- ID:
- ivo://CDS.VizieR/J/ApJS/185/451
- Title:
- PMS stars in the Cepheus flare region
- Short Name:
- J/ApJS/185/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of optical spectroscopic and BVR_C_I_C_ photometric observations of 77 pre-main-sequence (PMS) stars in the Cepheus flare region. A total of 64 of these are newly confirmed PMS stars, originally selected from various published candidate lists. We estimate effective temperatures and luminosities for the PMS stars, and comparing the results with PMS evolutionary models, we estimate stellar masses of 0.2-2.4M_{sun}_ and stellar ages of 0.1-15Myr. Among the PMS stars, we identify 15 visual binaries with separations of 2-10". From archival IRAS, Two Micron All Sky Survey, and Spitzer data, we construct their spectral energy distributions (SEDs) and classify 5% of the stars as Class I, 10% as Flat SED, 60% as Class II, and 3% as Class III young stellar objects. We identify 12 classical T Tauri stars and two weak-line T Tauri stars as members of NGC 7023, with a mean age of 1.6Myr. The 13 PMS stars associated with L1228 belong to three small aggregates: RNO 129, L1228A, and L1228S. The age distribution of the 17 PMS stars associated with L1251 suggests that star formation has propagated with the expansion of the Cepheus flare shell. We detect sparse aggregates of ~6-7Myr old PMS stars around the dark clouds L1177 and L1219, at a distance of ~400pc. Three T Tauri stars appear to be associated with the Herbig Ae star SV Cep at a distance of 600pc. Our results confirm that the molecular complex in the Cepheus flare region contains clouds of various distances and star-forming histories.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/862/2
- Title:
- Post-starburst galaxy ages from SDSS
- Short Name:
- J/ApJ/862/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed modeling of the recent star formation histories (SFHs) of post-starburst (or "E+A") galaxies is impeded by the degeneracy between the time elapsed since the starburst ended (post-burst age), the fraction of stellar mass produced in the burst (burst strength), and the burst duration. To resolve this issue, we combine GALEX ultraviolet photometry, SDSS photometry and spectra, and new stellar population synthesis models to fit the SFHs of 532 post-starburst galaxies. In addition to an old stellar population and a recent starburst, 48% of the galaxies are best fit with a second recent burst. Lower stellar mass galaxies (logM*/M_{sun}_<10.5) are more likely to experience two recent bursts, and the fraction of their young stellar mass is more strongly anticorrelated with their total stellar mass. Applying our methodology to other, younger post-starburst samples, we identify likely progenitors to our sample and examine the evolutionary trends of molecular gas and dust content with post-burst age. We discover a significant (4{sigma}) decline, with a 117-230Myr characteristic depletion time, in the molecular gas to stellar mass fraction with the post-burst age. The implied rapid gas depletion rate of 2-150M_{sun}_/yr cannot be due to current star formation, given the upper limits on the current star formation rates in these post- starbursts. Nor are stellar winds or supernova feedback likely to explain this decline. Instead, the decline points to the expulsion or destruction of molecular gas in outflows, a possible smoking gun for active galactic nucleus feedback.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A144
- Title:
- Proper motions of young stars in Chamaeleon
- Short Name:
- J/A+A/556/A144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for new candidate members of the Chamaeleon I and II star forming regions based on proper motions and multiwavelength photometry. Kinematic candidate members are initially selected in an area of 3 degrees around each cloud on the basis of proper motions and colours using the UCAC4 catalogue. The SEDs of the objects are constructed using photometry retrieved from the Virtual Observatory and other resources, and fitted to models of stellar photospheres in order to derive effective temperatures, gravity values and luminosities. Masses and ages are estimated by comparison with theoretical evolutionary tracks in a Hertzprung-Russell diagram. Objects with ages <=20Myr are selected as probable members of the moving groups. The properties of our candidates are compared with those of the previously known members of the clouds.
- ID:
- ivo://CDS.VizieR/J/AJ/155/149
- Title:
- Properties of co-moving stars observed by Gaia
- Short Name:
- J/AJ/155/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have estimated fundamental parameters for a sample of co-moving stars observed by Gaia and identified by Oh et al (2017, J/AJ/153/257). We matched the Gaia observations to the 2MASS and Wide-Field Infrared Survey Explorer catalogs and fit MIST isochrones to the data, deriving estimates of the mass, radius, [Fe/H], age, distance, and extinction to 9754 stars in the original sample of 10606 stars. We verify these estimates by comparing our new results to previous analyses of nearby stars, examining fiducial cluster properties, and estimating the power-law slope of the local present-day mass function. A comparison to previous studies suggests that our mass estimates are robust, while metallicity and age estimates are increasingly uncertain. We use our calculated masses to examine the properties of binaries in the sample and show that separation of the pairs dominates the observed binding energies and expected lifetimes.
- ID:
- ivo://CDS.VizieR/J/other/Nat/586.528
- Title:
- Properties of exoplanet host stars
- Short Name:
- J/other/Nat/586.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Planet formation is generally described in terms of a system containing the host star and a protoplanetary disk, of which the internal properties (for example, mass and metallicity) determine the properties of the resulting planetary system. However, (proto)planetary systems are predicted and observed to be affected by the spatially clustered stellar formation environment, through either dynamical star-star interactions or external photoevaporation by nearby massive stars. It is challenging to quantify how the architecture of planetary sysems is affected by these environmental processes, because stellar groups spatially disperse within less than a billion years, well below the ages of most known exoplanets. Here we identify old, co-moving stellar groups around exoplanet host stars in the astrometric data from the Gaia satellite and demonstrate that the architecture of planetary systems exhibits a strong dependence on local stellar clustering in position-velocity phase space. After controlling for host stellar age, mass, metallicity and distance from the star, we obtain highly significant differences (with p values of 10^-5^ to 10^-2^) in planetary system properties between phase space overdensities (composed of a greater number of co-moving stars than unstructured space) and the field. The median semi-major axis and orbital period of planets in phase space overdensities are 0.087 astronomical units and 9.6 days, respectively, compared to 0.81 astronomical units and 154 days, respectively, for planets around field stars. 'Hot Jupiters' (massive, short-period exoplanets) predominantly exist in stellar phase space overdensities, strongly suggesting that their extreme orbits originate from environmental perturbations rather than internal migration or planet-planet scattering. Our findings reveal that stellar clustering is a key factor setting the architectures of planetary systems.
- ID:
- ivo://CDS.VizieR/J/PASJ/59/335
- Title:
- Properties of 160 F-K disk dwarfs/subgiants
- Short Name:
- J/PASJ/59/335
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The properties of 160 F, G, and K disk dwarfs/subgiants (including 27 planet-host stars) mostly within -0.6<~[Fe/H]<~+0.4, the Okayama Astrophysical Observatory spectrum collection of which had been made open to the public recently, were extensively investigated with particular attention to determining (1) the mass and the age with the help of theoretical stellar evolution calculations, (2) the kinematic parameters of orbital motions in the Galaxy, and (3) the abundances of 15 elements (Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, and Zn) by analyzing the spectra in this database. The resulting characteristics are discussed in terms of several relevant topics of interest, such as a validity check for assuming LTE, the [X/Fe] vs. [Fe/H] diagram containing information on the chemical evolution of the Galactic disk, the age-metallicity-kinematics relation, and the difference/similarity between stars with and without planets.
- ID:
- ivo://CDS.VizieR/J/MNRAS/436/1883
- Title:
- Properties of KOI host stars
- Short Name:
- J/MNRAS/436/1883
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report rotation periods, variability characteristics, gyrochronological ages for ~950 of the Kepler Object of Interest host stars. We find a wide dispersion in the amplitude of the photometric variability as a function of rotation, likely indicating differences in the spot distribution among stars. We use these rotation periods in combination with published spectroscopic measurements of vsini and stellar parameters to derive the stellar inclination in the line of sight, and find a number of systems with possible spin-orbit misalignment. We additionally find several systems with close-in planet candidates whose stellar rotation periods are equal to or twice the planetary orbital period, indicative of possible tidal interactions between these planets and their parent stars. If these systems survive validation to become confirmed planets, they will provide important clues to the evolutionary history of these systems.
- ID:
- ivo://CDS.VizieR/J/AJ/156/213
- Title:
- Properties of N2K stars & new gas giant companions
- Short Name:
- J/AJ/156/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The N2K planet search program was designed to exploit the planet-metallicity correlation by searching for gas giant planets orbiting metal-rich stars. Here, we present the radial velocity measurements for 378 N2K target stars that were observed with the HIRES spectrograph at Keck Observatory between 2004 and 2017. With this data set, we announce the discovery of six new gas giant exoplanets: a double-planet system orbiting HD 148164 (Msini of 1.23 and 5.16 M_JUP_) and single planet detections around HD 55696 (Msini=3.87 M_JUP_), HD 98736 (Msini=2.33 M_JUP_), HD 203473 (Msini=7.8 M_JUP_), and HD 211810 (Msini=0.67 M_JUP_). These gas giant companions have orbital semimajor axes between 1.0 and 6.2 au and eccentricities ranging from 0.13 to 0.71. We also report evidence for three gravitationally bound companions with Msini between 20 and 30 M_JUP_, placing them in the mass range of brown dwarfs, around HD 148284, HD 214823, and HD 217850, and four low-mass stellar companions orbiting HD 3404, HD 24505, HD 98630, and HD 103459. In addition, we present updated orbital parameters for 42 previously announced planets. We also report a nondetection of the putative companion HD 73256 b. Finally, we highlight the most promising candidates for direct imaging and astrometric detection, and we find that many hot Jupiters from our sample could be detectable by state-of-the-art telescopes such as Gaia.
- ID:
- ivo://CDS.VizieR/J/AJ/155/44
- Title:
- Properties of PMS stars in young cluster Berkeley 59
- Short Name:
- J/AJ/155/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Berkeley 59 is a nearby (~1 kpc) young cluster associated with the Sh2-171 H II region. We present deep optical observations of the central ~2.5x2.5 pc^2^ area of the cluster, obtained with the 3.58 m Telescopio Nazionale Galileo. The V/(V-I) color-magnitude diagram manifests a clear pre-main-sequence (PMS) population down to ~0.2 M_{sun}_. Using the near-infrared and optical colors of the low-mass PMS members, we derive a global extinction of A_V_=4 mag and a mean age of ~1.8 Myr, respectively, for the cluster. We constructed the initial mass function and found that its global slopes in the mass ranges of 0.2-28 M_{sun}_ and 0.2-1.5 M_{sun}_ are -1.33 and -1.23, respectively, in good agreement with the Salpeter value in the solar neighborhood. We looked for the radial variation of the mass function and found that the slope is flatter in the inner region than in the outer region, indicating mass segregation. The dynamical status of the cluster suggests that the mass segregation is likely primordial. The age distribution of the PMS sources reveals that the younger sources appear to concentrate close to the inner region compared to the outer region of the cluster, a phenomenon possibly linked to the time evolution of star-forming clouds. Within the observed area, we derive a total mass of ~10^3^ M_{sun}_ for the cluster. Comparing the properties of Berkeley 59 with other young clusters, we suggest it resembles more closely the Trapezium cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A26
- Title:
- Properties of the Population II star HD 140283
- Short Name:
- J/A+A/575/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Metal-poor halo stars are important astrophysical laboratories that allow us to unravel details about many aspects of astrophysics, including the chemical conditions at the formation of our Galaxy, understanding the processes of diffusion in stellar interiors, and determining precise effective temperatures and calibration of colour-effective temperature relations. To address any of these issues the fundamental properties of the stars must first be determined. HD 140283 is the closest and brightest metal-poor Population II halo star (distance = 58pc and V=7.21), an ideal target that allows us to approach these questions, and one of a list of 34 benchmark stars defined for Gaia astrophysical parameter calibration. In the framework of characterizing these benchmark stars, we determined the fundamental properties of HD 140283 (radius, mass, age, and effective temperature) by obtaining new interferometric and spectroscopic measurements and combining them with photometry from the literature. The interferometric measurements were obtained using the visible interferometer VEGA on the CHARA array and we determined a 1D limb-darkened angular diameter of {theta}_1D_=0.353+/-0.013-milliarcsec.
