- ID:
- ivo://CDS.VizieR/J/ApJ/806/258
- Title:
- Optical LCs of QSO J0924+0219 lensed quasar
- Short Name:
- J/ApJ/806/258
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the optical, UV, and X-ray microlensing variability of the lensed quasar SDSS J0924+0219 using six epochs of Chandra data in two energy bands (spanning 0.4-8.0keV, or 1-20keV in the quasar rest frame), 10 epochs of F275W (rest-frame 1089{AA}) Hubble Space Telescope data, and high-cadence R-band (rest-frame 2770{AA}) monitoring spanning 11 years. Our joint analysis provides robust constraints on the extent of the X-ray continuum emission region and the projected area of the accretion disk. The best-fit half-light radius of the soft X-ray continuum emission region is between 5x10^13^ and 10^15^cm, and we find an upper limit of 10^15^cm for the hard X-rays. The best-fit soft-band size is about 13 times smaller than the optical size, and roughly 7GM_BH_/C^2^ for a 2.8x10^8^M_{sun}_ black hole, similar to the results for other systems. We find that the UV emitting region falls in between the optical and X-ray emitting regions at 10^14^cm<r_1/2.UV_<3x10^15^cm. Finally, the optical size is significantly larger, by 1.5{sigma}, than the theoretical thin-disk estimate based on the observed, magnification-corrected I-band flux, suggesting a shallower temperature profile than expected for a standard disk.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/662/62
- Title:
- Optical monitoring of SDSS J1004+4112
- Short Name:
- J/ApJ/662/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 426 epochs of optical monitoring data spanning 1000 days from 2003 December to 2006 June for the gravitationally lensed quasar SDSS J1004+4112. The time delay between the A and B images is {Delta}t_BA_=38.4+/-2.0days ({Delta}{chi}^2^=4) in the expected sense that B leads A and the overall time ordering is C-B-A-D-E. The measured delay invalidates all published models. The models probably failed because they neglected the perturbations from cluster member galaxies. Models including the galaxies can fit the data well, but conclusions about the cluster mass distribution should await the measurement of the longer, and less substructure sensitive, delays of the C and D images. For these images, a delay of {Delta}t_CB_~=681+/-15days is plausible but requires confirmation, while delays of {delta}t_CB_>560days and {delta}t_AD_>800 days are required. We clearly detect microlensing of the A/B images, with the delay-corrected flux ratios changing from mB-mA=0.44+/-0.01mag in the first season to 0.29+/-0.01mag in the second season and 0.32+/-0.01mag in the third season.
- 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/AJ/162/203
- Title:
- Photometry of OGLE-2019-BLG-0304 with OGLE & KMTNet
- Short Name:
- J/AJ/162/203
- Date:
- 01 Feb 2022 07:08:03
- Publisher:
- CDS
- Description:
- We analyze the microlensing event OGLE-2019-BLG-0304, whose light curve exhibits two distinctive features: a deviation in the peak region and a second bump appearing ~61days after the main peak. Although a binary-lens model can explain the overall features, it leaves subtle but noticeable residuals in the peak region. We find that the residuals can be explained by the presence of either a planetary companion located close to the primary of the binary lens (3L1S model) or an additional close companion to the source (2L2S model). Although the 3L1S model is favored over the 2L2S model, with {Delta}{chi}2~8, securely resolving the degeneracy between the two models is difficult with the currently available photometric data. According to the 3L1S interpretation, the lens is a planetary system, in which a planet with a mass 0.51_-0.23_^+0.51^M_J_ is in an S-type orbit around a binary composed of stars with masses 0.27_-0.12_^+0.27^M{odot} and 0.10_-0.04_^+0.10^M{odot}. According to the 2L2S interpretation, however, the source is composed of G- and K-type giant stars and the lens is composed of a low-mass M dwarf and a brown dwarf with masses 0.12_-0.05_^+0.12^M{odot} and 0.045_-.019_^+0.045^M{odot}, respectively. The event illustrates the need for thorough model testing in the interpretation of lensing events with complex features in light curves.
- 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.
- ID:
- ivo://CDS.VizieR/J/AcA/68/351
- Title:
- Predicted Microlensing Events by nearby VLM objects
- Short Name:
- J/AcA/68/351
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Microlensing events can be used to directly measure the masses of single field stars to a precision of ~1-10%. The majority of direct mass measurements for stellar and sub-stellar objects typically only come from observations of binary systems. Hence microlensing provides an important channel for direct mass measurements of single stars. The Gaia satellite has observed ~1.7 billion objects, and analysis of the second data release has recently yielded numerous event predictions for the next few decades. However, the Gaia catalog is incomplete for nearby very-low-mass objects such as brown dwarfs for which mass measurements are most crucial. We employ a catalog of very-low-mass objects from Pan-STARRS data release 1 (PDR1) as potential lens stars, and we use the objects from Gaia data release 2 (GDR2) as potential source stars. We then search for future microlensing events up to the year 2070. The Pan-STARRS1 objects are first cross-matched with GDR2 to remove any that are present in both catalogs. This leaves a sample of 1718 possible lenses. We fit MIST isochrones to the Pan-STARRS1, AllWISE and 2MASS photometry to estimate their masses. We then compute their paths on the sky, along with the paths of the GDR2 source objects, until the year 2070, and search for potential microlensing events. Source-lens pairs that will produce a microlensing signal with an astrometric amplitude of greater than 0.131mas, or a photometric amplitude of greater than 0.4mmag, are retained.
- ID:
- ivo://CDS.VizieR/J/AcA/68/183
- Title:
- Predicted Microlensing Events for the 21st Century
- Short Name:
- J/AcA/68/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Gaia data release 2 (GDR2, Cat. I/345), we present an almanac of 2509 predicted microlensing events, caused by 2130 unique lens stars, that will peak between July 25, 2026 and the end of the century. This work extends and completes a thorough search for future microlensing events initiated by Bramich and Nielsen using GDR2. The almanac includes 161 lenses that will cause at least two microlensing events each. All of the predicted microlensing events in the almanac will exhibit astrometric signals that are detectable by observing facilities with an angular resolution and astrometric precision similar to, or better than, that of the Hubble Space Telescope (e.g., NIRCam on the James Webb Space Telescope), although the events with the most extreme source-to-lens contrast ratios may be challenging. Ground-based telescopes of at least 1 m in diameter can be used to observe many of the events that are also expected to exhibit a photometric signal.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A44
- Title:
- Predicted microlensing events from Gaia DR2
- Short Name:
- J/A+A/618/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I search for source-lens pairs in Gaia Data Release 2 (GDR2, Cat. I/345) that could potentially lead to microlensing events between 25th July 2014 and 25th July 2026. I estimate the lens masses using GDR2 photometry and parallaxes, and appropriate model stellar isochrones. Combined with the source and lens parallax measurements from GDR2, this allows the Einstein ring radius to be computed for each source-lens pair. By considering the source and lens paths on the sky, I calculate the microlensing signals that are to be expected.
