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- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/856/38
- Title:
- Optical LCs of the counterpart to IC 10 X-2
- Short Name:
- J/ApJ/856/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an optical and infrared (IR) study of IC 10 X-2, a high-mass X-ray binary in the galaxy IC 10. Previous optical and X-ray studies suggest that X-2 is a Supergiant Fast X-ray Transient: a large-amplitude (factor of ~100), short-duration (hours to weeks) X-ray outburst on 2010 May 21. We analyze R- and g-band light curves of X-2 from the intermediate Palomar Transient Factory taken between 2013 July 15 and 2017 February 14 that show high-amplitude (>~1mag), short-duration (<~8days) flares and dips (>~0.5mag). Near-IR spectroscopy of X-2 from Palomar/TripleSpec show He I, Paschen-{gamma}, and Paschen-{beta} emission lines with similar shapes and amplitudes as those of luminous blue variables (LBVs) and LBV candidates (LBVc). Mid-IR colors and magnitudes from Spitzer/Infrared Array Camera photometry of X-2 resemble those of known LBV/LBVcs. We suggest that the stellar companion in X-2 is an LBV/LBVc and discuss possible origins of the optical flares. Dips in the optical light curve are indicative of eclipses from optically thick clumps formed in the winds of the stellar counterpart. Given the constraints on the flare duration (0.02-0.8 days) and the time between flares (15.1+/-7.8days), we estimate the clump volume filling factor in the stellar winds, f_V_, to be 0.01<f_V_<0.71, which overlaps with values measured from massive star winds. In X-2, we interpret the origin of the optical flares as the accretion of clumps formed in the winds of an LBV/LBVc onto the compact object.
- ID:
- ivo://CDS.VizieR/J/AJ/159/61
- Title:
- Optical LCs & spectrum of the RCB star ZTF18abhjrcf
- Short Name:
- J/AJ/159/61
- Date:
- 07 Mar 2022 07:17:25
- Publisher:
- CDS
- Description:
- R Coronae Borealis stars (RCBs) constitute a rare class of stars that are hydrogen depleted and carbon enriched, possibly from white dwarf mergers. RCBs are identified by their stochastic dimming with photometric variations of as much as eight magnitudes. Hence, the discoveries of RCBs were heavily biased to the limited regions monitored by long-term microlensing experiments. However, recent studies of galactic RCBs have shown that they exhibit distinct mid-infrared colors originating from their cool circumstellar shells. The all-sky Wide-field Infrared Survey Explorer (WISE) survey thus facilitates the identification of RCB candidates. Therefore, combining the WISE colors with large-area time-domain surveys will enable us to discover more RCBs. Here we present the results of a first attempt to identify RCBs in the public Zwicky Transient Facility (ZTF) alert stream, using the alert broker ANTARES. We identify a candidate RCB using the infrared color selection by Tisserand+, 2013A&A...551A..77T and large light curve variations in the optical from ZTF. We then conduct subsequent observations using the FLOYDS spectrograph at the Las Cumbres Observatory and confirm ZTF18abhjrcf as a bona fide RCB. This demonstrates the potential to discover uncharted RCBs as ZTF and other time-domain surveys continue to operate.
- ID:
- ivo://CDS.VizieR/J/ApJS/213/26
- Title:
- Optical light curves of PHL1811 and 3C273
- Short Name:
- J/ApJS/213/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variability is one of the most observable characteristics of active galactic nuclei, and it is important when considering the emission mechanism. In this paper, we report optical photometry monitoring of two nearby brightest quasars, PHL 1811 and 3C 273, using the ST-6 camera attached to the Newtonian focus and the Ap6E CCD camera attached to the primary focus of the 70cm meniscus telescope at the Abastumani Observatory, Georgia. PHL 1811 was monitored during the period from 2002 September to 2012 December, while 3C 273 was monitored during the period from 1998 February to 2008 May. During our monitoring period, the two sources did not show any significant intra-day variability. The largest detected variations are {Delta}R=0.112+/-0.010mag. for PHL 1811, {Delta}B=0.595+/-0.099mag, {Delta}V=0.369+/-0.028mag, {Delta}R=0.495+/-0.076mag, and {Delta}I=0.355+/-0.009mag for 3C 273. When the periodicity analysis methods are adopted for the observations of the sources, a period of p=5.80+/-1.12yr is obtained for PHL 1811 in the R light curve in the present work, and periods of p=21.10+/-0.14, 10.00+/-0.14, 7.30+/-0.09, 13.20+/-0.09, 2.10+/-0.06, and 0.68+/-0.05yr are obtained for 3C 273 based on the data in the present work combined with historical works.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A90
- Title:
- Optically bright post-AGB population of LMC
- Short Name:
- J/A+A/530/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a catalogue of the optically bright post-AGB stars in the LMC. The sample forms an ideal testbed for stellar evolution theory predictions of the final phase of low- and intermediate-mass stars, because the distance and hence luminosity and also the current and initial mass of these objects is well constrained.
- ID:
- ivo://CDS.VizieR/J/other/JAD/24.3
- Title:
- Optically Variable Quasars in AllWISE/PS1
- Short Name:
- J/other/JAD/24.3
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- This catalog presents a sample of 229236 optically variable quasar candidates identified in the AllWISE and Pan-STARRS1 data releases at 2-sigma and 3-sigma variability levels. Mid-IR bands (3.4, 4.6, 12 and 22um) are selected from the AllWISE data release, and 5 optical bands (grizy) are from Pan-STARRS1. 127350 quasars are found to be variable at the 3-sigma level.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/511
- Title:
- Optical microvariability of S5 0716+714
- Short Name:
- J/ApJS/185/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We monitored the BL Lac object S5 0716+714 in the optical band during 2008 October and December and 2009 February with a best temporal resolution of about 5 minutes in the BVRI bands. Four fast flares were observed with amplitudes ranging from 0.3 to 0.75mag. The source remained active during the whole monitoring campaign, showing microvariability in all days except for one. The overall variability amplitudes are {Delta}B~0.89, {Delta}V~0.80, {Delta}R~0.73, and {Delta}I~0.51mag. Typical timescales of microvariability range from 2 to 8hr. The overall V-R color index ranges from 0.37 to 0.59. Strong bluer-when-brighter chromatism was found on internight timescales. However, a different spectral behavior was found on intranight timescales. A possible time lag of ~11 minutes between B and I bands was found on one night. The shock-in-jet model and geometric effects can be applied to explain the source's intranight behavior.
- ID:
- ivo://CDS.VizieR/J/A+A/431/779
- Title:
- Optical/near-IR atlas of OH/IR stars
- Short Name:
- J/A+A/431/779
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present optical and near-infrared finding charts, accurate astrometry (~1") and single-epoch near-infrared photometry for 371 IRAS sources, 96% of those included in the so-called "Arecibo sample of OH/IR stars" (Eder et al., 1988ApJS...66..183E; Lewis et al., 1990ApJ...362..634L; Chengalur et al., 1993, Cat. <J/ApJS/89/189>). The main photometric properties of the stars in the sample are presented and discussed as well as the problems found during the process of identification of the optical/near-infrared counterparts. In addition, we also identify suitable reference stars in each field to be used for differential photometry purposes in the future.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A60
- Title:
- Optical-NIR catalog of AKARI NEP Deep Field
- Short Name:
- J/A+A/566/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an 8-band (u*, g', r', i', z', Y, J, Ks) optical to near-infrared deep photometric catalogue based on the observations made with MegaCam and WIRCam at CFHT, and compute photometric redshifts, zph in the North Ecliptic Pole (NEP) region, where AKARI infrared satellite carried out deep survey at near to mid infrared wavelength. We designed the catalogue to include sources detected in z' band with counterparts in at least one of the other bands, and found 85797 sources in the NEP field. Comparing with galaxy spectroscopic redshifts, photometric redshift dispersion {sigma}({Delta}z/(1+z)) is 0.032 and catastrophic failure rate {Delta}z/(1+z)>0.15 is 5.8% at z<1. Our redshifts are highly accurate with z'<22 at zph<2.5 and for fainter sources with z'<24 at z<1.
