- ID:
- ivo://CDS.VizieR/J/ApJ/818/202
- Title:
- Hot subdwarf stars in LAMOST DR1
- Short Name:
- J/ApJ/818/202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 166 spectroscopically identified hot subdwarf stars from LAMOST DR1, 44 of which show the characteristics of cool companions in their optical spectra. Atmospheric parameters of 122 subdwarf stars with non-composite spectra were measured by fitting the profiles of hydrogen (H) and helium (He) lines with synthetic spectra from non-LTE model atmospheres. A unique property of our sample is that it covers a large range in apparent magnitude and galactic latitude, therefore it contains a mix of stars from different populations and galactic environments.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/871/63
- Title:
- How to constrain your M dwarf. II. Nearby binaries
- Short Name:
- J/ApJ/871/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass-luminosity relation for late-type stars has long been a critical tool for estimating stellar masses. However, there is growing need for both a higher-precision relation and a better understanding of systematic effects (e.g., metallicity). Here we present an empirical relationship between M_Ks_ and M_*_ spanning 0.075M_{sun}_<M_*_<0.70M_{sun}_. The relation is derived from 62 nearby binaries, whose orbits we determine using a combination of near infra-red (Keck/NIRC2) imaging, archival adaptive optics data, and literature astrometry. From their orbital parameters, we determine the total mass of each system, with a precision better than 1% in the best cases. We use these total masses, in combination with resolved Ks magnitudes and system parallaxes, to calibrate the M_Ks_-M_*_ relation. The resulting posteriors can be used to determine masses of single stars with a precision of 2%-3%, which we confirm by testing the relation on stars with individual dynamical masses from the literature. The precision is limited by scatter around the best-fit relation beyond measured M_*_ uncertainties, perhaps driven by intrinsic variation in the M_Ks_-M_*_ relation or underestimated uncertainties in the input parallaxes. We find that the effect of [Fe/H] on the M_Ks_-M_*_ relation is likely negligible for metallicities in the solar neighborhood (0.0%{+/-}2.2% change in mass per dex change in [Fe/H]). This weak effect is consistent with predictions from the Dartmouth Stellar Evolution Database, but inconsistent with those from modules for experiments in stellar astrophysics (MESA) Isochrones and Stellar Tracks (MIST) (at 5{sigma}). A sample of binaries with a wider range of abundances will be required to discern the importance of metallicity in extreme populations (e.g., in the Galactic halo or thick disk).
- 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/587/A57
- Title:
- HR 8799e and HR 8799d spectra
- Short Name:
- J/A+A/587/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The planetary system discovered around the young A-type HR 8799 provides a unique laboratory to: a) test planet formation theories; b) probe the diversity of system architectures at these separations, and c) perform comparative (exo)planetology. We present and exploit new near-infrared images and integral-field spectra of the four gas giants surrounding HR 8799 obtained with SPHERE, the new planet finder instrument at the Very Large Telescope, during the commissioning and science verification phase of the instrument (July-December 2014). With these new data, we contribute to completing the spectral energy distribution (SED) of these bodies in the 1.0-2.5um range. We also provide new astrometric data, in particular for planet e, to further constrain the orbits. We used the infrared dual-band imager and spectrograph (IRDIS) subsystem to obtain pupil-stabilized, dual-band H2H3 (1.593um, 1.667um), K1K2 (2.110um, 2.251um), and broadband J (1.245um) images of the four planets. IRDIS was operated in parallel with the integral field spectrograph (IFS) of SPHERE to collect low-resolution (R~30), near-infrared (0.94-1.64um) spectra of the two innermost planets HR 8799 d and e. The data were reduced with dedicated algorithms, such as the Karhunen-Loeve image projection (KLIP), to reveal the planets. We used the so-called negative planets injection technique to extract their photometry, spectra, and measure their positions. We illustrate the astrometric performance of SPHERE through sample orbital fits compatible with SPHERE and literature data.
1105. HR8799e K-band spectrum
- ID:
- ivo://CDS.VizieR/J/A+A/623/L11
- Title:
- HR8799e K-band spectrum
- Short Name:
- J/A+A/623/L11
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- To date, infrared interferometry at best achieved contrast ratios of a few times 10^-4^ on bright targets. GRAVITY, with its dual-field mode, is now capable of high contrast observations, enabling the direct observation of exoplanets. We demonstrate the technique on HR 8799, a young planetary system composed of four known giant exoplanets. We used the GRAVITY fringe tracker to lock the fringes on the central star, and integrated off-axis on the HR 8799 e planet situated at 390mas from the star. Data reduction included post-processing to remove the flux leaking from the central star and to extract the coherent flux of the planet. The inferred K band spectrum of the planet has a spectral resolution of 500. We also derive the astrometric position of the planet relative to the star with a precision on the order of 100{mu}as. The GRAVITY astrometric measurement disfavors perfectly coplanar stable orbital solutions. A small adjustment of a few degrees to the orbital inclination of HR 8799 e can resolve the tension, implying that the orbits are close to, but not strictly coplanar. The spectrum, with a signal-to-noise ratio of ~5 per spectral channel, is compatible with a late-type L brown dwarf. Using Exo-REM synthetic spectra, we derive a temperature of 1150+/-50K and a surface gravity of 10^4.3+/-0.3^cm.s^2^. This corresponds to a radius of 1.17_-0.11_^+0.13^R_Jup_ and a mass of 10_-4_^+7^M_Jup_, which is an independent confirmation of mass estimates from evolutionary models. Our results demonstrate the power of interferometry for the direct detection and spectroscopic study of exoplanets at close angular separations from their stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/795/58
- Title:
- 1H 0323+342 rest frame optical spectrum with GHAO
- Short Name:
- J/ApJ/795/58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and near-infrared (NIR) imaging data of the radio-loud, narrow-line Seyfert 1 galaxy 1H 0323+342, which shows intense and variable gamma-ray activity discovered by the Fermi satellite with the Large Area Telescope. Near-infrared and optical images are used to investigate the structural properties of the host galaxy of 1H 0323+342; this together with optical spectroscopy allows us to examine its black hole mass. Based on two-dimensional (2D) multiwavelength surface-brightness modeling, we find that statistically, the best model fit is a combination of a nuclear component and a Sersic profile (n~2.8). However, the presence of a disk component (with a small bulge n~1.2) also remains a possibility and cannot be ruled out with the present data. Although at first glance a spiral-arm-like structure is revealed in our images, a 2D Fourier analysis of the imagery suggests that this structure corresponds to an asymmetric ring, likely associated with a recent violent dynamical interaction. We discuss our results in the context of relativistic jet production and galaxy evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/695/1527
- Title:
- HR 8257: orbit and basic properties
- Short Name:
- J/ApJ/695/1527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used interferometric and spectroscopic observations of HR 8257 to determine a three-dimensional orbit of the system. The orbit has a period of 12.21345 days and an eccentricity of 0.2895. The masses of the F0 and F2 dwarf components are 1.56 and 1.38M_{sun}_, respectively, with fractional errors of 1.4%. Our orbital parallax of 13.632+/-0.095mas, corresponding to a distance of 73.4+/-0.6pc, differs from the Hipparcos result by just 2% and has a significantly smaller uncertainty. From our spectroscopic observations and spectral energy distribution modeling we determine the component effective temperatures and luminosities to be T_eff_(A)=7030+/-200K and T_eff_(B)=6560+/-200K and L_A_=9.4+/-0.3L_{sun}_ and L_B_=4.7+/-0.2L_{sun}_. The primary rotates pseudosynchronously, while the secondary is not far from its pseudosynchronous rotational velocity. Although both early-F stars are slowly rotating, neither component of this close binary is an Am star. A comparison with evolutionary tracks indicates that the stars are slightly metal poor, and although the components have evolved away from the zero-age main sequence, they are both still dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A104
- Title:
- HRS gal. nuclear vs. integrated spectroscopy
- Short Name:
- J/A+A/615/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The determination of the relative frequency of active galactic nuclei (AGN) versus other spectral classes, for example, HII region-like (HII), transition objects (TRAN), passive (PAS), and retired (RET), in a complete set of galaxies in the local Universe is of primary importance to discriminate the source of ionization in the nuclear region of galaxies (e.g., supermassive black holes vs. young and old stars). Here we aim to provide a spectroscopic characterization of the nuclei of galaxies belonging to the Herschel Reference Survey (HRS), a volume and magnitude limited sample representative of the local Universe, which has become a benchmark for local and high- z studies, for semianalytical models and cosmological simulations. The comparison between the nuclear spectral classification and the one determined on the global galactic scale provides information about how galaxy properties change from the nuclear to the outer regions. Moreover, the extrapolation of the global star formation (SF) properties from the SDSS fiber spectroscopy compared to the one computed by H{alpha} photometry can be useful for testing the method based on aperture correction for determining the global star formation rate for local galaxies. By collecting the existing nuclear spectroscopy available from the literature, complemented with new observations obtained using the Loiano 1.52m telescope, we analyze the 322 nuclear spectra of HRS galaxies; their integrated spectroscopy is available from the literature as well. Using two diagnostic diagrams (the BPT and the WHAN) we provide a nuclear and an integrated spectral classification for the HRS galaxies. The BPT and the WHAN methods for nuclei consistently give a frequency of 53-64% HII, around 21-27% AGNs (including TRAN), and 15-20% of PAS (including RET), whereas for integrated spectra they give 69-84% HII, 4-11% of AGNs and 12-20% PAS. Solely among late-type galaxies (LTGs) do the nuclear percentages become 67-77% HII, 22-27% AGNs (including TRAN), and only 1-7% of PAS. For the integrated spectra these frequencies become: 80-85% HII, 9-11% AGNs and 4-9% PAS. We find that the fraction of HII region-like spectra is strongly anticorrelated with the stellar mass. On the contrary the frequency of AGNs increases significantly with stellar mass, such that at M*>10^10.0^M_{sun}_~66% of the LTGs are AGNs or TRAN. Moreover there is not a significant dependence of the frequency of AGNs as a function of environment: AGNs+TRAN above 10^9.0^M_{sun}_ are consistent with ~30% irrespective of their membership to the Virgo cluster, suggesting that the AGNs population is not sensitive to the environment. Finally, extrapolation of the global SF properties from the nuclear spectroscopy including aperture corrections leads to underestimates with respect to values derived from direct integrated H{alpha} photometry.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A116
- Title:
- HR study of massive supergiants in Per OB1
- Short Name:
- J/A+A/643/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Perseus OB1 association, including the h and chi Persei double cluster, is an interesting laboratory for the investigation of massive star evolution as it hosts one of the most populous groupings of blue and red supergiants (Sgs) in the Galaxy at a moderate distance and extinction. We discuss whether the massive O-type, and blue and red Sg stars located in the Per OB1 region are members of the same population, and examine their binary and runaway status. We gathered a total of 405 high-resolution spectra for 88 suitable candidates around 4.5 deg from the center of the association, and compiled astrometric information from Gaia DR2 for all of them. This was used to investigate membership and identify runaway stars. By obtaining high-precision radial velocity (RV) estimates for all available spectra, we investigated the RV distribution of the global sample (as well as different subsamples) and identified spectroscopic binaries (SBs). Most of the investigated stars belong to a physically linked population located at d=2.5+/-0.4kpc. We identify 79 confirmed or likely members, and 5 member candidates. No important differences are detected in the distribution of parallaxes when stars in h and chi Persei or the full sample are considered. In contrast, most O-type stars seem to be part of a differentiated population in terms of kinematical properties. In particular, the percentage of runaways among them (45%) is considerable higher than for the more evolved targets (which is lower than ~5% in all cases). A similar tendency is also found for the percentage of clearly detected SBs, which already decreases from 15% to 10% when the O star and B Sg samples are compared, respectively, and practically vanishes in the cooler Sgs. Concerning this latter result, our study illustrates the importance of taking the effect of the ubiquitous presence of intrinsic variability in the blue-to-red Sg domain into account to avoid the spurious identification of pulsating stars as SBs. All but 4 stars in our working sample (including 10 O giants/Sgs, 36 B Sgs, 9 B giants, 11 A/F Sgs, and 18 red Sgs) can be considered as part of the same (interrelated) population. However, any further attempt to describe the empirical properties of this sample of massive stars in an evolutionary context must take into account that an important fraction of the O stars is or likely has been part of a binary/multiple system. In addition, some of the other more evolved targets may have also been affected by binary evolution. In this line of argument, it is also interesting to note that the percentage of spectroscopic binaries within the evolved population of massive stars in Per OB1 is lower by a factor 4-5 than in the case of dedicated surveys of O-type stars in other environments that include a much younger population of massive stars.
- 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.
