- ID:
- ivo://CDS.VizieR/J/MNRAS/465/L114
- Title:
- OGLE16aaa UVOT light curves
- Short Name:
- J/MNRAS/465/L114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery and first three months of follow-up observations of a currently on-going unusual transient detected by the Optical Gravitational Lensing Experiment (OGLE-IV) survey, located in the centre of a galaxy at redshift z=0.1655. The long rise to absolute magnitude of -20.5mag, slow decline, very broad He and H spectral features make OGLE16aaa similar to other optical/UV tidal disruption events (TDEs). Weak narrow emission lines in the spectrum and archival photometric observations suggest the host galaxy is a weak-line active galactic nucleus, which has been accreting at higher rate in the past. OGLE16aaa, along with SDSS J0748, seems to form a sub-class of TDEs by weakly or recently active supermassive black holes (SMBHs). This class might bridge the TDEs by quiescent SMBHs and flares observed as "changing-look quasars", if we interpret the latter as TDEs. If this picture is true, the previously applied requirement for identifying a flare as a TDE that it had to come from an inactive nucleus, could be leading to observational bias in TDE selection, thus affecting TDE-rate estimations.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/385/905
- Title:
- OGLEII high pm stars towards Galactic Centre
- Short Name:
- J/MNRAS/385/905
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photometry data base of the second phase of the OGLE microlensing experiment, OGLE-II, is a rich source of information about the kinematics and structure of the Galaxy. In this work, we use the OGLE-II proper motion catalogue to identify candidate stars which have high proper motions. 521 stars with proper motion {mu}>50mas/yr in the OGLE-II proper motion catalogue were cross-identified with stars in the MACHO high proper motion catalogue, and the DEep Near-Infrared Survey and Two-Micron All-Sky Survey infrared photometry catalogues. Photometric distances were computed for stars with colours consistent with G/K- and M-type stars. Six stars were newly identified as possible nearby (<50pc) M dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/61
- Title:
- OGLE-III, MCPS and HST VI obs. of LMC & SMC
- Short Name:
- J/ApJ/886/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a calibration of the tip of the red giant branch (TRGB) in the Large Magellanic Cloud (LMC) on the Hubble Space Telescope (HST)/ACS F814W system. We use archival HST observations to derive blending corrections and photometric transformations for two ground-based wide-area imaging surveys of the Magellanic Clouds. We show that these surveys are biased bright by up to ~0.1mag in the optical due to blending, and that the bias is a function of local stellar density. We correct the LMC TRGB magnitudes from Jang & Lee (2017ApJ...835...28J) and use the geometric distance from Pietrzynski+ (2019Natur.567..200P) to obtain an absolute TRGB magnitude of M_F814W_=-3.97+/-0.046mag. Applying this calibration to the TRGB magnitudes from Freedman+ (2019ApJ...882...34F) in SN Ia hosts yields a value for the Hubble constant of H_0_=72.4+/-2.0km/s/Mpc for their TRGB+SNe Ia distance ladder. The difference in the TRGB calibration and the value of H_0_ derived here and by Freedman+ primarily results from their overestimate of the LMC extinction, caused by inconsistencies in their different sources of TRGB photometry for the Magellanic Clouds. Using the same source of photometry (OGLE) for both Clouds and applying the aforementioned corrections yields a value for the LMC I-band TRGB extinction that is lower by 0.06mag, consistent with independent OGLE reddening maps used by us and by Jang & Lee to calibrate TRGB and determine H0.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/20
- Title:
- OGLE-III Mira variables in the Magellanic Clouds
- Short Name:
- J/ApJ/884/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Period-Luminosity and Period-Luminosity-Color relations at maximum light for Mira variables in the Magellanic Clouds using time-series data from the Optical Gravitational Lensing Experiment (OGLE-III) and Gaia data release 2. The maximum-light relations exhibit a scatter typically up to ~30% smaller than their mean-light counterparts. The apparent magnitudes of oxygen-rich Miras at maximum light display significantly smaller cycle-to-cycle variations than at minimum light. High-precision photometric data for Kepler Mira candidates also exhibit stable magnitude variations at the brightest epochs, while their multi-epoch spectra display strong Balmer emission lines and weak molecular absorption at maximum light. The stability of maximum-light magnitudes for Miras possibly occurs due to the decrease in the sensitivity to molecular bands at their warmest phase. At near-infrared wavelengths, the period-luminosity relations (PLRs) of Miras display similar dispersion at mean and maximum light with limited time-series data in the Magellanic Clouds. A kink in the oxygen-rich Mira PLRs is found at 300 days in the VI-bands, which shifts to longer periods (~350 days) at near-infrared wavelengths. Oxygen-rich Mira PLRs at maximum light provide a relative distance modulus, {Delta}{mu}=0.48+/-0.08mag, between the Magellanic Clouds with a smaller statistical uncertainty than the mean-light relations. The maximum-light properties of Miras can be very useful for stellar atmosphere modeling and distance scale studies provided their stability and the universality can be established in other stellar environments in the era of extremely large telescopes.
- ID:
- ivo://CDS.VizieR/J/AcA/63/379
- Title:
- OGLE-III variable stars in Galactic disk area
- Short Name:
- J/AcA/63/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for pulsating stars in the 7.12deg^2^ OGLE-III Galactic disk area in the direction tangent to the Centaurus Arm. We report the identification of 20 Classical Cepheids, 45 RR Lyr type stars, 31 Long-Period Variables, such as Miras and Semi-Regular Variables, one pulsating white dwarf, and 58 very likely {delta} Sct type stars. Based on asteroseismic models constructed for one quadruple-mode and six triple-mode {delta} Sct type pulsators, we estimated masses, metallicities, ages, and distance moduli to these objects. The modeled stars have masses in the range 0.9-2.5M_{sun}_ and are located at distances between 2.5kpc and 6.2kpc. Two triple-mode and one double-mode pulsators seem to be Population II stars of the SX Phe type, probably from the Galactic halo. Our sample also includes candidates for Type II Cepheids and unclassified short-period (P<0.23d) multi-mode stars which could be either {delta}Sct or {beta}Cep type stars. One of the detected variables is a very likely {delta} Sct star with an exceptionally high peak-to-peak I-band amplitude of 0.35mag at the very short period of 0.0196d. All reported pulsating variable stars but one object are new discoveries. They are included in the OGLE-III Catalog of Variable Stars. Finally, we introduce the on-going OGLE-IV Galactic Disk Survey, which covers more than half of the Galactic plane. For the purposes of future works on the spiral structure and star formation history of the Milky Way, we have already compiled a list of known Galactic Classical Cepheids.
- ID:
- ivo://CDS.VizieR/J/AcA/48/289
- Title:
- OGLE-I long-period and non-periodic variables
- Short Name:
- J/AcA/48/289
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a list of long-period and non-periodic variable stars detected in the OGLE-I database. These stars were not included in previous catalogs of periodic stars found in OGLE data. The catalog contains 116 stars in twelve Baade's Window fields and additionally in the Galactic bulge fields: MM1/5/7-A/B, MM3 and GB1.
- ID:
- ivo://CDS.VizieR/J/AJ/159/262
- Title:
- OGLE/KMTnet VI bands photomerty of OGLE-2019-BLG-0551
- Short Name:
- J/AJ/159/262
- Date:
- 08 Dec 2021
- Publisher:
- CDS
- Description:
- High-cadence observations of the Galactic bulge by the microlensing surveys led to the discovery of a handful of extremely short-timescale microlensing events that can be attributed to free-floating or wide-orbit planets. Here, we report the discovery of another strong free-floating planet candidate, which was found from the analysis of the gravitational microlensing event OGLE-2019-BLG-0551. The light curve of the event is characterized by a very short duration (<~3days) and a very small amplitude (<~0.1mag). From modeling of the light curve, we find that the Einstein timescale, t_E_=0.381{+/-}0.017day, is much shorter, and the angular Einstein radius, {theta}_E_=4.35{+/-}0.34{mu}mas, is much smaller than those of typical lensing events produced by stellar-mass lenses (t_E_~20days, {theta}_E_~0.3mas), indicating that the lens is very likely to be a planetary-mass object. We conduct an extensive search for possible signatures of a companion star in the light curve of the event, finding no significant evidence for the putative host star. For the first time, we also demonstrate that the angular Einstein radius of the lens does not depend on blending in the low-magnification events with strong finite source effects.
2118. OGLE LMC BVI photometry
- ID:
- ivo://CDS.VizieR/J/AcA/50/307
- Title:
- OGLE LMC BVI photometry
- Short Name:
- J/AcA/50/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the BVI photometric maps of the Large Magellanic Cloud. They contain BVI photometry and astrometry of more than 7 million stars from the central parts of the LMC. The data were collected during the second phase of the OGLE microlensing project. We discuss the accuracy of the data and present color-magnitude diagrams of all 26 fields observed by OGLE in the LMC. The BVI maps of the LMC are accessible electronically for the astronomical community from the OGLE Internet archive.
- ID:
- ivo://CDS.VizieR/J/MNRAS/436/953
- Title:
- OGLE-LMC-CEP-0227 RV and VI[3.6] curves
- Short Name:
- J/MNRAS/436/953
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A novel method of analysis of double-lined eclipsing binaries containing a radially pulsating star is presented. The combined pulsating-eclipsing light curve is built up from a purely eclipsing light-curve grid created using an existing modelling tool. For every pulsation phase, the instantaneous radius and surface brightness are taken into account, being calculated from the disentangled radial velocity curve of the pulsating star and from its out-of-eclipse pulsational light curve and the light ratio of the components, respectively. The best model is found using the Markov chain Monte Carlo method. The method is applied to the eclipsing binary Cepheid OGLE-LMC-CEP-0227 (P_puls_=3.80d, P_orb_=309d). We analyse a set of new spectroscopic and photometric observations for this binary, simultaneously fitting OGLE V-band, I-band and Spitzer 3.6{mu}m photometry. We derive a set of fundamental parameters of the system significantly improving the precision comparing to the previous results obtained by our group. The Cepheid mass and radius are M_1_=4.165+/-0.032M_{sun}_ and R_1_=34.92+/-0.34R{sun}, respectively. For the first time a direct, geometrical and distance-independent determination of the Cepheid projection factor is presented. The value p=1.21+/-0.03(stat.)+/-0.04(syst.) is consistent with theoretical expectations for a short-period Cepheid and interferometric measurements for {delta} Cep. We also find a very high value of the optical limb darkening coefficients for the Cepheid component, in strong disagreement with theoretical predictions for static atmospheres at a given surface temperature and gravity.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/30
- Title:
- OGLE LMC-T2CEP-211 eclipsing binary LCs and RVs
- Short Name:
- J/ApJ/868/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of a peculiar W Virginis (pWVir) type II Cepheid, OGLE-LMC-T2CEP-211 (P_puls_=9.393d), in a double-lined binary system (P_orb_=242d), which shed light on virtually unknown evolutionary status and structure of pWVir stars. The dynamical mass of the Cepheid (first ever for a type II Cepheid) is 0.64+/-0.02M_{sun}_, and the radius R=25.1+/-0.3R_{sun}_. The companion is a massive (5.67M_{sun}_) main-sequence star obscured by a disk. Such a configuration suggests a mass transfer in the system history. We found that originally the system (P_orb_^init^=12d) was composed of 3.5 and 2.8M_{sun}_ stars, with the current Cepheid being more massive. The system age is now ~200Myr, and the Cepheid is almost completely stripped of hydrogen, with helium mass of ~92% of the total mass. It finished transferring the mass 2.5Myr ago and is evolving toward lower temperatures passing through the instability strip. Comparison with observations indicates a reasonable 2.7x10^-8^M_{sun}_/yr mass loss from the Cepheid. The companion is most probably a Be main-sequence star with T=22000K and R=2.5R_{sun}_. Our results yield a good agreement with a pulsation theory model for a hydrogen-deficient pulsator, confirming the described evolutionary scenario. We detected a two-ring disk (R_disk_~116R_{sun}_) and a shell (R_shell_~9R_{sun}_) around the companion, which is probably a combination of the matter from the past mass transfer, the mass being lost by the Cepheid owing to wind and pulsations, and a decretion disk around a rapidly rotating secondary. Our study, together with observational properties of pWVir stars, suggests that the majority of them are products of a similar binary evolution interaction.
