- ID:
- ivo://CDS.VizieR/J/ApJ/770/43
- Title:
- Spectroscopic [Fe/H] of Kepler stars
- Short Name:
- J/ApJ/770/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It has been shown that F, G, and early K dwarf hosts of Neptune-sized planets are not preferentially metal-rich. However, it is less clear whether the same holds for late K and M dwarf planet hosts. We report metallicities of Kepler targets and candidate transiting planet hosts with effective temperatures below 4500K. We use new metallicity calibrations to determine [Fe/H] from visible and near-infrared spectra. We find that the metallicity distribution of late K and M dwarfs monitored by Kepler is consistent with that of the solar neighborhood. Further, we show that hosts of Earth- to Neptune-sized planets have metallicities consistent with those lacking detected planets and rule out a previously claimed 0.2dex offset between the two distributions at 6{sigma} confidence. We also demonstrate that the metallicities of late K and M dwarfs hosting multiple detected planets are consistent with those lacking detected planets. Our results indicate that multiple terrestrial and Neptune-sized planets can form around late K and M dwarfs with metallicities as low as 0.25 solar. The presence of Neptune-sized planets orbiting such low-metallicity M dwarfs suggests that accreting planets collect most or all of the solids from the disk and that the potential cores of giant planets can readily form around M dwarfs. The paucity of giant planets around M dwarfs compared to solar-type stars must be due to relatively rapid disk evaporation or a slower rate of planet accretion, rather than insufficient solids to form a core.
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- ID:
- ivo://CDS.VizieR/J/ApJ/898/84
- Title:
- Spectroscopic follow-up of 100pc WDs in SDSS & Gaia
- Short Name:
- J/ApJ/898/84
- Date:
- 25 Oct 2021 07:21:33
- Publisher:
- CDS
- Description:
- We present follow-up spectroscopy of 711 white dwarfs within 100pc, and we present a detailed model atmosphere analysis of the 100pc white dwarf sample in the Sloan Digital Sky Survey footprint. Our spectroscopic follow-up is complete for 83% of the white dwarfs hotter than 6000K, where the atmospheric composition can be constrained reliably. We identify 1508 DA white dwarfs with pure hydrogen atmospheres. The DA mass distribution has an extremely narrow peak at 0.59M_{sun}_ and reveals a shoulder from relatively massive white dwarfs with M=0.7-0.9M_{sun}_. Comparing this distribution with binary population synthesis models, we find that the contribution from single stars that form through mergers cannot explain the overabundance of massive white dwarfs. In addition, the mass distribution of cool DAs shows a near absence of M>1M_{sun}_ white dwarfs. The pile-up of 0.7-0.9M_{sun}_ and the disappearance of M>1M_{sun}_ white dwarfs is consistent with the effects of core crystallization. Even though the evolutionary models predict the location of the pile-up correctly, the delay from the latent heat of crystallization by itself is insufficient to create a significant pile-up, and additional cooling delays from related effects like phase separation are necessary. We also discuss the population of infrared-faint (ultracool) white dwarfs and demonstrate for the first time the existence of a well-defined sequence in color and magnitude. Curiously, this sequence is connected to a region in the color-magnitude diagrams where the number of white dwarfs with a helium- dominated atmosphere is low. This suggests that the infrared-faint white dwarfs likely have mixed H/He atmospheres.
- ID:
- ivo://CDS.VizieR/J/ApJS/250/26
- Title:
- Spectroscopic follow-up of the QUBRICS quasars
- Short Name:
- J/ApJS/250/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the spectroscopic follow-up of the QUasars as BRIght beacons for Cosmology in the Southern Hemisphere (QUBRICS; Calderone+ 2019, J/ApJ/887/268) survey. The selection method is based on a machine-learning approach applied to photometric catalogs, covering an area of ~12400deg^2^ in the Southern Hemisphere. The spectroscopic observations started in 2018 and identified 55 new, high-redshift (z>=2.5), bright (i<=18) quasi-stellar objects (QSOs), with the catalog published in late 2019. Here we report the current status of the survey, bringing the total number of bright QSOs at z>=2.5 identified by QUBRICS to 224. The success rate of the QUBRICS selection method, in its most recent training, is estimated to be 68%. The predominant contaminant turns out to be lower-z QSOs at z<2.5. This survey provides a unique sample of bright QSOs at high z available for a number of cosmological investigations. In particular, carrying out the redshift drift measurements (Sandage Test) in the Southern Hemisphere, using the High Resolution Spectrograph at the 39m Extremely Large Telescope appears to be possible with less than 2500hr of observations spread over 30 targets in 25yr.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/19
- Title:
- Spectroscopic HK' index for 3 globular clusters
- Short Name:
- J/ApJS/216/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is increasing evidence for the presence of multiple red giant branches (RGBs) in the color-magnitude diagrams of massive globular clusters (GCs). In order to investigate the origin of this split on the RGB, we have performed new narrow-band Ca photometry and low-resolution spectroscopy for M22, NGC 1851, and NGC 288. We find significant differences (more than 4{sigma}) in calcium abundance from the spectroscopic HK' index for M22 and NGC 1851. We also find more than 8{sigma} differences in CN-band strength between the Ca-strong and Ca-weak subpopulations for these GCs. For NGC 288, however, a large difference is detected only in the CN strength. The calcium abundances of RGB stars in this GC are identical to within the errors. This is consistent with the conclusion from our new Ca photometry where the RGB splits are confirmed in M22 and NGC 1851, but not in NGC 288. We also find interesting differences in the CN-CH correlations among these GCs. While CN and CH are anti-correlated in NGC 288, they show a positive correlation in M22. NGC 1851, however, shows no difference in CH between the two groups of stars with different CN strengths. We suggest that all of these systematic differences would be best explained by how strongly Type II supernovae enrichment has contributed to the chemical evolution of these GCs.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/57
- Title:
- Spectroscopic HR diagram of OB stars in the SMC
- Short Name:
- J/ApJ/868/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive stellar atmosphere analysis of 329 O- and B-type stars in the Small Magellanic Cloud (SMC) from the RIOTS4 survey. Using spectroscopically derived effective temperature Teff and surface gravities, we find that classical Be stars appear misplaced to low Teff and high luminosity in the spectroscopic Hertzsprung-Russell diagram (sHRD). Together with the most luminous stars in our sample, the stellar masses derived from the sHRD for these objects are systematically larger than those obtained from the conventional Hertzsprung-Russell diagram. This suggests that the well-known, spectroscopic mass-discrepancy problem may be linked to the fact that both groups of stars have outer envelopes that are nearly gravitationally unbound. The non-emission-line stars in our sample mainly appear on the main sequence, allowing a first estimate of the terminal-age main sequence (TAMS) in the SMC, which matches the predicted TAMS between 12 and 40M_{sun}_ at SMC metallicity. We further find a large underabundance of stars above ~25M_{sun}_ near the zero-age main sequence, reminiscent of such earlier findings in the Milky Way and Large Magellanic Cloud.
- ID:
- ivo://CDS.VizieR/J/MNRAS/398/133
- Title:
- Spectroscopic indexes of BCGs
- Short Name:
- J/MNRAS/398/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is part of a series devoted to the study of the stellar populations in brightest cluster galaxies (BCGs), aimed at setting constraints on the formation and evolution of these objects. We have obtained high signal-to-noise ratio, long-slit spectra of 49 BCGs in the nearby Universe. Here, we derive single stellar population (SSP)-equivalent ages, metallicities and alpha-abundance ratios in the centres of the galaxies using the Lick system of absorption line indices.
- ID:
- ivo://CDS.VizieR/J/AJ/152/207
- Title:
- Spectroscopic Indicators in SeisMic Archive (SISMA)
- Short Name:
- J/AJ/152/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We created a large database of physical parameters and variability indicators by fully reducing and analyzing the large number of spectra taken to complement the asteroseismic observations of the COnvection, ROtation and planetary Transits (CoRoT) satellite. 7103 spectra of 261 stars obtained with the ESO echelle spectrograph HARPS have been stored in the VO-compliant database Spectroscopic Indicators in a SeisMic Archive (SISMA), along with the CoRoT photometric data of the 72 CoRoT asteroseismic targets. The remaining stars belong to the same variable classes of the CoRoT targets and were observed to better characterize the properties of such classes. Several useful variability indicators (mean line profiles, indices of differential rotation, activity and emission lines) together with vsini and radial-velocity measurements have been extracted from the spectra. The atmospheric parameters T_eff_,logg, and [Fe/H] have been computed following a homogeneous procedure. As a result, we fully characterize a sample of new and known variable stars by computing several spectroscopic indicators, also providing some cases of simultaneous photometry and spectroscopy.
- ID:
- ivo://CDS.VizieR/J/A+A/595/A10
- Title:
- Spectroscopic mapping of supernova remnant N49
- Short Name:
- J/A+A/595/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Physical conditions inside a supernova remnant can vary significantly between different positions. However, typical observational data of supernova remnants are integrated data or contemplate specific portions of the remnant. We study the spatial variation in the physical properties of the N49 supernova remnant based on a spectroscopic mapping of the whole nebula. Long-slit spectra were obtained with the slit (~4'x1.03") aligned along the east-west direction from 29 different positions spaced by 2" in declination. A total of 3248 1D spectra were extracted from sections of 2" of the 2D spectra. More than 60 emission lines in the range 3550{AA} to 8920{AA} were measured in these spectra. Maps of the fluxes and of intensity ratios of these emission lines were built with a spatial resolution of 2"x2".
- ID:
- ivo://CDS.VizieR/J/A+A/622/A110
- Title:
- Spectroscopic membership for NGC 3532
- Short Name:
- J/A+A/622/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 3532 is an extremely rich open cluster embedded in the Galactic disc, hitherto lacking a comprehensive, documented membership list. We provide membership probabilities from new radial velocity observations of solar-type and low-mass stars in NGC 3532, in part as a prelude to a subsequent study of stellar rotation in the cluster. Using extant optical and infra-red photometry we constructed a preliminary photometric membership catalogue, consisting of 2230 dwarf and turn-off stars. We selected 1060 of these for observation with the AAOmega spectrograph at the 3.9m Anglo-Australian Telescope and 391 stars for observations with the Hydra-South spectrograph at the 4m Victor Blanco Telescope, obtaining spectroscopic observations over a decade for 145 stars. We measured radial velocities for our targets through cross-correlation with model spectra and standard stars, and supplemented them with radial velocities for 433 additional stars from the literature. We also measured logg, Teff, and [Fe/H] from the AAOmega spectra. The radial velocity distribution emerging from the observations is centred at 5.43+/-0.04km/s and has a width (standard deviation) of 1.46km/s. Together with proper motions from Gaia DR2 we find 660 exclusive members, of which five are likely binary members. The members are distributed across the whole cluster sequence, from giant stars to M dwarfs, making NGC~3532 one of the richest Galactic open clusters known to date, on par with the Pleiades. From further spectroscopic analysis of 153 dwarf members we find the metallicity to be marginally sub-solar, with [Fe/H]=-0.07+/-0.10. We confirm the extremely low reddening of the cluster, E_B-V_=0.034+/-0.012mag, despite its location near the Galactic plane. Exploiting trigonometric parallax measurements from Gaia DR2 we find a distance of 484^+35^_-30_pc [(m-M)_0_=8.42+/-0.14mag]. Based on the membership we provide an empirical cluster sequence in multiple photometric passbands. A comparison of the photometry of the measured cluster members with several recent model isochrones enables us to confirm the 300Myr cluster age. However, all of the models evince departures from the cluster sequence in particular regions, especially in the lower mass range.
- ID:
- ivo://CDS.VizieR/J/ApJ/880/142
- Title:
- Spectroscopic members of COSMOS X-ray systems
- Short Name:
- J/ApJ/880/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate spectroscopic properties of galaxy systems identified based on deep X-ray observations in the Cosmic Evolution Survey (COSMOS) field. The COSMOS X-ray system catalog we use includes 180 X-ray systems to a limiting flux of 1.0x10^-15^erg/cm^2^/s, an order of magnitude deeper than the future e-ROSITA survey. We identify spectroscopic members of these X-ray systems based on the spectroscopic catalog constructed by compiling various spectroscopic surveys including 277 new measurements; 146 X-ray systems are spectroscopically identified groups with more than three spectroscopic members. We identify 2196 spectroscopic redshifts of member candidates in these X-ray systems. The X-ray luminosity (L_X_)-velocity dispersion ({sigma}_v_) scaling relation of the COSMOS X-ray systems is consistent with that of massive X-ray clusters. One of the distinctive features of the COSMOS survey is that it covers the X-ray luminosity range where poor groups overlap the range for extended emission associated with individual quiescent galaxies. We assess the challenges posed by the complex morphology of the distribution of systems with low X-ray luminosity, including groups and individual quiescent galaxies, in the L_x_-{sigma}_v_ plane.