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16571. Variability of point sources in infrared
ID:
ivo://CDS.VizieR/J/AJ/134/2099
Title:
Variability of point sources in infrared
Short Name:
J/AJ/134/2099
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a list of 552 sources with suspected variability, based on a comparison of mid-infrared photometry from the GLIMPSE I and Midcourse Space Experiment (MSX) surveys, which were carried out nearly a decade apart. We were careful to address issues such as the difference in resolution and sensitivity between the two surveys, as well as the differences in the spectral responses of the instruments. We selected only sources where the IRAC 8.0um and MSX 8.28um fluxes differ by more than a factor of 2, in order to minimize contamination from sources where the difference in fluxes at 8um is due to a strong 10um silicate feature. We present a subset of 40 sources for which additional evidence suggests variability, using 2MASS and MIPSGAL data. Based on a comparison with the variability flags in the IRAS and MSX point-source catalogs we estimate that at least a quarter of the 552 sources and at least half of the 40 sources in the subset are truly variable. In addition, we tentatively confirm the variability of one source using multiepoch IRAS LRS spectra. We suggest that most of the sources in our list are likely to be asymptotic giant branch stars.
16572. Variability of radio-bright BL Lac objects
ID:
ivo://CDS.VizieR/J/AJ/137/5022
Title:
Variability of radio-bright BL Lac objects
Short Name:
J/AJ/137/5022
Date:
21 Oct 2021
Publisher:
CDS
Description:
Radio-bright BL Lacertae objects (BLOs) are typically very variable and exhibit prominent flaring. We use a sample of 24 BLOs, regularly monitored at Metsahovi Radio Observatory, to get a clear idea of their flaring behavior in the radio domain and to find possible commonalities in their variability patterns. Our goal was to compare the results given by computational timescales and the observed variability parameters determined directly from the flux curves. Also, we wanted to find out if the BLO flares adhere to the generalized shock model, which gives a schematic explanation for the physical process giving rise to the variability. We use long-term monitoring data from 4.8, 8, 14.5, 22, 37, 90, and 230GHz, obtained mainly from the University of Michigan and Metsahovi Radio Observatories. The structure function, discrete correlation function, and Lomb-Scargle periodogram timescales, calculated in a previous study, are analyzed in more detail. Also, we determine flare durations, rise and decay times, and absolute and relative peak fluxes from the monitoring data.
16573. Variability of RSGs in M31 from the iPTF survey
ID:
ivo://CDS.VizieR/J/ApJ/859/73
Title:
Variability of RSGs in M31 from the iPTF survey
Short Name:
J/ApJ/859/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
Most massive stars end their lives as red supergiants (RSGs), a short-lived evolutionary phase when they are known to pulsate with varying amplitudes. The RSG period-luminosity (PL) relation has been measured in the Milky Way, the Magellanic Clouds and M33 for about 120 stars in total. Using over 1500 epochs of R-band monitoring from the Palomar Transient Factory survey over a five-year period, we study the variability of 255 spectroscopically cataloged RSGs in M31. We find that all RGSs brighter than M_K_~-10mag (log(L/L_{sun}_)>4.8) are variable at {Delta}m_R_>0.05mag. Our period analysis finds 63 with significant pulsation periods. Using the periods found and the known values of M_K_ for these stars, we derive the RSG PL relation in M31 and show that it is consistent with those derived earlier in other galaxies of different metallicities. We also detect, for the first time, a sequence of likely first-overtone pulsations. Comparison to stellar evolution models from MESA confirms the first-overtone hypothesis and indicates that the variable stars in this sample have 12M_{sun}_<M<24M_{sun}_. As these RSGs are the immediate progenitors to Type II-P core-collapse supernovae (SNe), we also explore the implication of their variability in the initial-mass estimates for SN progenitors based on archival images of the progenitors. We find that this effect is small compared to the present measurement errors.
16574. Variability of SDSS broad absorption line QSOs
ID:
ivo://CDS.VizieR/J/ApJ/814/150
Title:
Variability of SDSS broad absorption line QSOs
Short Name:
J/ApJ/814/150
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a qualitative analysis of the variability of quasar broad absorption lines using the large multi-epoch spectroscopic data set of the Sloan Digital Sky Survey Data Release 10. We confirm that variations of absorption lines are highly coordinated among different components of the same ion or the same absorption component of different ions for CIV, SiIV, and NV. Furthermore, we show that the equivalent widths (EWs) of the lines decrease or increase statistically when the continuum brightens or dims. This is further supported by the synchronized variations of emission and absorption-line EWs when the well-established intrinsic Baldwin effect for emission lines is taken into account. We find that the emergence of an absorption component is usually accompanied by the dimming of the continuum while the disappearance of an absorption-line component is accompanied by the brightening of the continuum. This suggests that the emergence or disappearance of a CIV absorption component is only the extreme case, when the ionic column density is very sensitive to continuum variations or the continuum variability the amplitude is larger. These results support the idea that absorption-line variability is driven mainly by changes in the gas ionization in response to continuum variations, that the line-absorbing gas is highly ionized, and in some extreme cases, too highly ionized to be detected in UV absorption lines. Due to uncertainties in the spectroscopic flux calibration, we cannot quantify the fraction of quasars with asynchronized continuum and absorption-line variations.
16575. Variability of seven blazars in six bands
ID:
ivo://CDS.VizieR/J/A+A/562/A79
Title:
Variability of seven blazars in six bands
Short Name:
J/A+A/562/A79
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the light curves of six BL Lac objects, PKS 0537-441, PKS 0735+17, OJ 287, PKS 2005-489, PKS 2155- 304, W Comae, and of the Flat Spectrum Radio Quasar PKS 1510-089, as a part of a photometric monitoring program in the near-infrared/optical bands started in 2004. All sources are Fermi Blazars. Our purpose is to investigate flux and spectral variability at short and long time scales. Systematic monitoring, independent of the activity of the source, guarantees high statistics, and allows to draw an unbiased view of different activity states on weekly/daily time scales for the whole timeframe, and on nightly timescales for some epochs. Data were obtained with the REM telescope located at the ESO premises of La Silla (Chile). Light curves were gathered in the optical/near-infrared VRIJHK bands from 2005 April to 2012 June. Variability >~3mag is observed in PKS 0537-441, PKS 1510-089 and PKS 2155-304, the largest ranges spanned in the near-infrared. The color intensity plots show rather different morphologies. The spectral energy distributions in general are well fitted by a power law, with some deviations which are more apparent in low states. Some variability episodes during a night interval are well documented for PKS 0537-441 and PKS 2155-304. For the latter source the variability time scale implies a large relativistic beaming factor.
16576. Variability of the fine-structure constant
ID:
ivo://CDS.VizieR/J/MNRAS/345/609
Title:
Variability of the fine-structure constant
Short Name:
J/MNRAS/345/609
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have previously presented evidence for a varying fine-structure constant, {alpha}, in two independent samples of Keck/HIRES quasi-stellar object (QSO) absorption spectra. Here we present a detailed many-multiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2<zabs<3.7.
16577. Variability & polarization of luminous quasars
ID:
ivo://CDS.VizieR/J/A+A/353/77
Title:
Variability & polarization of luminous quasars
Short Name:
J/A+A/353/77
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use 250 radio loud quasars with UBV photometry available and z<1.65, to study whether there is a gap in the distribution of absolute magnitudes, from M_V_~-25.8 (for H_0_=100km/s/Mpc, q_0_=0.5) to -25.3, as was suggested by Teerikorpi (1981A&A....98..309T; Paper I). In Paper I it was also proposed that there is a class of the most luminous radio quasars, differing in some properties from fainter quasars on the other side of the gap. The main conclusion of Paper I remains intact. The gap in the distribution of absolute magnitudes is confirmed with the new formalism of cosmological Malmquist bias (Teerikorpi, 1998A&A...339..647T), which allows one to use heterogeneous samples with magnitude inhomogeneity.
16578. Variability properties of TIC sources with KELT
ID:
ivo://CDS.VizieR/J/AJ/155/39
Title:
Variability properties of TIC sources with KELT
Short Name:
J/AJ/155/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Kilodegree Extremely Little Telescope (KELT) has been surveying more than 70% of the celestial sphere for nearly a decade. While the primary science goal of the survey is the discovery of transiting, large-radii planets around bright host stars, the survey has collected more than 10^6^ images, with a typical cadence between 10-30 minutes, for more than four million sources with apparent visual magnitudes in the approximate range 7<V<13. Here, we provide a catalog of 52741 objects showing significant large-amplitude fluctuations likely caused by stellar variability, as well as 62229 objects identified with likely stellar rotation periods. The detected variability ranges in rms-amplitude from ~3 mmag to ~2.3 mag, and the detected periods range from ~0.1 to >~2000 days. We provide variability upper limits for all other ~4000000 sources. These upper limits are principally a function of stellar brightness, but we achieve typical 1{sigma} sensitivity on 30 min timescales down to ~5 mmag at V~8, and down to ~43 mmag at V~13. We have matched our catalog to the TESS Input catalog and the AAVSO Variable Star Index to precipitate the follow-up and classification of each source. The catalog is maintained as a living database on the Filtergraph visualization portal at the URL https://filtergraph.com/kelt_vars.
16579. Variability Sample Catalogue from SOGS
ID:
ivo://CDS.VizieR/J/A+A/503/1023
Title:
Variability Sample Catalogue from SOGS
Short Name:
J/A+A/503/1023
Date:
21 Oct 2021
Publisher:
CDS
Description:
A set of 55000 stars brighter than about B-magnitude 14 and having at least three observations are identified in the Sydney Observatory Galactic Survey, carried out over the years 1892-1932 along the galactic equator section l{in}[275deg,335deg] with galactic latitude b{in}[-7deg,7deg]. Short-term (30min) and long-term (decades) magnitude variations in the data set are analyzed.
16580. Variability-selected AGN in CDFS
ID:
ivo://CDS.VizieR/J/A+A/497/81
Title:
Variability-selected AGN in CDFS
Short Name:
J/A+A/497/81
Date:
21 Oct 2021
Publisher:
CDS
Description:
Supermassive black holes with masses of 10^5^-10^9^M_{sun}_ are believed to inhabit most, if not all, nuclear regions of galaxies, and both observational evidence and theoretical models suggest a scenario where galaxy and black hole evolution are tightly related. Luminous AGNs are usually selected by their non-stellar colours or their X-ray emission. Colour selection cannot be used to select low-luminosity AGNs, since their emission is dominated by the host galaxy. Objects with low X-ray to optical ratio escape even the deepest X-ray surveys performed so far. In a previous study we presented a sample of candidates selected through optical variability in the Chandra Deep Field South, where repeated optical observations were performed in the framework of the STRESS supernova survey. The analysis is devoted to breaking down the sample in AGNs, starburst galaxies, and low-ionisation narrow-emission line objects, to providing new information about the possible dependence of the emission mechanisms on nuclear luminosity and black-hole mass, and eventually studying the evolution in cosmic time of the different populations.

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