords: | STARS: BINARIES: VISUAL, GALAXY: HALO, COSMOLOGY: GRAVITATIONAL LENSING, GALAXIES: MAGELLANIC CLOUDS | |
| DOI: | 10.1086/306820 | |
| Abstract | ||
| We present photometric and spectroscopic data for the second microlensing event seen toward the Small Magellanic Cloud (SMC), MACHO 98-SMC-1. The lens is a binary. We resolve the caustic crossing and find that the source took 2Deltat=8.5 hr to transit the caustic. We measure the source temperature T_eff=8000 K both spectroscopically and from the color, (V-I)_0~0.22. We find two acceptable binary-lens models. In the first, the source crosses the caustic at phi=43.2d and the unmagnified source magnitude is I_s=22.15. The angle implies that the lens crosses the source radius in time t_*=Deltatsinphi=2.92 hr. The magnitude (together with the temperature) implies that the angular radius of the source is theta_*=0.089 muas. Hence, the proper motion is mu=theta_*/t_*=1.26 km s^-1 kpc^-1. For the second solution, the corresponding parameters are phi=30.6d, I_s=21.81, t_*=2.15 hr, theta_*=0.104 muas, and mu=theta_*/t_*=2.00 km s^-1 kpc^-1. Both proper-motion estimates are slower than 99.5% of the proper motions expected for halo lenses. Both are consistent with an ordinary binary lens moving at ~75-120 km s^-1 within the SMC itself. We conclude that the lens is most likely in the SMC proper. | ||
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| Title: | The 1995 Pilot Campaign of PLANET: Searching for Microlensing Anomalies through Precise, Rapid, Round-the-Clock Monitoring | |
| Authors: | Albrow, M.; Beaulieu, J.-P.; Birch, P.; Caldwell, J. A. R.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pel, J.-W.; Pollard, K.; Sackett, P. D.; Sahu, K. C.; > Vreeswijk, P.; Williams, A.; Zwaan, M. A.; | |
| Journal: | The Astrophysical Journal, Volume 509, Issue 2, pp. 687-702. | |
| Publication Date: | 12/1998 | |
| Keywords: | GALAXY: STELLAR CONTENT, COSMOLOGY: GRAVITATIONAL LENSING, STARS: PLANETARY SYSTEMS, STARS: VARIABLES: OTHER, SURVEYS | |
| DOI: | 10.1086/306513 | |
| Abstract | ||
| PLANET (the Probing Lensing Anomalies NETwork) is a worldwide collaboration of astronomers whose primary goal is to monitor microlensing events densely and precisely in order to detect and study anomalies that contain information about Galactic lenses and sources that would otherwise be unobtainable. The results of PLANET's highly successful first year of operation are presented here. Details of the observational setup, observing procedures, and data-reduction procedures used to track the progress in real time at the three participating observing sites in 1995 are discussed. The ability to follow several events simultaneously with a median sampling interval of 1.6 hr and a photometric precision of better than 0.10 mag even at I = 19 has been clearly demonstrated. During PLANET's 1995 pilot campaign, ten microlensing events were monitored, resulting in the most precise and densely-sampled light curves to date; the binary nature of one of these, MACHO 95-BLG-12, was recognized by PLANET on the mountain. Another event, OGLE 95-BLG-04, displayed chromaticity that may betray the presence of blending with unresolved stars projected onto the same resolution element. Although lasting only about a month, the campaign may allow constraints to be placed on the number of planets with mass ratios to the parent star of 0.01 or greater. | ||
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| Title: | The 1998 PLANET Gravitational Microlensing Season | |
| Authors: | Depoy, D. L.; Albrow, M. D.; Beaulieu, J. P.; Caldwell, J.; Dominik, M.; Gaudi, B. S.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pel, J.-W.; Pogge, R.; Pollard, K.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A. | |
| Journal: | American Astronomical Society, 193rd AAS Meeting, #117.01; Bulletin of the American Astronomical Society, Vol. 30, p.1424 | |
| Publication Date: | 12/1998 | |
| Abstract | ||
| The Probing Lensing Anomalies NETwork is an international collaboration that makes coordinated observations of on-going graviational microlensing events from four sites in the southern hemisphere. One of our primary goals is to detect planets around other stars from their microlensing effect. During the 1998 bulge observing season we intensely monitored numerous microlensing events; one event was observed more than 500 times at I and 200 times at V. The frequency and general quality of our photometry gives us excellent sensitivity to second order gravitational microlensing effects (such as those due to the presence of a planet). | ||
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| Title: | Limits on Planetary Companions in Microlensing Event OGLE-BUL-98-14 | |
| Authors: | Gaudi, B. S.; Albrow, M. D.; Beaulieu, J. P.; Caldwell, J. A. R.; Depoy, D. L.; Dominik, M.; Gould, A.; Greenhill, J.; Hill, K.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pogge, R. W.; Pollard, K.; Sackett, P. D.; Sahu, K. C.; Vermaak, P.; Watson, R.; Williams, A. | |
| Journal: | American Astronomical Society, 193rd AAS Meeting, #108.07; Bulletin of the American Astronomical Society, Vol. 30, p.1416 | |
| Publication Date: | 12/1998 | |
| Abstract | ||
| As part of an ongoing effort to detect second order effects in gravitational microlensing events, the Probing Lensing Anomalies NETwork (PLANET) collaboration has obtained nearly continuous photometry of the microlensing event OGLE-BUL-98-14 with four telescopes located in Tasmania, Perth, South Africa and Chile. The complete data set consists of over 500 points in I and 200 in V taken over a period of ~ 120 days, making this one of the most well sampled microlensing events to date. The scatter in I is ~ 2% (1 sigma). OGLE-BUL-98-14 was a high magnification event (maximum magnification > 10) with a timescale of ~ 40 days. These facts, combined with the high sampling rate and good photometry, make this an extremely promising event for detection of second order effects. We find that the observed lightcurve is completely consistent with a point-source point-lens model. We can rule out the presence of a companion with mass ratio > 10(-3) over a substantial range of projected separations. Furthermore, the lack of detected finite-source or parallax effects allows us to put a lower limit on the mass of the lens, Mlens > 0.1 Msun. | ||
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| Title: | Light curves of SN 1998A and comparison with similar unusual SNe | |
| Authors: | Woodings, Simon J.; Williams, Andrew J.; Martin, Ralph; Burman, Ronald R.; Blair, David G. | |
| Journal: | Monthly Notices of the Royal Astronomical Society, Volume 301, Issue 1, pp. L5-L9. | |
| Publication Date: | 11/1998 | |
| Keywords: | SUPERNOVAE: GENERAL, SUPERNOVAE: INDIVIDUAL: SN 1998A, SUPERNOVAE: INDIVIDUAL: SN 1987A, SUPERNOVAE: INDIVIDUAL: SN 1909A, SUPERNOVAE: INDIVIDUAL: SN 1993J | |
| Abstract | ||
| Preliminary photometric data for SN 1998A are presented, showing that it increased in brightness by 1.0±0.1 mag in RI over the 80-d period following discovery. Maximum brightness occurred approximately 70 d after discovery, centred within a broad plateau-like peak lasting about 30 d. The shapes of the light curves during the entire 170-d period are similar to those of SNe 1987A and 1909A, suggesting that SNe 1998A and 1909A may also have had blue supergiant progenitors. Spectroscopic and further photometric study of SN 1998A will allow more detailed comparisons between this and other unusual Type II supernovae. | ||
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| Title: | Narrowband Photometry of Comet P/Halley: Variation with Heliocentric Distance, Season, and Solar Phase Angle | |
| Authors: | Schleicher, David G.; Millis, Robert L.; Birch, Peter V. | |
| Journal: | Icarus, Volume 132, Issue 2, pp. 397-417. | |
| Publication Date: | 04/1998 | |
| DOI: | 10.1006/icar.1997.5902 | |
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