- 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.
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- 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/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.
- ID:
- ivo://CDS.VizieR/J/AJ/141/137
- Title:
- Pittsburgh SDSS Mg II QSO catalog
- Short Name:
- J/AJ/141/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of intervening Mg II quasar absorption-line systems in the redshift interval 0.36<=z<=2.28. The catalog was built from Sloan Digital Sky Survey Data Release Four (SDSS DR4, Cat. II/267) quasar spectra. Currently, the catalog contains ~17000 measured Mg II doublets. We also present data on the ~44600 quasar spectra which were searched to construct the catalog, including redshift and magnitude information, continuum-normalized spectra, and corresponding arrays of redshift-dependent minimum rest equivalent widths detectable at our confidence threshold. The catalog is available online. A careful second search of 500 random spectra indicated that, for every 100 spectra searched, approximately one significant Mg II system was accidentally rejected. Current plans to expand the catalog beyond DR4 quasars are discussed. Many Mg II absorbers are known to be associated with galaxies. Therefore, the combination of large size and well understood statistics makes this catalog ideal for precision studies of the low-ionization and neutral gas regions associated with galaxies at low to moderate redshift. An analysis of the statistics of Mg II absorbers using this catalog will be presented in a subsequent paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/843/143
- Title:
- Polarimetry & photometry of GRB with RINGO2
- Short Name:
- J/ApJ/843/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of early-time (~10^2^-10^4^s) photometry and polarimetry of all gamma-ray burst (GRB) optical afterglows observed with the RINGO2 imaging polarimeter on the Liverpool Telescope. Of the 19 optical afterglows observed, the following nine were bright enough to perform photometry and attempt polarimetry: GRB100805A, GRB101112A, GRB110205A, GRB110726A, GRB120119A, GRB120308A, GRB120311A, GRB120326A, and GRB120327A. We present multiwavelength light curves for these 9 GRBs, together with estimates of their optical polarization degrees and/or limits. We carry out a thorough investigation of detection probabilities, instrumental properties, and systematics. Using two independent methods, we confirm previous reports of significant polarization in GRB 110205A and 120308A, and report the new detection of P=6_-2_^+3^% in GRB101112A. We discuss the results for the sample in the context of the reverse- and forward-shock afterglow scenario, and show that GRBs with detectable optical polarization at early time have clearly identifiable signatures of reverse-shock emission in their optical light curves. This supports the idea that GRB ejecta contain large-scale magnetic fields, and it highlights the importance of rapid-response polarimetry.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/2081
- Title:
- Praesepe members light curves
- Short Name:
- J/MNRAS/442/2081
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By using the dense coverage of the extrasolar planet survey project HATNet (Hungarian-made Automated Telescope Network), we Fourier analyse 381 high-probability members of the nearby open cluster Praesepe (Beehive/M44/NGC 2632). In addition to the detection of 10 variables (of delta Scuti and other types), we identify 180 rotational variables (including the two known planet hosts). This sample increases the number of known rotational variables in this cluster for spectral classes earlier than M by more than a factor of 3. These stars closely follow a colour/magnitude - period relation from early F to late K stars. We approximate this relation by polynomials for an easier reference to the rotational characteristics in different colours. The total (peak-to-peak) amplitudes of the large majority (94%) of these variables span the range of 0.005-0.04mag. The periods cover a range from 2.5 to 15d. These data strongly confirm that Praesepe and the Hyades have the same gyrochronological ages. Regarding the two planet hosts, Pr0211 (the one with the shorter orbital period) has a rotational period that is ~2d shorter than the one expected from the main rotational pattern in this cluster. This, together with other examples discussed in the paper, may hint that star-planet interaction via tidal dissipation can be significant in some cases in the rotational evolution of stars hosting hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/ApJ/842/83
- Title:
- Praesepe members rotational periods from K2 LCs
- Short Name:
- J/ApJ/842/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze K2 light curves for 794 low-mass (1>~M_*_>~0.1M_{sun}_) members of the ~650Myr old open cluster Praesepe and measure rotation periods (P_rot_) for 677 of these stars. We find that half of the rapidly rotating >~0.3M_{sun}_ stars are confirmed or candidate binary systems. The remaining >~0.3M_{sun}_ fast rotators have not been searched for companions, and are therefore not confirmed single stars. We previously found that nearly all rapidly rotating 0.3M_{sun}_ stars in the Hyades are binaries, but we require deeper binary searches in Praesepe to confirm whether binaries in these two co-eval clusters have different P_rot_ distributions. We also compare the observed P_rot_ distribution in Praesepe to that predicted by models of angular-momentum evolution. We do not observe the clear bimodal P_rot_ distribution predicted by Brown (2014ApJ...789..101B) for >0.5M_{sun}_ stars at the age of Praesepe, but 0.25-0.5M_{sun}_ stars do show stronger bimodality. In addition, we find that >60% of early M dwarfs in Praesepe rotate more slowly than predicted at 650Myr by Matt+ (2015ApJ...799L..23M), which suggests an increase in braking efficiency for these stars relative to solar-type stars and fully convective stars. The incompleteness of surveys for binaries in open clusters likely impacts our comparison with these models since the models only attempt to describe the evolution of isolated single stars.
- ID:
- ivo://CDS.VizieR/J/AJ/130/873
- Title:
- Properties of BQS objects in the SDSS DR3 area
- Short Name:
- J/AJ/130/873
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing it with imaging and spectroscopy from the Sloan Digital Sky Survey (SDSS).
- ID:
- ivo://CDS.VizieR/J/AJ/143/133
- Title:
- Properties of dwarf galaxies from the ALFALFA survey
- Short Name:
- J/AJ/143/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the global properties of the stellar and HI components of 229 low HI mass dwarf galaxies extracted from the ALFALFA survey ({alpha}.40; Haynes et al., 2011, Cat. J/AJ/142/170), including a complete sample of 176 galaxies with HI masses<10^7.7^M_{sun}_and HI line widths<80km/s. Sloan Digital Sky Survey (SDSS; Cat . II/294 superseded by Cat. V/139) data are combined with photometric properties derived from Galaxy Evolution Explorer (GALEX; GR5, Cat. II/312) to derive stellar masses (M_*_) and star formation rates (SFRs) by fitting their UV-optical spectral energy distributions (SEDs). In optical images, many of the ALFALFA dwarfs are faint and of low surface brightness; only 56% of those within the SDSS footprint have a counterpart in the SDSS spectroscopic survey. A large fraction of the dwarfs have high specific star formation rates (SSFRs), and estimates of their SFRs and M_*_ obtained by SED fitting are systematically smaller than ones derived via standard formulae assuming a constant SFR. The increased dispersion of the SSFR distribution at M_*_<~10^8^M_{sun}_ is driven by a set of dwarf galaxies that have low gas fractions and SSFRs; some of these are dE/dSphs in the Virgo Cluster. The imposition of an upper HI mass limit yields the selection of a sample with lower gas fractions for their M_*_ than found for the overall ALFALFA population. Many of the ALFALFA dwarfs, particularly the Virgo members, have HI depletion timescales shorter than a Hubble time. An examination of the dwarf galaxies within the full ALFALFA population in the context of global star formation (SF) laws is consistent with the general assumptions that gas-rich galaxies have lower SF efficiencies than do optically selected populations and that HI disks are more extended than stellar ones.
- ID:
- ivo://CDS.VizieR/J/AJ/143/31
- Title:
- Properties of fragile binary candidates in SDSS DR8
- Short Name:
- J/AJ/143/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 80 very wide fragile binary candidates (projected separations >10000AU) from the Sloan Digital Sky Survey Data Release Eight spectral archive. The pairs were selected based on proper motion, radial velocity, metallicity, and photometric parallax criteria. The angular separations of these pairs range from 3" to 250". The peak in the metallicity distribution of these pairs is about -0.5dex of solar metallicity. Space motions and reduced proper motion diagrams indicate that all these pairs are members of the disk. The chromospheric activity index S_HK_ of each component in 38 binary candidates having spectra of high signal-to-noise ratio and member stars of three open clusters (NGC 2420, M67, and NGC 6791) were measured. The S_HK_ versus color relation for these binary candidates is consistent with the trend seen in these open clusters. The ages implied by this relation suggest that fragile wide pairs can survive longer than 8Gyr.
