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- ID:
- ivo://CDS.VizieR/J/ApJ/627/579
- Title:
- Photometry of variables in NGC 3370
- Short Name:
- J/ApJ/627/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report observations of two nearby Type Ia supernovae (SNe Ia) for which observations of Cepheid variables in the host galaxies have been obtained with the Hubble Space Telescope: SN 1994ae in NGC 3370 and SN 1998aq in NGC 3982. For NCG 3370, we used the Advanced Camera for Surveys to observe 64 Cepheids that yield a distance of 29 Mpc, the farthest direct measurement of Cepheids.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/19
- Title:
- Photometry of variable star candidates in M31
- Short Name:
- J/ApJ/743/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry in B, V (down to V~26mag) is presented for two 23'x23' fields of the Andromeda galaxy (M31) that were observed with the blue channel camera of the Large Binocular Telescope during the Science Demonstration Time. Each field covers an area of about 5.1x5.1kpc^2^ at the distance of M31 ({mu}_M31_~24.4mag), sampling, respectively, a northeast region close to the M31 giant stream (field S2) and an eastern portion of the halo in the direction of the galaxy minor axis (field H1). The stream field spans a region that includes Andromeda's disk and giant stream, and this is reflected in the complexity of the color-magnitude diagram of the field. One corner of the halo field also includes a portion of the giant stream. Even though these demonstration time data were obtained under non-optimal observing conditions, the B photometry, which was acquired in time-series mode, allowed us to identify 274 variable stars (among which 96 are bona fide and 31 are candidate RR Lyrae stars, 71 are Cepheids, and 16 are binary systems) by applying the image subtraction technique to the selected portions of the observed fields. Differential flux light curves were obtained for the vast majority of these variables. Our sample mainly includes pulsating stars that populate the instability strip from the Classical Cepheids down to the RR Lyrae stars, thus tracing the different stellar generations in these regions of M31 down to the horizontal branch of the oldest (t~10Gyr) component.
- ID:
- ivo://CDS.VizieR/J/AJ/149/50
- Title:
- Photometry of 105 variable stars from CSTAR
- Short Name:
- J/AJ/149/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Chinese Small Telescope ARray carried out high-cadence time-series observations of 27 square degrees centered on the South Celestial Pole during the Antarctic winter seasons of 2008-2010. Aperture photometry of the 2008 and 2010 i-band images resulted in the discovery of over 200 variable stars. Yearly servicing left the array defocused for the 2009 winter season, during which the system also suffered from intermittent frosting and power failures. Despite these technical issues, nearly 800000 useful images were obtained using g, r, and clear filters. We developed a combination of difference imaging and aperture photometry to compensate for the highly crowded, blended, and defocused frames. We present details of this approach, which may be useful for the analysis of time-series data from other small-aperture telescopes regardless of their image quality. Using this approach, we were able to recover 68 previously known variables and detected variability in 37 additional objects. We also have determined the observing statistics for Dome A during the 2009 winter season; we find the extinction due to clouds to be less than 0.1 and 0.4mag for 40% and 63% of the dark time, respectively.
- ID:
- ivo://CDS.VizieR/J/AJ/146/139
- Title:
- 2010 photometry of variable stars from Dome A
- Short Name:
- J/AJ/146/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a season of observations with the Chinese Small Telescope ARray, obtained over 183 days of the 2010 Antarctic winter. We carried out high-cadence time-series aperture photometry of 9125 stars with i{<~}15.3mag located in a 23deg^2^ region centered on the south celestial pole. We identified 188 variable stars, including 67 new objects relative to our 2008 observations, thanks to broader synoptic coverage, a deeper magnitude limit, and a larger field of view. We used the photometric data set to derive site statistics from Dome A. Based on two years of observations, we find that extinction due to clouds at this site is less than 0.1 and 0.4mag during 45% and 75% of the dark time, respectively.
- ID:
- ivo://CDS.VizieR/J/AJ/117/286
- Title:
- Photometry of variable stars in NGC 7006
- Short Name:
- J/AJ/117/286
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- B and V CCD photometry from 1984 through 1994 is presented for 50 RR Lyrae stars and two red variable stars in the globular cluster NGC 7006. New determinations of pulsation periods and period change rates are given and used to plot B light curves. The new photometry is combined with previously published photometry obtained from photographic plates taken in the 1930s, the 1950s and 1984 and used to derive O - C diagrams and new period change rates. V light curves based on the CCD data are also displayed, and colors derived from mean values of B and V are given. Period-amplitude diagrams and the color-magnitude diagram for the variables are shown.
- ID:
- ivo://CDS.VizieR/J/A+A/327/145
- Title:
- Photopolarimetric activity of RR Tauri
- Short Name:
- J/A+A/327/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of coordinated Crimea-Dodaira simultaneous multi-bands photometric and polarimetric observations of the classical Herbig Ae/Be star RR Tau which cover fully the observed interval of its brightness changes are presented. Within the observed interval of its light variations the linear polarization of RR Tau anti-correlates with its brightness changes.
- ID:
- ivo://CDS.VizieR/J/AZh/77/420
- Title:
- Photopolarimetric activity of SV Cep
- Short Name:
- J/AZh/77/420
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of the eleven-years (1987-98) photopolarimetric patrol observations of Herbig Ae star SV Cep are presented. Only one deep brightness minimum of star were observed during this time interval. The decrease of the SV Cep brightness during this minimum was accompanied by increase of its linear polarization. The similar behaviour of linear polarization with the brightness changes was found earlier in other young stars with the non-periodic Algol-type minima. The most probable interpretation of this phenomenon is based on the model in which the source of intrinsic linear polarization is the scattered radiation of circumstellar disk-like dust envelope (probably the proto-planetary disk). The deposition of this source increases during the brightness minima when the direct (non-polarized) stellar radiation are absorbed in the CS dust clouds intersected the line-of-sight.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A82
- Title:
- Physical parameters of classical Cepheids
- Short Name:
- J/A+A/616/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We gathered more than 1130 high-resolution optical spectra for more than 250 Galactic classical Cepheids. The spectra were collected with different optical spectrographs: UVES at VLT, HARPS at 3.6m, FEROS at 2.2m MPG/ESO, and STELLA. To improve the effective temperature estimates, we present more than 150 new line depth ratio (LDR) calibrations that together with similar calibrations already available in the literature allowed us to cover a broad range in wavelength (between 5348 and 8427 angstrom) and in effective temperatures (between 3500 and 7700K). This means the unique opportunity to cover both the hottest and coolest phases along the Cepheid pulsation cycle and to limit the intrinsic error on individual measurements at the level of ~100K. Thanks to the high signal-to-noise ratio of individual spectra we identified and measured hundreds of neutral and ionized lines of heavy elements, and in turn, have the opportunity to trace the variation of both surface gravity and microturbulent velocity along the pulsation cycle. The accuracy of the physical parameters and the number of FeI (more than one hundred) and FeII (more than ten) lines measured allowed us to estimate mean iron abundances with a precision better than 0.1dex. Here we focus on 14 calibrating Cepheids for which the current spectra cover either the entire or a significant portion of the pulsation cycle. The current estimates of the variation of the physical parameters along the pulsation cycle and of the iron abundances agree quite well with similar estimates available in the literature. Independent homogeneous estimates of both physical parameters and metal abundances based on different approaches that can constrain possible systematics are highly encouraged.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A141
- Title:
- Physical properties of AM CVn stars
- Short Name:
- J/A+A/620/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AM CVn binaries are hydrogen deficient compact binaries with an orbital period in the 5-65min range and are predicted to be strong sources of persistent gravitational wave radiation. Using Gaia, Data Release 2, we present the parallaxes and proper motions of 41 out of the 56 known systems. Compared to the parallax determined using the HST, Fine Guidance Sensor we find that the archetype star, AM CVn, is significantly closer than previously thought. This resolves the high luminosity and mass accretion rate which models had difficulty in explaining. Using Pan-STARRS1 data we determine the absolute magnitude of the AM CVn stars. There is some evidence that donor stars have a higher mass and radius than expected for white dwarfs or that the donors are not white dwarfs. Using the distances to the known AM CVn stars we find strong evidence that a large population of AM CVn stars has yet to be discovered. As this value sets the background to the gravitational wave signal of LISA, this is of wide interest. We determine the mass transfer rate for 15 AM CVn stars and find that the majority has a rate significantly greater than expected from standard models. This is further evidence that the donor star has a greater size than expected.
