Andrzej Udalski - Warsaw University Observatory

Andrzej Udalski
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Name
Andrzej Udalski
Affiliation
Warsaw University Observatory
City
Warsaw
Country
Poland

Pubs By Year

Pub Categories

 
Solar and Stellar Astrophysics (18)
 
Astrophysics (13)
 
Cosmology and Nongalactic Astrophysics (8)
 
Earth and Planetary Astrophysics (8)
 
Astrophysics of Galaxies (7)
 
High Energy Astrophysical Phenomena (5)
 
Instrumentation and Methods for Astrophysics (4)

Publications Authored By Andrzej Udalski

2016Aug
Affiliations: 1Michigan St., 2Michigan St., 3Michigan St., 4Alberta, 5Warsaw, 6Michigan St., 7Michigan St., 8Michigan St.

We report the discovery of an eclipsing low-mass X-ray binary at the center of the 3FGL error ellipse of the unassociated Fermi/Large Area Telescope gamma-ray source 3FGL J0427.9-6704. Photometry from OGLE and the SMARTS 1. Read More

Located in the Small Magellanic Cloud (SMC), SXP214 is an X-ray pulsar in a high mass X-ray binary system with a Be-star companion. A recent survey of the SMC under a Chandra X-ray Visionary program found the source in a transition when the X-ray flux was on a steady rise. The Lomb-Scargle periodogram revealed a pulse period of 211. Read More

Recently, the discovery of a Venus-mass planet orbiting a brown-dwarf host in a binary system was reported from the analysis of the microlensing event OGLE-2013-BLG-0723. We reanalyze the event considering the possibility of other interpretations. From this, we find a new solution where the lens is composed of 2 bodies in contrast to the 3-body solution of the previous analysis. Read More

Real-time analysis and classification of observational data collected within synoptic sky surveys is a huge challenge due to constant growth of data volumes. Machine learning techniques are often applied in order to perform this task automatically. The current bottleneck of transients detection in most surveys is the process of filtering numerous artifacts from candidate detection. Read More

The microlensing event OGLE-2015-BLG-0448 was observed by Spitzer and lay within the tidal radius of the globular cluster NGC 6558. The event had moderate magnification and was intensively observed, hence it had the potential to probe the distribution of planets in globular clusters. We measure the proper motion of NGC 6558 ($\mu_{\rm cl}$(N,E) = (+0. Read More

We investigate interstellar extinction curve variations toward $\sim$4 deg$^{2}$ of the inner Milky Way in $VIJK_{s}$ photometry from the OGLE-III and $VVV$ surveys, with supporting evidence from diffuse interstellar bands and $F435W,F625W$ photometry. We obtain independent measurements toward $\sim$2,000 sightlines of $A_{I}$, $E(V-I)$, $E(I-J)$, and $E(J-K_{s})$, with median precision and accuracy of 2%. We find that the variations in the extinction ratios $A_{I}/E(V-I)$, $E(I-J)/E(V-I)$ and $E(J-K_{s})/E(V-I)$ are large (exceeding 20%), significant, and positively correlated, as expected. Read More

We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay (BRAVA-RR), which has the unusual radial velocity of -372 +- 8 km/s and true space velocity of -482 +- 22 km/s relative to the Galactic rest frame. Read More

We model the split red clump of the Galactic bulge in OGLE-III photometry, and compare the results to predictions from two N-body models. Our analysis yields precise maps of the brightness of the two red clumps, the fraction of stars in the more distant peak, and their combined surface density. We compare the observations to predictions from two N-body models previously used in the literature. Read More

We report on the discovery of a new Small Magellanic Cloud (SMC) symbiotic star, OGLE-SMC-LPV-00861, previously catalogued as H$\alpha$ emission line source LIN 9. The OGLE light curve shows multiple-maxima outburst behaviour over $\sim$1200 d with a maximum outburst of $\Delta V=1.5$ mag. Read More

We observed RX J0520.5-6932 in the X-rays and studied the optical light curve of its counterpart to verify it as a Be/X-ray binary. We performed an XMM-Newton anticipated target of opportunity observation in January 2013 during an X-ray outburst of the source in order to search for pulsations and derive its spectral properties. Read More

We present and study the largest and the most comprehensive catalog of microlensing events ever constructed. The sample of standard microlensing events comprises 3718 unique events from years 2001--2009, with 1409 not detected before in real-time by the Early Warning System of the Optical Gravitational Lensing Experiment (OGLE). The search pipeline makes use of Machine Learning algorithms in order to help find rare phenomena among 150 million objects and derive the detection efficiency. Read More

We report the serendipitous discovery of a disk-eclipse system OGLE-LMC-ECL-11893. The eclipse occurs with a period of 468 days, a duration of about 15 days and a deep (up to \Delta I ~1.5), peculiar and asymmetric profile. Read More

2013Dec
Affiliations: 1Warsaw University Observatory, 2Warsaw University Observatory, 3Warsaw University Observatory, 4Warsaw University Observatory, 5Warsaw University Observatory, 6Warsaw University Observatory, 7Ohio State University, 8Warsaw University Observatory, 9Warsaw University Observatory, 10Warsaw University Observatory, 11Warsaw University Observatory, 12Ohio State University

We develop a new method to measure source proper motions in microlensing events, which can partially overcome problems due to blending. It takes advantage of the fact that the source position is known precisely from the microlensing event itself. We apply this method to the event MOA-2011-BLG-262, which has a short timescale t_E=3. Read More

We present a distance determination to the Small Magellanic Cloud (SMC) based on an analysis of four detached, long period, late type eclipsing binaries discovered by the OGLE Survey. The components of the binaries show negligible intrinsic variability. A consistent set of stellar parameters was derived with low statistical and systematic uncertainty. Read More

The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) have been observed. The targets were selected from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on their optical variability, mid-IR and/or X-ray properties. Read More

Symbiotic stars are interacting binaries with the longest orbital periods and their multi-component structure makes them rich astrophysical laboratories. The accretion of a high mass loss rate red giant wind on to a white dwarf (WD) makes them promising Type Ia supernovae (SNe Ia) progenitors. Systematic surveys for new Galactic symbiotic stars are critical to identify new promising SNe Ia progenitors (e. Read More

2013May

Symbiotic stars are the longest orbital period interacting binaries, where nova-like outbursts are generated by the accretion of a high mass loss rate red giant wind onto a white dwarf companion. Long-term photometric monitoring surveys such as OGLE and MACHO are ideal platforms to identify nova-like events in symbiotic stars, however there are only a handful of known systems within the small footprint of these surveys. We introduce a systematic Halpha emission line object survey for new symbiotic stars covering 35 deg^2 towards the Galactic Bulge that combines deep 2dF/AAOmega spectroscopy with OGLE and MACHO photometry. Read More

Microlensing experiments are returning increasingly detailed information about the planetary and binary systems that are being detected, far beyond what was originally expected. In several cases the lens mass and distance are measured, and a few very special cases have yielded complete 8-parameter Kepler solutions, i.e. Read More

We report the analysis of a highly magnetised neutron star in the Large Magellanic Cloud (LMC). The high mass X-ray binary pulsar Swift J045106.8-694803 has been observed with Swift X-ray telescope (XRT) in 2008, the Rossi X-ray Timing Explorer (RXTE) in 2011 and the X-ray Multi-Mirror Mission - Newton (XMM-Newton) in 2012. Read More

We combine VI photometry from OGLE-III with VVV and 2MASS measurements of E(J-K_{s}) to resolve the longstanding problem of the non-standard optical extinction toward the Galactic bulge. We show that the extinction is well-fit by the relation A_{I} = 0.7465*E(V-I) + 1. Read More

We present a multi-wavelength analysis of the very fast X-ray transient MAXI J0158-744, which was detected by MAXI/GSC on 2011 November 11. The subsequent exponential decline of the X-ray flux was followed with Swift observations, all of which revealed spectra with low temperatures (~100eV) indicating that MAXI J0158-744 is a new Supersoft Source (SSS). The Swift X-ray spectra near maximum show features around 0. Read More

2012Feb
Affiliations: 1OSU, 2OSU, 3Warsaw University Observatory, 4Warsaw University Observatory

The damped random walk (DRW) model is increasingly used to model the variability in quasar optical light curves, but it is still uncertain whether the DRW model provides an adequate description of quasar optical variability across all time scales. Using a sample of OGLE quasar light curves, we consider four modifications to the DRW model by introducing additional parameters into the covariance function to search for deviations from the DRW model on both short and long time scales. We find good agreement with the DRW model on time scales that are well sampled by the data (from a month to a few years), possibly with some intrinsic scatter in the additional parameters, but this conclusion depends on the statistical test employed and is sensitive to whether the estimates of the photometric errors are correct to within ~10%. Read More

We present the broadest and most precise empirical investigation of red giant branch bump (RGBB) brightness and number counts ever conducted. We implement a new method and use data from two \textit{Hubble Space Telescope (HST)} globular cluster (GC) surveys to measure the brightness and star counts of the RGBB in 72 GCs. The brightness is measured to a precision better than 0. Read More

About 2500 square degrees of sky south of declination -25 degrees and/or near the galactic plane were surveyed for bright outer solar system objects. This survey is one of the first large scale southern sky and galactic plane surveys to detect dwarf planets and other bright Kuiper Belt objects in the trans-Neptunian region. The survey was able to obtain a limiting R-band magnitude of 21. Read More

We measure the intrinsic magnitude dispersion of the Galactic bulge red clump (RC) using two different methods and arrive at an estimate of \sigma_{I} ~ 0.17 mag. We first estimate the width of the RC by analyzing in detail a sample of RC measurements toward double RC sightlines, which are toward regions of the bulge that are geometrically thin. Read More

2011Feb
Affiliations: 1Warsaw University Observatory, 2The Ohio State University, 3Warsaw University Observatory

We report the spectroscopic confirmation of 29 new, 12 plausible, and 3 previously known quasars behind the central ~1.5 deg^2 region of the Small Magellanic Cloud. These were identified in a single 2df/AAOmega observation on the Anglo-Australian Telescope of 268 candidates selected primarily based on their mid-IR colors, along with a smaller number of optically variable sources in OGLE-II close to known X-ray sources. Read More

At present, microlensing light curves from different telescopes and filters are photometrically aligned by fitting them to a common model. We present a second method based on photometry of common field stars. If two spectral responses are similar (or the color of the source is known) then this technique can resolve important ambiguities that frequently arise when predicting the future course of the event, and that occasionally persist even when the event is over. Read More

We present a high-resolution spectrum of a microlensed G dwarf in the Galactic bulge with spectroscopic temperature T_eff = 5600 +/- 180 K. This I~21 mag star was magnified by a factor ranging from 1160 to 1300 at the time of observation. Its high metallicity ([Fe/H] = 0. Read More

2008Apr
Affiliations: 1OGLE, MicroFUN, MOA, PLANET/RoboNET, 2OGLE, MicroFUN, MOA, PLANET/RoboNET, 3OGLE, MicroFUN, MOA, PLANET/RoboNET, 4OGLE, MicroFUN, MOA, PLANET/RoboNET, 5OGLE, MicroFUN, MOA, PLANET/RoboNET, 6OGLE, MicroFUN, MOA, PLANET/RoboNET, 7OGLE, MicroFUN, MOA, PLANET/RoboNET, 8OGLE, MicroFUN, MOA, PLANET/RoboNET, 9OGLE, MicroFUN, MOA, PLANET/RoboNET, 10OGLE, MicroFUN, MOA, PLANET/RoboNET, 11OGLE, MicroFUN, MOA, PLANET/RoboNET, 12OGLE, MicroFUN, MOA, PLANET/RoboNET, 13OGLE, MicroFUN, MOA, PLANET/RoboNET, 14OGLE, MicroFUN, MOA, PLANET/RoboNET, 15OGLE, MicroFUN, MOA, PLANET/RoboNET, 16OGLE, MicroFUN, MOA, PLANET/RoboNET, 17OGLE, MicroFUN, MOA, PLANET/RoboNET, 18OGLE, MicroFUN, MOA, PLANET/RoboNET, 19OGLE, MicroFUN, MOA, PLANET/RoboNET, 20OGLE, MicroFUN, MOA, PLANET/RoboNET, 21OGLE, MicroFUN, MOA, PLANET/RoboNET, 22OGLE, MicroFUN, MOA, PLANET/RoboNET, 23OGLE, MicroFUN, MOA, PLANET/RoboNET, 24OGLE, MicroFUN, MOA, PLANET/RoboNET, 25OGLE, MicroFUN, MOA, PLANET/RoboNET, 26OGLE, MicroFUN, MOA, PLANET/RoboNET, 27OGLE, MicroFUN, MOA, PLANET/RoboNET, 28OGLE, MicroFUN, MOA, PLANET/RoboNET, 29OGLE, MicroFUN, MOA, PLANET/RoboNET, 30OGLE, MicroFUN, MOA, PLANET/RoboNET, 31OGLE, MicroFUN, MOA, PLANET/RoboNET, 32OGLE, MicroFUN, MOA, PLANET/RoboNET, 33OGLE, MicroFUN, MOA, PLANET/RoboNET, 34OGLE, MicroFUN, MOA, PLANET/RoboNET, 35OGLE, MicroFUN, MOA, PLANET/RoboNET, 36OGLE, MicroFUN, MOA, PLANET/RoboNET, 37OGLE, MicroFUN, MOA, PLANET/RoboNET, 38OGLE, MicroFUN, MOA, PLANET/RoboNET, 39OGLE, MicroFUN, MOA, PLANET/RoboNET, 40OGLE, MicroFUN, MOA, PLANET/RoboNET, 41OGLE, MicroFUN, MOA, PLANET/RoboNET, 42OGLE, MicroFUN, MOA, PLANET/RoboNET, 43OGLE, MicroFUN, MOA, PLANET/RoboNET, 44OGLE, MicroFUN, MOA, PLANET/RoboNET, 45OGLE, MicroFUN, MOA, PLANET/RoboNET, 46OGLE, MicroFUN, MOA, PLANET/RoboNET, 47OGLE, MicroFUN, MOA, PLANET/RoboNET, 48OGLE, MicroFUN, MOA, PLANET/RoboNET, 49OGLE, MicroFUN, MOA, PLANET/RoboNET, 50OGLE, MicroFUN, MOA, PLANET/RoboNET, 51OGLE, MicroFUN, MOA, PLANET/RoboNET, 52OGLE, MicroFUN, MOA, PLANET/RoboNET, 53OGLE, MicroFUN, MOA, PLANET/RoboNET, 54OGLE, MicroFUN, MOA, PLANET/RoboNET, 55OGLE, MicroFUN, MOA, PLANET/RoboNET, 56OGLE, MicroFUN, MOA, PLANET/RoboNET, 57OGLE, MicroFUN, MOA, PLANET/RoboNET, 58OGLE, MicroFUN, MOA, PLANET/RoboNET, 59OGLE, MicroFUN, MOA, PLANET/RoboNET, 60OGLE, MicroFUN, MOA, PLANET/RoboNET, 61OGLE, MicroFUN, MOA, PLANET/RoboNET, 62OGLE, MicroFUN, MOA, PLANET/RoboNET, 63OGLE, MicroFUN, MOA, PLANET/RoboNET, 64OGLE, MicroFUN, MOA, PLANET/RoboNET, 65OGLE, MicroFUN, MOA, PLANET/RoboNET, 66OGLE, MicroFUN, MOA, PLANET/RoboNET, 67OGLE, MicroFUN, MOA, PLANET/RoboNET, 68OGLE, MicroFUN, MOA, PLANET/RoboNET, 69OGLE, MicroFUN, MOA, PLANET/RoboNET, 70OGLE, MicroFUN, MOA, PLANET/RoboNET, 71OGLE, MicroFUN, MOA, PLANET/RoboNET, 72OGLE, MicroFUN, MOA, PLANET/RoboNET, 73OGLE, MicroFUN, MOA, PLANET/RoboNET, 74OGLE, MicroFUN, MOA, PLANET/RoboNET, 75OGLE, MicroFUN, MOA, PLANET/RoboNET, 76OGLE, MicroFUN, MOA, PLANET/RoboNET, 77OGLE, MicroFUN, MOA, PLANET/RoboNET, 78OGLE, MicroFUN, MOA, PLANET/RoboNET, 79OGLE, MicroFUN, MOA, PLANET/RoboNET, 80OGLE, MicroFUN, MOA, PLANET/RoboNET, 81OGLE, MicroFUN, MOA, PLANET/RoboNET, 82OGLE, MicroFUN, MOA, PLANET/RoboNET, 83OGLE, MicroFUN, MOA, PLANET/RoboNET, 84OGLE, MicroFUN, MOA, PLANET/RoboNET
Category: Astrophysics

We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first in a high-magnification event. These include photometric and astrometric measurements from Hubble Space Telescope, as well as constraints from higher order effects extracted from the ground-based light curve, such as microlens parallax, planetary orbital motion and finite-source effects. Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is an M dwarf in the foreground disk with mass M= 0. Read More

We present precise V and Ks-band transit photometry for the planetary host star OGLE-TR-113. Using the Ks-band photometry, we confirm the dwarf nature of OGLE-TR-113, and obtain new estimates for its effective temperature, distance and reddening. We employ the V-band photometry to obtain planetary and orbit parameters from the transit fit, a= (0. Read More

We present accurate V-band photometry for a planetary transit of OGLE-TR-111 acquired with VIMOS at the ESO Very Large Telescope. The measurement of this transit allows to refine the planetary radius, obtaining R_p= 1.01 +/- 0. Read More

Transiting planets are essential to study the structure and evolution of extra-solar planets. For that purpose, it is important to measure precisely the radius of these planets. Here we report new high-accuracy photometry of the transits of OGLE-TR-10 and OGLE-TR-56 with VLT/FORS1. Read More

2006Aug
Affiliations: 1Ohio State, 2Caltech, 3San Diego State, 4Caltech, 5Warsaw University Observatory, 6Ohio State
Category: Astrophysics

We present an R=45,000 Keck spectrum of the microlensed Galactic bulge G-dwarf OGLE-2006-BLG-265, which has a high (~60) signal-to-noise ratio despite its short (15 min) exposure time because the source was magnified by A~135. While it is very metal-rich ([Fe/H]=0.56), the higher temperature of this star compared with the luminous red giants usually measured in the bulge gives its spectrum many unblended atomic lines. Read More

We present the results of HST observations of the host star for the first definitive extrasolar planet detected by microlensing. The light curve model for this event predicts that the lens star should be separated from the source star by ~6mas at the time of the HST images. If the lens star is a late G, K or early M dwarf, then it will be visible in the HST images as an additional source of light that is blended with the source image. Read More

We present precise V-band photometry for the low-amplitude transit candidate star OGLE-TR-109. This is an extreme case among the transiting candidates found by the OGLE group because of the early spectral type of the star (F0V), of the low transit amplitude (A_I=0.008 mag), and of the very short period (P=0. Read More

We derive the frequencies of hot Jupiters (HJs) with 3--5 day periods and very hot Jupiters (VHJs) with 1-3 day periods by comparing the planets actually detected in the OGLE-III survey with those predicted by our models. The models are constructed following Gould & Morgan (2003) by populating the line of sight with stars drawn from the Hipparcos catalog. Using these, we demonstrate that the number of stars with sensitivity to HJs and VHJs is only 4--16% of those in the OGLE-III fields satisfying the spectroscopic-followup limit of V_max<17. Read More

2005Jun
Affiliations: 1Ohio State, 2Max-Planck fuer Astronomie, 3Notre Dame, 4CEA Saclay, 5Ohio State, 6Warsaw University Observatory, 7Warsaw University Observatory
Category: Astrophysics

We attempt to identify all microlensing parallax events for which the parallax fit improves \Delta\chi^2 > 100 relative to a standard microlensing model. We outline a procedure to identify three types of discrete degeneracies (including a new one that we dub the ``ecliptic degeneracy'') and find many new degenerate solutions in 16 previously published and 6 unpublished events. Only four events have one unique solution and the other 18 events have a total of 44 solutions. Read More

We present an algorithm that can detect blends of bright stars with fainter, un-associated eclipsing binaries. Such systems contaminate searches for transiting planets, in particular in crowded fields where blends are common. Spectroscopic follow-up observations on large aperture telescopes have been used to reject these blends, but the results are not always conclusive. Read More

We report the independent discovery of a new extrasolar transiting planet around OGLE-TR-113, a candidate star from the Optical Gravitational Lensing Experiment. Small radial-velocity variations have been detected based on observations conducted with the MIKE spectrograph on the Magellan I (Baade) telescope at the Las Campanas Observatory (Chile) during 2003. We have also carried out a light-curve analysis incorporating new photometry and realistic physical parameters for the star. Read More

2002Apr
Affiliations: 1Villanova Univ. & Univ. Barcelona, 2Villanova Univ., 3Villanova Univ., 4Villanova Univ., 5Warsaw University
Category: Astrophysics

We present results from a detailed analysis of a third eclipsing binary (EB) system in the Large Magellanic Cloud, EROS 1044 (~B2 IV-V + ~B2 III-IV). Our study combines the "classical" EB study of light and radial velocity curves with detailed modeling of the observed spectral energy distribution, and yields an essentially complete picture of the stellar properties of the system and a determination of its distance. The observational data exploited include optical photometry, space-based UV spectroscopy, and UV/optical spectrophotometry. Read More