- ID:
- ivo://CDS.VizieR/J/AcA/51/175
- Title:
- OGLE-II DIA microlensing events
- Short Name:
- J/AcA/51/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of microlensing events discovered in the Difference Image Analysis (DIA) of the OGLE-II images collected during three observing seasons, 1997-1999. 4424 light curves pass our criteria on the presence of a brightening episode on top of a constant baseline. Among those, 512 candidate microlensing events were selected visually. We designed an automated procedure, which unambiguously selects up to 237 best events. Including eight candidate events recovered by other means, a total of 520 light curves are presented in this work.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/216/12
- Title:
- OGLE-III Galactic bulge microlensing events
- Short Name:
- J/ApJS/216/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and study the largest and most comprehensive catalog of microlensing events ever constructed. The sample of standard microlensing events comprises 3718 unique events from 2001-2009 with 1409 events that had not been detected before in real-time by the Early Warning System of the Optical Gravitational Lensing Experiment. The search pipeline uses machine learning algorithms to help find rare phenomena among 150 million objects and to derive the detection efficiency. Applications of the catalog can be numerous, from analyzing individual events to large statistical studies of the Galactic mass, kinematics distributions, and planetary abundances. We derive maps of the mean Einstein ring crossing time of events spanning 31 deg^2^ toward the Galactic center and compare the observed distributions with the most recent models. We find good agreement within the observed region and we see the signature of the tilt of the bar in the microlensing data. However, the asymmetry of the mean timescales seems to rise more steeply than predicted, indicating either a somewhat different orientation of the bar or a larger bar width. The map of events with sources in the Galactic bulge shows a dependence of the mean timescale on the Galactic latitude, signaling an increasing contribution from disk lenses closer to the plane relative to the height of the disk. Our data present a perfect set for comparing and enhancing new models of the central parts of the Milky Way and creating a three-dimensional picture of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A20
- Title:
- OGLE-III parallax events with Gaia DR2
- Short Name:
- J/A+A/636/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context. Gravitational microlensing is sensitive to compact-object lenses in the Milky Way, including white dwarfs, neutron stars, or black holes, and could potentially probe a wide range of stellar-remnant masses. However, the mass of the lens can be determined only in very limited cases, due to missing information on both source and lens distances and their proper motions. Aims. Our aim is to improve the mass estimates in the annual parallax microlensing events found in the eight years of OGLE-III observations towards the Galactic Bulge with the use of Gaia Data Release 2 (DR2). Methods. We use Gaia DR2 data on distances and proper motions of non-blended sources and recompute the masses of lenses in parallax events. We also identify new events in that sample which are likely to have dark lenses; the total number of such events is now 18. Results. The derived distribution of masses of dark lenses is consistent with a continuous distribution of stellar-remnant masses. A mass gap between neutron star and black hole masses in the range between 2 and 5 solar masses is not favoured by our data, unless black holes receive natal kicks above 20-80km/s. We present eight candidates for objects with masses within the putative mass gap, including a spectacular multi-peak parallax event with mass of 2.4_-1.3_^+1.9^M_{sun}_ located just at 600pc. The absence of an observational mass gap between neutron stars and black holes, or conversely the evidence of black hole natal kicks if a mass gap is assumed, can inform future supernova modelling efforts.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/3012
- Title:
- OGLE-III Parallax microlensing events
- Short Name:
- J/MNRAS/458/3012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most stellar remnants so far have been found in binary systems, where they interact with matter from their companions. Isolated neutron stars and black holes are difficult to find as they are dark, yet they are predicted to exist in our Galaxy in vast numbers. We explored the OGLE-III data base of 150 million objects observed in years 2001-2009 and found 59 microlensing events exhibiting a parallax effect due to the Earth's motion around the Sun. Combining parallax and brightness measurements from microlensing light curves with expected proper motions in the Milky Way, we identified 13 microlensing events which are consistent with having a white dwarf, neutron star or a black hole lens and we estimated their masses and distances. The most massive of our black hole candidates has 9.3M_{sun}_ and is at a distance of 2.4kpc. The distribution of masses of our candidates indicates a continuum in mass distribution with no mass gap between neutron stars and black holes. We also present predictions on how such events will be observed by the astrometric Gaia mission.
- ID:
- ivo://CDS.VizieR/J/ApJ/636/240
- Title:
- OGLE II microlensing parameters
- Short Name:
- J/ApJ/636/240
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a measurement of the microlensing optical depth toward the Galactic bulge based on 4 years of the OGLE-II survey. We consider only bright sources in the extended red clump giant (RCG) region of the color-magnitude diagram, in 20 bulge fields covering ~5deg^2^ between 0{deg}<l<3{deg} and -4{deg}<b<-2{deg}. Using a sample of 32 events we find {tau}=2.55x10^-6^ at (l,b)=(1.16{deg},-2.75{deg}).
- ID:
- ivo://CDS.VizieR/J/AcA/50/1
- Title:
- OGLE microlensing events in Galactic Bulge
- Short Name:
- J/AcA/50/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Catalog of microlensing events detected toward the Galactic bulge in three observing seasons, 1997-1999, during the OGLE-II microlensing survey. The search for microlensing events was performed using a database of about 4x10^9^ photometric measurements of about 20.5 million stars from the Galactic bulge. The Catalog comprises 214 microlensing events found in the fields covering about 11 square degrees on the sky and distributed in different parts of the Galactic bulge. The sample includes 20 binary microlensing events, 14 of them are caustic crossing. In one case a double star is likely lensed. We present distribution of the basic parameters of microlensing events and show preliminary rate of microlensing in different regions of the Galactic bulge. The latter reveals clear dependence on the Galactic coordinates. The dependence on l indicates that the majority of lenses toward the Galactic bulge are located in the Galactic bar. Models of the Galactic bar seem to reasonably predict the observed spatial distribution of microlensing events in the Galactic bulge. All data presented in the Catalog and photometry of all events are available from the OGLE Internet archive.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A163
- Title:
- Pan-STARRS lens candidates from neural networks
- Short Name:
- J/A+A/644/A163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a systematic search for wide-separation (with Einstein radius ~1.5"), galaxy-scale strong lenses in the 30000 sq.deg of the Pan-STARRS 3pi survey on the Northern sky. With long time delays of a few days to weeks, these types of systems are particularly well-suited for catching strongly lensed supernovae with spatially-resolved multiple images and offer new insights on early-phase supernova spectroscopy and cosmography. We produced a set of realistic simulations by painting lensed COSMOS sources on Pan-STARRS image cutouts of lens luminous red galaxies (LRGs) with redshift and velocity dispersion known from the sloan digital sky survey (SDSS). First, we computed the photometry of mock lenses in gri bands and applied a simple catalog-level neural network to identify a sample of 1050207 galaxies with similar colors and magnitudes as the mocks. Second, we trained a convolutional neural network (CNN) on Pan-STARRS gri image cutouts to classify this sample and obtain sets of 105760 and 12382 lens candidates with scores of pCNN>0.5 and >0.9, respectively. Extensive tests showed that CNN performances rely heavily on the design of lens simulations and the choice of negative examples for training, but little on the network architecture. The CNN correctly classified 14 out of 16 test lenses, which are previously confirmed lens systems above the detection limit of Pan-STARRS. Finally, we visually inspected all galaxies with pCNN>0.9 to assemble a final set of 330 high-quality newly-discovered lens candidates while recovering 23 published systems. For a subset, SDSS spectroscopy on the lens central regions proves that our method correctly identifies lens LRGs at z~0.1-0.7. Five spectra also show robust signatures of high-redshift background sources, and Pan-STARRS imaging confirms one of them as a quadruply-imaged red source at z_s_=1.185, which is likely a recently quenched galaxy strongly lensed by a foreground LRG at z_d_=0.3155. In the future, high-resolution imaging and spectroscopic follow-up will be required to validate Pan-STARRS lens candidates and derive strong lensing models. We also expect that the efficient and automated two-step classification method presented in this paper will be applicable to the ~4 mag deeper gri stacks from the Rubin Observatory Legacy Survey of Space and Time (LSST) with minor adjustments.
- ID:
- ivo://CDS.VizieR/J/A+A/501/461
- Title:
- Photometric masses of early-type lens galaxies
- Short Name:
- J/A+A/501/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The largest spectroscopically selected sample of strong gravitational lens systems presented and analyzed to date is that of the Sloan Lens ACS (SLACS) survey. For the 57 massive early-type lens galaxies in the sample, photometric and spectroscopic measurements are available from the Sloan Digital Sky Survey (SDSS). By using the SDSS multicolor photometry and lens modeling, we study stellar-mass properties and the luminous and dark matter composition of the early-type lens galaxies in the sample.
- ID:
- ivo://CDS.VizieR/J/A+A/402/1157
- Title:
- Photometric standards around gravitational lenses
- Short Name:
- J/A+A/402/1157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of secondary photometric standard stars in the neighborhood of 14 gravitationally lensed quasars. These stars were verified to be non variable using long-term monitoring. The instrumental magnitudes of the new standard stars have been transformed to the Johnson-Cousins BV(RI)c photometric system. For ten gravitational lenses (GLs) we also provide the BV(RI)c mean magnitudes of the integrated flux of all the lens components, for the epochs of the photometric calibration.
- ID:
- ivo://CDS.VizieR/J/other/Nat/481.167
- Title:
- 2002-2007 PLANET microlensing events
- Short Name:
- J/other/Nat/481.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17-30% of solar-like stars host a planet. Gravitational microlensing on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002-07) that reveals the fraction of bound planets 0.5-10AU (Sun-Earth distance) from their stars. We find that of stars host Jupiter-mass planets (0.3-10M<SUB>J</SUB>, where M<SUB>J</SUB>=318M<SUB>{earth}</SUB> and M<SUB>{earth}</SUB> is Earth's mass). Cool Neptunes (10-30M<SUB>{earth}</SUB>) and super-Earths (5-10M<SUB>{earth}</SUB>) are even more common: their respective abundances per star are 52<SUP>+22</SUP><SUB>–29</SUB>% and 62<SUP>+35</SUP><SUB>–37</SUB>%. We conclude that stars are orbited by planets as a rule, rather than the exception.
