- ID:
- ivo://CDS.VizieR/J/ApJS/186/233
- Title:
- Variable point sources in SDSS stripe 82. I.
- Short Name:
- J/ApJS/186/233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first results of a study of variable point sources identified using multi-color timeseries photometry from Sloan Digital Sky Survey (SDSS) Stripe 82, including data from the SDSS-II Supernova Survey, over a span of nearly 10 years (1998-2007). We construct a light-curve catalog of 221842 point sources in the R.A. 0-4hr half of Stripe 82, limited to r=22.0mag, that have at least 10 detections in the ugriz bands and color errors <0.2mag. These sources are then classified by color and by cross matching them to existing SDSS catalogs of interesting objects. Inhomogeneous ensemble differential photometry techniques are used to greatly improve our sensitivity to variability and reduce contamination by sources that appear variable due to large photometric noise or systematic effects caused by non-uniform photometric conditions throughout the survey. We use robust variable identification methods to extract 6520 variable candidates from this data set, resulting in an overall variable fraction of ~2.9% at the level of ~0.05mag variability. Despite the sparse and uneven time sampling of the light-curve data, we discover 143 periodic variables in total. Due to period ambiguity caused by relatively poor phase coverage, we identify a smaller final set of 101 periodic variables with well-determined periods and light curves. Among these are 55 RR Lyrae, 30 eclipsing binary candidates, and 16 high-amplitude Delta Scuti variables. In addition to these objects, we also identify a sample of 2704 variable quasars matched to the SDSS Quasar Catalog, which make up a large fraction of our variable candidates. An additional 2403 quasar candidates are tentatively identified and selected by their non-stellar colors and variability. A sample of 11328 point sources that appear to be nonvariable given the limits of our variability sensitivity is also briefly discussed. Finally, we describe several interesting objects discovered among our eclipsing binary candidates, and illustrate the use of our publicly available light-curve catalog by tracing Galaxy halo substructure with our small sample of RR Lyrae variables.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/633/638
- Title:
- Variable quasar sample from SDSS
- Short Name:
- J/ApJ/633/638
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SDSS repeat spectroscopic observations have resulted in multiepoch spectroscopy for 2500 quasars observed more than 50 days apart. From this sample, calibrating against stars observed simultaneously, we identify 315 quasars that have varied significantly between observations (with respect to assumed nonvariable stars observed concurrently). These variable quasars range in redshift from 0.5 to 4.72. This is the first large quasar sample studied spectroscopically for variability and represents a potentially useful sample for future high-redshift reverberation mapping studies. This also marks the first time the precise wavelength dependence of quasar variability has been determined, allowing both the continuum and emission-line variability to be studied.
- ID:
- ivo://CDS.VizieR/J/MNRAS/498/5972
- Title:
- Variables and dippers in young associations
- Short Name:
- J/MNRAS/498/5972
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young associations in star-forming regions are stellar systems that allow us to understand the mechanisms that characterize the stars in their early life and what happens around them. In particular, the analysis of the discs and of the exoplanets around young stars allows us to know the key processes that prevail in their evolution and understand the properties of the exoplanets orbiting older stars. The Transiting Exoplanet Survey Satellite mission is giving us the opportunity to extract and analyse the light curves of association members with high accuracy, but the crowding that affects these regions makes difficult the light curve extraction. In the PATHOS project, cutting-edge tools are used to extract high-precision light curves and identify variable stars and transiting exoplanets in open clusters and associations. In this work, I analysed the light curves of stars in five young (<10Myr) associations, searching for variables and candidate exoplanets. Using the rotational periods of the association members, I constrained the ages of the five stellar systems (~2-10Myr). I searched for dippers, and I investigated the properties of the dust that forms the circumstellar discs. Finally, I searched for transiting signals, finding six strong candidate exoplanets. No candidates with radius Rp<0.9R_J_ have been detected, in agreement with the expectations. The frequency of giant planets resulted to be ~2-3 per cent, higher than that expected for field stars (<1 per cent); the low statistic makes this conclusion not strong, and new investigations on young objects are mandatory to confirm this result.
- ID:
- ivo://CDS.VizieR/J/A+AS/90/451
- Title:
- Variables and Nebulae in Sgr B
- Short Name:
- J/A+AS/90/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/ApJS/175/191
- Title:
- Variables from 2MASS calibration fields
- Short Name:
- J/ApJS/175/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Two Micron All Sky Survey (2MASS) photometric calibration observations cover ~6 square degrees on the sky in 35 "calibration fields", each sampled in nominal photometric conditions between 562 and 3692 times during the 4 years of the 2MASS mission. We compile a catalog of variables from the calibration observations to search for M dwarfs transited by extrasolar planets. We present our methods for measuring periodic and nonperiodic flux variability. From 7554 sources with apparent K_s_ magnitudes between 5.6 and 16.1, we identify 247 variables, including extragalactic variables and 23 periodic variables. We have discovered three M dwarf eclipsing systems, including two candidates for transiting extrasolar planets.
- ID:
- ivo://CDS.VizieR/J/A+A/537/A116
- Title:
- Variables in Centaurus field F170
- Short Name:
- J/A+A/537/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used deep V-band and JHKs-band observations to investigate variability and stellar populations near the Galactic plane in Centaurus, and compare the observations with the Galactic model of Besancon. By applying image subtraction technique to a series of over 580 V-band frames taken with the ESO VLT/VIMOS instrument during two contiguous nights in April 2005 we have detected 333 variables among 84,734 stars in the brightness range 12.7<V<26.0mag. Infrared data collected in March 2010 with the new ESO VISTA telescope allowed us to construct deep combined optical-IR colour-magnitude and colour-colour diagrams. All detected variables but four transit candidates are reported for the first time. The majority of the variables are eclipsing/ellipsoidal binaries and delta Scuti-type pulsators. The occurrence rate of eclipsing/ellipsoidal variables reached ~0.28% of all stars. This is very close to the highest fraction of binary systems detected using ground-based data so far (0.30%), but still about four times smaller than the average occurrence rate recently obtained from the Kepler space mission after 44 days of operation. Comparison of the observed Ks vs. V-Ks diagram with a diagram based on the Besancon model shows significant effects of both distance and reddening in the investigated direction of the sky. We demonstrate that the best model indicates presence of absorbing clouds at distances 11-13kpc from the Sun in the minor Carina-Sagittarius Arm.
7637. Variables in Cygnus OB2
- ID:
- ivo://CDS.VizieR/J/MNRAS/298/753
- Title:
- Variables in Cygnus OB2
- Short Name:
- J/MNRAS/298/753
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the photometric CCD search for B-type variables in the central region of the Cygnus OB2 association. We discover 29 new variables including two Beta Cephei stars. The photometric data in the Cousins I band are given in file photom.dat. In addition, we present BV(RI)c and H_{alpha}_ photometry for stars in the observed field. This is Table 4 of the paper, available only in electronic form.
- ID:
- ivo://CDS.VizieR/J/AJ/120/284
- Title:
- Variables in Leo II dwarf spheroidal
- Short Name:
- J/AJ/120/284
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first comprehensive catalog of variable stars in the Leo II dwarf spheroidal galaxy. We have identified 148 RR Lyrae type variables, of which 140 were amenable to derivation of variability parameters with our data. We have also confirmed the existence of four anomalous Cepheids as identified in previous studies. The average period of the RR Lyrae ab variables (0.62 days), the fraction of c variables (0.24), and the minimum period of the RR Lyrae ab variables (0.51 days) all define Leo II as an "Oosterhoff intermediate" galaxy. We have used the properties of these variables to derive a metallicity for Leo II of approximately [Fe/H]=-1.9.
- ID:
- ivo://CDS.VizieR/J/AJ/145/160
- Title:
- Variables in LMC globular clusters. III. Reticulum
- Short Name:
- J/AJ/145/160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the third in a series of papers studying the variable stars in old globular clusters in the Large Magellanic Cloud. The primary goal of this series is to look at how the characteristics and behavior of RR Lyrae stars in Oosterhoff-intermediate systems compare to those of their counterparts in Oosterhoff-I/II systems. In this paper we present the results of our new time-series BVI photometric study of the globular cluster Reticulum. We found a total of 32 variables stars (22 RRab, 4 RRc, and 6 RRd stars) in our field of view. We present photometric parameters and light curves for these stars. We also present physical properties, derived from Fourier analysis of light curves, for some of the RR Lyrae stars. We discuss the Oosterhoff classification of Reticulum and use our results to re-derive the distance modulus and age of the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/144/186
- Title:
- Variables in LMC globular clusters. II. NGC 1786
- Short Name:
- J/AJ/144/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B-V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters.
