- ID:
- ivo://CDS.VizieR/J/ApJ/868/70
- Title:
- Hot subdwarf stars from Gaia DR2 and LAMOST DR5
- Short Name:
- J/ApJ/868/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected 4593 hot subdwarf candidates from the Gaia DR2 Hertzsprung-Russell (HR) diagram. By combining the sample with Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) DR5, we identified 294 hot subdwarf stars, including 169 sdB, 63 sdOB, 31 He-sdOB, 22 sdO, 7 He-sdO, and 2 He-sdB stars. The atmospheric parameters (e.g., Teff, logg, log(nHe/nH)) are obtained by fitting the hydrogen (H) and helium (He) line profiles with synthetic spectra. Two distinct He sequences of hot subdwarf stars are clearly presented in the Teff-logg diagram. We found that the He-rich sequence consists of the bulk of sdB and sdOB stars, as well as all of the He-sdB, He-sdO, and He-sdOB stars in our samples, while all the stars in the He-weak sequence belong to the sdO spectral type, combined with a few sdB and sdOB stars. We demonstrated that the combination of Gaia DR2 and LAMOST DR5 allows one to uncover a huge number of new hot subdwarf stars in our Galaxy.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/138/606
- Title:
- Hot subdwarf stars in rejected PG catalog
- Short Name:
- J/AJ/138/606
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The hot subdwarf (sd) stars in the Palomar Green (PG) catalog of ultraviolet excess (UVX) objects play a key role in investigations of the frequency and types of binary companions and the distribution of orbital periods. These are important for establishing whether and by which channels the sd stars arise from interactions in close binary systems. It has been suggested that the list of PG sd stars is biased by the exclusion of many stars in binaries, whose spectra show the CaII K line in absorption. A total of 1125 objects that were photometrically selected as candidates were ultimately rejected from the final PG catalog using this K-line criterion. We study 88 of these "PG-Rejects" (PGRs), to assess whether there are significant numbers of unrecognized sd stars in binaries among the PGR objects.
- ID:
- ivo://CDS.VizieR/J/AJ/135/1350
- Title:
- Hot variable stars in NGC 330
- Short Name:
- J/AJ/135/1350
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a sample of 150 hot stars in NGC 330, a SMC cluster containing a high fraction of Be stars, we searched for photometric variables using OGLE II data. At least one third of all stars are variable, with 38 being periodic. We found 27 pulsators ({lambda} Eri variables), six eclipsing systems, two bursting sources, and several stars with unusual photometric behavior. Pulsations are present in ~30% of known Be stars, and they are long lived, lasting more than a decade. The strongest pulsators are associated with stars evolved from the main sequence.
- ID:
- ivo://CDS.VizieR/J/AJ/160/259
- Title:
- HPF RVs and TESS photometry of TOI-1266
- Short Name:
- J/AJ/160/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the validation of two planets orbiting the nearby (36pc) M2 dwarf TOI-1266 observed by the TESS mission. This system is one of a few M dwarf multiplanet systems with close-in planets where the inner planet is substantially larger than the outer planet. The inner planet is sub-Neptune-sized (R=2.46{+/-}0.08R{Earth}) with an orbital period of 10.9days, while the outer planet has a radius of 1.67_-0.11_^+0.09^R{Earth} and resides in the exoplanet radius valley-the transition region between rocky and gaseous planets. With an orbital period of 18.8days, the outer planet receives an insolation flux of 2.4 times that of Earth, similar to the insolation of Venus. Using precision near-infrared radial velocities with the Habitable-zone Planet Finder Spectrograph, we place upper mass limits of 15.9 and 6.4M{Earth} at 95% confidence for the inner and outer planet, respectively. A more precise mass constraint of both planets, achievable with current radial velocity instruments given the host star brightness (V=12.9, J=9.7), will yield further insights into the dominant processes sculpting the exoplanet radius valley.
- ID:
- ivo://CDS.VizieR/J/A+A/511/L7
- Title:
- HR 7355 differential BV light curves
- Short Name:
- J/A+A/511/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Strong meridional mixing induced by rapid rotation is one reason why all hot main-sequence stars are not chemically peculiar. However, the finding that the He-strong CP star HR 7355 is a rapid rotator complicates this concept. Our goal is to explain the observed behaviour of HR 7355 based on period analysis of all available photometry. Over two years, we acquired 114 new BV observations of HR 7355 at observatories in Arizona, U.S.A and Cape Town, South Africa. We performed period analyses of the new observations along with new analyses of 732 archival measurements from the Hipparcos and ASAS projects. We find that the light curves of HR 7355 in various filters are quite similar, with amplitudes 0.035(4), 0.036(4), and 0.038(3) mag in B, Hp, and V, respectively. The light curves are double-peaked, with unevenly deep minima. We substantially refine the rotational period to be P=0.5214410(4)d, indicating that HR 7355 is the most rapidly rotating CP star known. Our period analyses reveal a possible lengthening of the rotational period with (dP/dt)/P=2.4(8)x10^-6^yr^-1^. We conclude that the shape and amplitude of HR 7355 light curves are typical of magnetic He-strong CP stars, for which light variations are the result of photospheric spots on the surface of a rotating star. We hypothesise that the light variations are caused mainly by an uneven distribution of overabundant helium on the star's surface. We briefly describe and discuss the cause of the rapid rotational braking of the star.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A105
- Title:
- HR8752 evolving through the void
- Short Name:
- J/A+A/546/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The main paper on the hypergiant HR8752 evolving through the void combines observational data from various sources: new spectral data, new and already published (B-V), V data. it also describes a new three-dimensional chebychev interpolating code, and gives information on the temperature calibration for hypergiants, and adds some extra Tables on colour excess and historical context (cf. below). The electronic appendix contains a number of tables, too large for publishing in the paper. In the text and in the appendix, they are referred to as Table Axx, resp. Cxx. We note, however, that tables A1.1 to A1.6 in Section 2 of the main paper are here referred to as tables appena11 to appena16. The observational tables appena11 to appena16, appena2, appena3, appena4 all refer to Section 2 in the main paper, while tables appena5, appena6, appena7, appena8 are used in Section 3 of the main paper. The technical table appenc1 describes the three-dimensional chebychev interpolation method used in Section 2 of the main paper. The second technical table appenc2 describes the (hypergiant) temperature calibration and transformation codes between Mk, Teff, and (B-V) data, used in Section 3 of the main paper. Table appena9 discusses some measured colour excesses (Section 3.3 of the main paper). Table appena10 discusses the possibility of historical context (Section 5.11 of the main paper).
- ID:
- ivo://CDS.VizieR/J/A+A/368/225
- Title:
- HR 5341, HD 142070, HR 6967 & HR 8434 uvby phot.
- Short Name:
- J/A+A/368/225
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Differential Stroemgren uvby observations from the Four College Automated Photoelectric Telescope (FCAPT) are presented for the mCP stars HD 142070, HR 6967, and HR 8434 and the CP star HR 5341. The latter star is found to be constant. Improved periods were derived for HD 142070, 3.37189d, HR 6967, 3.91227d, and HR 8434, 1.43237d. Further observations of HD 142070 are needed to phase the magnetic data with the photometry, of HR 6967 to settle minor discrepancies between y and scaled Geneva V photometry, and of HR 8434 to resolve small discrepancies between two uvby photometric data sets.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A71
- Title:
- HRS galaxies Halpha kinematic survey
- Short Name:
- J/A+A/631/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new 2D high resolution Fabry-Perot spectroscopic observations of 152 star-forming galaxies which are part of the Herschel Reference Survey (HRS), a complete K-band selected, volume-limited sample of nearby galaxies, spanning a wide range in stellar mass and morphological type. Using improved data reduction techniques that provide adaptive binning based on Voronoi tessellation, using large field-of-view observations, we derive high spectral resolution (R>10,000) H{alpha} datacubes from which we compute H{alpha} maps and radial 2D velocity fields that are based on several thousand independent measurements. A robust method based on such fields allows us to accurately compute rotation curves and kinematical parameters, for which uncertainties are calculated using a method based on the power spectrum of the residual velocity fields. We check the consistency of the rotation curves by comparing our maximum rotational velocities to those derived from Hi data, and computing the i-band, NIR, stellar and baryonic Tully-Fisher relations. We use this set of kinematical data combined to those available at other frequencies to study for the first time the relation between the dynamical and the total baryonic mass (stars, atomic and molecular gas, metals and dust), and derive the baryonic and dynamical main sequence on a representative sample of the local universe.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A33
- Title:
- HRS sample stellar, dust, gas mass functions
- Short Name:
- J/A+A/617/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the results of the relationships between the K-band and stellar mass, far-infrared luminosities, star formation rate, dust and gas masses of nearby galaxies computing the bivariate K-band Luminosity Function (BLF) and bivariate K-band Mass Function (BMF) of the Herschel Reference Survey (HRS), a volume-limited sample with full wavelength coverage. We derive the BLFs and BMFs from the K-band and stellar mass, far-infrared luminosities, star formation rate, dust and gas masses cumulative distributions using a copula method which is outlined in detail. The use of the bivariate computed taking into account the upper limits allows us to derive on a more solid statistical ground the relationship between the observed physical quantities. The analysis shows that the behaviour of the morphological (optically selected) subsamples is quite different. A statistically meaningful result can be obtained over the whole HRS sample only from the relationship between the K-band and the stellar mass, while for the remaining physical quantities (dust and gas masses, far-IR luminosity and star formation rate), the analysis is distinct for late-type (LT) and early-type galaxies (ETG). However, the number of ETGs is small to perform a robust statistical analysis, and in most of the case results are discussed only for the LTG subsample. The Luminosity and Mass Functions (LFs, MFs) of LTGs are generally dependent on the K-band and the various dependencies are discussed in detail. We are able to derive the corresponding LFs and MFs and compare them with those computed with other samples. Our statistical analysis allows us to characterise the HRS, that, although non homogeneously selected and partially biased towards low IR luminosities, may be considered as representative of the local LT galaxy population.
- ID:
- ivo://CDS.VizieR/J/AJ/159/103
- Title:
- HSC search of SDSS and GAMA dwarf gal. mergers
- Short Name:
- J/AJ/159/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Like massive galaxies, dwarf galaxies are expected to undergo major mergers with other dwarfs. However, the end state of these mergers and the role that merging plays in regulating dwarf star formation are uncertain. Using imaging from the Hyper Suprime-Cam Subaru Strategic Program, we construct a sample of dwarf-dwarf mergers and examine the star formation and host properties of the merging systems. These galaxies are selected via an automated detection algorithm from a sample of 6875 spectroscopically selected isolated dwarf galaxies at z<0.12 and log(M_*_/M_{sun}_)<9.6 from the Galaxy and Mass Assembly and Sloan Digital Sky Survey spectroscopic campaigns. We find a total tidal feature detection fraction of 3.29% (6.1% when considering only galaxies at z<0.05). The tidal feature detection fraction rises strongly as a function of star formation activity; 15%-20% of galaxies with extremely high H{alpha} equivalent width (EW_H{alpha}_>250{AA}) show signs of tidal debris. Galaxies that host tidal debris are also systematically bluer than the average galaxy at fixed stellar mass. These findings extend the observed dwarf-dwarf merger sequence with a significant sample of dwarf galaxies, indicating that star formation triggered in mergers between dwarf galaxies continues after coalescence.