- ID:
- ivo://CDS.VizieR/J/AJ/129/2232
- Title:
- Variable stars in And I and And III
- Short Name:
- J/AJ/129/2232
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of variable star searches of the M31 dwarf spheroidal (dSph) companions Andromeda I and Andromeda III using the Hubble Space Telescope. A total of 100 variable stars were found in And I, while 56 were found in And III. One variable found in And I and another in And III may be type II Cepheids. In addition to this variable in And III, another four variables are anomalous Cepheids (ACs). So far, no definite ACs have been discovered in And I.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/124/1464
- Title:
- Variable stars in Andromeda VI
- Short Name:
- J/AJ/124/1464
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed Andromeda VI, a dwarf spheroidal galaxy companion to M31, for variable stars by using F450W and F555W observations obtained with the Hubble Space Telescope on 1999 October 25 and 1999 October 27 (WFPC2 instrument). A total of 118 variables were found, including 111 RR Lyrae stars, six anomalous Cepheids, and one variable that we were unable to classify. We find that the Andromeda VI anomalous Cepheids have properties consistent with those of anomalous Cepheids in other dwarf spheroidal galaxies. We revise the existing period-luminosity relations for these variables. Further, using these and other available data, we show that there is no clear difference between fundamental and first-overtone anomalous Cepheids in a period-amplitude diagram at shorter periods, unlike the RR Lyrae stars. For the Andromeda VI RR Lyrae stars, we find that they lie close to the Oosterhoff type I Galactic globular clusters in the period-amplitude diagram, although the mean period of the RRab stars, <P_ab_>=0.588days, is slightly longer than that of the typical Oosterhoff type I cluster. The mean V magnitude of the RR Lyrae stars in Andromeda VI is 25.29+/-0.03, resulting in a distance 815+/-25kpc on the Lee, Demarque, & Zinn (1990ApJ...350..155L) distance scale. This is consistent with the distance derived from the I magnitude of the tip of the red giant branch. Similarly, the properties of the RR Lyrae stars indicate a mean abundance for Andromeda VI that is consistent with that derived from the mean red giant branch color.
- ID:
- ivo://CDS.VizieR/J/A+A/503/651
- Title:
- Variable stars in a VLT/VIMOS field in Carina
- Short Name:
- J/A+A/503/651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched for variable stars in deep V-band images of a field towards the Galactic plane in Carina. The images were taken with VIMOS instrument at ESO VLT during 4 contiguous nights in April 2005. We detected 348 variables among 50897 stars in the magnitude range between V=15.4 and V=24.5mag. Upon detection, we classified the variables by direct eye inspection of their light curves. All variable objects but 9 OGLE transits in the field are new discoveries. We provide a complete catalog of all variables which includes eclipsing/ellipsoidal binaries, miscellaneous pulsators (mostly delta Scuti-type variables), stars with flares and other (irregular and likely long-period) variables. Only two of the stars in our sample are known to host planets. Our result give some implications for future large variability surveys.
1494. Variable stars in Cen A
- ID:
- ivo://CDS.VizieR/J/A+A/478/755
- Title:
- Variable stars in Cen A
- Short Name:
- J/A+A/478/755
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Difference imaging has proven to be a powerful technique for detecting and monitoring the variability of unresolved stellar sources in M 31. Using this technique in surveys of galaxies outside the Local Group could have many interesting applications. The goal of this paper is to test difference imaging photometry on Centaurus A, the nearest giant elliptical galaxy, at a distance of 4Mpc. We obtained deep photometric data with the Wide Field Imager at the ESO/MPG 2.2m at La Silla spread over almost two months. Applying the difference imaging photometry package DIFIMPHOT, we produced high-quality difference images and detected variable sources. The sensitivity of the current observational setup was determined through artificial residual tests. In the resulting high-quality difference images, we detect 271 variable stars. We find a difference flux detection limit corresponding to m_R_~=24.5. Based on a simple model of the halo of Centaurus A, we estimate that a ground-based microlensing survey would detect in the order of 4 microlensing events per year due to lenses in the halo. Conclusions: Difference imaging photometry works very well at the distance of Centaurus A and promises to be a useful tool for detecting and studying variable stars in galaxies outside the local group. For microlensing surveys, a higher sensitivity is needed than achieved here, which would be possible with a large ground-based telescope or space observatory with wide-field imaging capabilities.
- ID:
- ivo://CDS.VizieR/J/ApJS/194/27
- Title:
- Variable stars in Cygnus OB2
- Short Name:
- J/ApJS/194/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of photometrically variable stars discovered within two 21.3'x21.3' fields centered on the Cygnus OB2 association (Cyg OB2). There have hitherto been no deep optical variability studies of Cyg OB2, despite it being replete with early-type massive stars, likely due to the high and variable extinction (up to A_V_~20) that permeates much of the region. Here, we provide results of the first variability study with this combination of spatial coverage (~0.5deg) and photometric depth (R~21mag). We find 121 stars to be variable in both R and I bands, 115 of them newly discovered. Of the 121 variables, we identify 27 eclipsing binaries and eclipsing-binary candidates, 52 pulsating variables, and 20 potential Herbig Ae/Be stars. Confirming both the status and the cluster membership of the Herbig Ae/Be stars would address the uncertainty regarding the age and star formation history of Cyg OB2. We match our catalog to known variables and binaries in the region, Two Micron All Sky Survey near-IR data, and Chandra X-ray observations to find counterparts to new variables in other wavelengths.
- ID:
- ivo://CDS.VizieR/J/ApJ/674/L81
- Title:
- Variable stars in dwarf galaxy CVn I
- Short Name:
- J/ApJ/674/L81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 23 RR Lyrae stars and three possible anomalous Cepheids (ACs) among 84 candidate variables in the recently discovered Canes Venatici I (CVn I) dwarf spheroidal galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/295/101
- Title:
- Variable stars in field of NGC 7789
- Short Name:
- J/A+A/295/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1323
- Title:
- Variable stars in Fornax dSph. III.
- Short Name:
- J/ApJ/701/1323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new study of the variable star population in globular cluster 5 of the Fornax dSph, based on B and V time series photometry obtained with the MagIC camera of the 6.5m Magellan Clay telescope and complementary Hubble Space Telescope archive data. Light curves and accurate periodicities were obtained for 30 RR Lyrae stars and one SX Phoenicis variable. The RR Lyrae sample includes 15 fundamental-mode pulsators, 13 first-overtone pulsators, one candidate double-mode pulsator and one RR Lyrae star with uncertain type classification. The average and minimum periods of the ab-type RR Lyrae stars, <P_ab_>=0.590days, P_ab,min_=0.53297days and the position in the horizontal branch type-metallicity plane, indicate that the cluster has Oosterhoff-intermediate properties, basically confirming previous indications by Mackey & Gilmore, although with some differences both in the period and type classification of individual variables.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A128
- Title:
- Variable stars in globular clusters
- Short Name:
- J/A+A/588/A128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To obtain time-series photometry of the very crowded central regions of Galactic globular clusters. To obtain better angular resolution than has been previously achieved with conventional CCDs on ground-based telescopes. To complete, or improve, the census of the variable star population in those stellar systems. Images were taken using the Danish 1.54-m Telescope at the ESO observatory at La Silla in Chile. The telescope was equipped with an electron-multiplying CCD, and the short-exposure-time images obtained (ten images per second) were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). Photometry was performed via difference image analysis. Automatic detection of variable stars in the field was attempted. The light curves of 12541 stars in the cores of ten globular clusters were statistically analysed to automatically extract the variable stars. We obtained light curves for 31 previously known variable stars (3 long-period irregular, 2 semi-regular, 20 RR Lyrae, 1 SX Phoenicis, 3 cataclysmic variables, 1 W Ursae Majoris-type and 1 unclassified) and we discovered 30 new variables (16 long-period irregular, 7 semi-regular, 4 RR Lyrae, 1 SX Phoenicis and 2 unclassified).
- ID:
- ivo://CDS.VizieR/J/A+A/556/A20
- Title:
- Variable stars in globular NGC7492
- Short Name:
- J/A+A/556/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a photometric V,R,I CCD time-series analysis with a baseline of about eight years of the outer-halo globular cluster NGC 7492 with the aim of searching for new variables and using these (and the previously known variables) to determine the physical parameters of interest for the cluster (e.g. metallicity, absolute magnitude of the horizontal branch, distance, etc.). We used difference image analysis to extract precise light curves in the relatively crowded star field, especially towards the densely populated central region. Several different approaches were used for variability detection that recover the known variables and lead to new discoveries. We determined the physical parameters of the only RR0 star using a light-curve Fourier decomposition analysis. We found one new long-period variable and two SX Phe stars in the blue straggler region. We also present one candidate SX Phe star that requires follow-up observations.