- ID:
- ivo://CDS.VizieR/J/A+A/525/A37
- Title:
- Variability indexes of QSOs in SDSS Stripe 82
- Short Name:
- J/A+A/525/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identified 8744 quasars in the Light-Motion Curve Catalogue (LMCC; Bramich et al., 2008MNRAS.386..887B, http://das.sdss.org/value_added/stripe_82_variability/SDSS_82_public/) for the stripe 82 of the Sloan Digital Sky Survey (SDSS). The light curves were used, after correction for photometric outliers, to compute individual noise-corrected first-order structure functions (variance as a function of time-lag) binned into rest frame time-lag intervals. The mean value of the corrected structure function at rest frame time-lags from 300 to 600 days is found to be a useful variability index for the statistical investigation of quasar samples with redshifts up to ~3. For each quasar, the variability indexes for the five SDSS bands are given along with the equatorial coordinates, redshift, mean g band magnitude, absolute i band magnitude, and a remark on spectral peculiarities.
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- ID:
- ivo://CDS.VizieR/J/ApJ/901/9
- Title:
- Variability in protoplanetary nebulae. VII. 5 LCs
- Short Name:
- J/ApJ/901/9
- Date:
- 15 Feb 2022 13:25:51
- Publisher:
- CDS
- Description:
- We have monitored over a 10-year interval the light variations of five evolved stars with very large mid-infrared excesses. All five objects appear to have oxygen-rich or mixed oxygen-rich and carbon-rich chemistries. They all vary in light: four over a small range of ~0.2mag and the fifth over a larger range of ~0.7mag. Spectral types range from G2 to B0. Periodic pulsations are found for the first time in the three cooler ones, IRAS18075-0924 (123d), 19207+2023 (96d), and 20136+1309 (142d). No significant periodicity is found in the hotter ones, but they appear to vary on a shorter timescale of a few days or less. Two also show some evidence of longer-term periodic variations (~4yr). Three appear to be protoplanetary nebulae (PPNe), in the post-asymptotic giant branch (post-AGB) phase of stellar evolution. Their light variations are in general agreement with the relationships among temperature, pulsation period, and pulsation amplitude found in previously studied PPNe. The other two, however, appear to have too low a luminosity (1000-1500L_{sun}_), based on Gaia distances, to be in the post-AGB phase. Instead, they appear to be Milky Way analogs of the recently identified class of dusty post-red giant branch (post-RGB) stars found in the Magellanic Clouds, which likely had their evolution interrupted by interaction with a binary companion. If this is the case, then these would be among the first dusty post-RGB objects identified in the the Milky Way.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/116
- Title:
- Variability in proto-PNe. II.
- Short Name:
- J/ApJ/766/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a detailed observational study of the light, color, and velocity variations of two bright, carbon-rich proto-planetary nebulae, IRAS 22223+4327 and 22272+5435. The light curves are based upon our observations from 1994 to 2011, together with published data by Arkhipova and collaborators. They each display four significant periods, with primary periods for IRAS 22223+4327 and 22272+5435 being 90 and 132 days, respectively. For each of them, the ratio of secondary to primary period is 0.95, a value much different from that found in Cepheids, but which may be characteristic of post-asymptotic giant branch (AGB) stars. Fewer significant periods are found in the smaller radial velocity data sets, but they agree with those of the light curves. The color curves generally mimic the light curves, with the objects reddest when faintest. A comparison in seasons when there exist contemporaneous light, color, and velocity curves reveals that the light and color curves are in phase, while the radial velocity curves are ~0.25 P out of phase with the light curves. Thus they differ from what is seen in Cepheids, in which the radial velocity curve is 0.50 P out of phase with the light curve. Comparison of the observed periods and amplitudes with those of post-AGB pulsation models shows poor agreement, especially for the periods, which are much longer than predicted. These observational data, particularly the contemporaneous light, color, and velocity curves, provide an excellent benchmark for new pulsation models of cool stars in the post-AGB, proto-planetary nebula phase.
- ID:
- ivo://CDS.VizieR/J/AJ/147/70
- Title:
- Variability in TAOS I. 58 new variable stars
- Short Name:
- J/AJ/147/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Taiwanese-American Occultation Survey project is designed for the detection of stellar occultations by small-size Kuiper Belt Objects, and it has monitored selected fields along the ecliptic plane by using four telescopes with a 3deg^2^ field of view on the sky since 2005. We have analyzed data accumulated during 2005-2012 to detect variable stars. Sixteen fields with observations of more than 100 epochs were examined. We recovered 85 variables among a total of 158 known variable stars in these 16 fields. Most of the unrecovered variables are located in the fields observed less frequently. We also detected 58 variable stars which are not listed in the International Variable Star Index of the American Association of Variable Star Observers. These variable stars are classified as 3 RR Lyrae, 4 Cepheid, 1 {delta} Scuti, 5 Mira, 15 semi-regular, and 27 eclipsing binaries based on the periodicity and the profile of the light curves.
- ID:
- ivo://CDS.VizieR/J/A+A/403/247
- Title:
- Variability in the ROSAT All-Sky Survey
- Short Name:
- J/A+A/403/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a systematic search for variability among the ROSAT All-Sky Survey (RASS) X-ray sources. We generated lightcurves for about 30000 X-ray point sources detected sufficiently high above background. For our variability study different search algorithms were developed in order to recognize flares, periods and trends, respectively. The variable X-ray sources were optically identified with counterparts in the SIMBAD, the USNO-A2.0 and NED data bases, but a significant part of the X-ray sources remains without cataloged optical counterparts. A complete list of the 1207 variable sources we found is presented here.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A125
- Title:
- Variability of A- and F-stars from Kepler
- Short Name:
- J/A+A/534/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars, and observationally investigate the relation between {gamma} Doradus ({gamma} Dor), {delta} Scuti ({delta} Sct), and hybrid stars.
- ID:
- ivo://CDS.VizieR/J/A+A/461/183
- Title:
- Variability of classical T Tauri
- Short Name:
- J/A+A/461/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a study the long term variability of Classical T Tauri stars (CTTS) over up to 20 years, characterize it from a set of statistical parameters and discuss its origin. We characterize the long term photometric variations of 49 CTTs with sufficient data for allowing a robust statistical analysis and propose an empirical classification scheme. Several patterns of long term photometric variability are identified. The most common pattern, exhibited by a group of 15 stars which includes T Tau itself, consists of low level variability (with V-amplitude less than 0.4mag) with no significant changes occurring from season to season over many years. A related subgroup of 22 stars exhibit a similar stable long term variability pattern, though with larger amplitudes (up to 1.6mag). Besides these representative groups, we identify three smaller groups of 3-5 stars each of which have distinctive photometric properties. The long term variability of most CTTS is fairly stable and merely reflects shorter term variability due to cold and hot surface spots. Only a small fraction of CTTS undergo significant brightness changes on the long term (months, years), which probably arise from slowly varying circumstellar extinction.
- ID:
- ivo://CDS.VizieR/J/AZh/78/408
- Title:
- Variability of Cyg X-1 in 1994-1998
- Short Name:
- J/AZh/78/408
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric UBVR photometry of Cyg X-1 obtained during the coordinated international campaign 'Optical Monitoring of Unique Astrophysical objects', carried out in observatories of CIS countries (Georgia, Kazakhstan, Russia, Uzbekistanin and Ukraine) 1994-1998 is presented. The data are presented as a single set, taking into account systematic differences between individual data sets. In total 2258 UBVR observations were obtained during 407 nights.
- ID:
- ivo://CDS.VizieR/J/PAZh/26/27
- Title:
- Variability of Cyg X-1 (V1357) in 1995-1996
- Short Name:
- J/PAZh/26/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric UBVR photometry of Cyg X-1 with 1-m Tian'-Shan' and 48-cm Maidanak Observatory reflectors from October 1995 through November 1996 are presented.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/1061
- Title:
- Variability of FBS blue stellar objects
- Short Name:
- J/MNRAS/415/1061
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new method for combined calculations of magnitudes based on accurate measurements of POSS1 and POSS2 epoch plates is given. The photometric accuracy of various surveys and catalogs has been estimated and established and statistical weights for each of them have been calculated. To achieve the best possible magnitudes, weighted averaging of data from USNO-A2.0, APM, MAPS, USNO-B1.0, and GSC 2.3.2 catalogs have been used. The rms accuracy of magnitudes achieved for POSS1 is 0.184 mag for B and 0.173 mag for R and for POSS2 is 0.138 mag for B and 0.128 mag for R. We have derived the best POSS1 and POSS2 magnitudes for the FBS blue stellar objects. We have refined the transformation formulae between the POSS1 and POSS2 magnitudes and SDSS ones and standard UBV system. Using these accurate magnitudes, we have estimated the variability of the FBS blue stellar objects and revealed probable and possible variables. We have worked out methods to control and exclude accidental errors that appear in any survey. We have compared and combined our results with those given in NSVS database and obtained better candidates for variability. Having excluded variables, we have combined POSS1 and POSS2 data for the rest of objects to achieve even better magnitudes and colors; the rms being smaller than 0.1 mag both in B and R and for the B-R colors. This approach has been applied to the First Byurakan Survey blue stellar objects containing significant number of white dwarfs, cataclysmic variables, as well as extragalactic objects (quasars, Seyferts, BL Lac objects). Altogether 336 variable objects have been revealed with POSS2-POSS1 >= 3{sigma} of the errors. An electronic table of these objects is given. Candidate variables are divided into 4 classes: extreme, strong, probable and possible variables. For a more reliable sample of variable objects we excluded possible ones from the list and were left with 161 objects. Analyzing radio and X-ray properties of these objects, we have revealed their nature and re-discovered or revealed candidate AGN, CVs, WDs and other objects.
