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- ID:
- ivo://CDS.VizieR/J/ApJ/748/93
- Title:
- K-band spectra for 133 nearby M dwarfs
- Short Name:
- J/ApJ/748/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present K-band spectra for 133 nearby (d < 33 pc) M dwarfs, including 18 M dwarfs with reliable metallicity estimates (as inferred from an FGK type companion), 11 M dwarf planet hosts, more than 2/3 of the M dwarfs in the northern 8 pc sample, and several M dwarfs from the LSPM catalog. From these spectra, we measure equivalent widths of the Ca and Na lines, and a spectral index quantifying the absorption due to H_2_O opacity (the H_2_O-K2 index). Using empirical spectral type standards and synthetic models, we calibrate the H_2_O-K2 index as an indicator of an M dwarf's spectral type and effective temperature. We also present a revised relationship that estimates the [Fe/H] and [M/H] metallicities of M dwarfs from their Na I, Ca I, and H_2_O-K2 measurements. Comparisons to model atmosphere provide a qualitative validation of our approach, but also reveal an overall offset between the atomic line strengths predicted by models as compared to actual observations. Our metallicity estimates also reproduce expected correlations with Galactic space motions and H{alpha} emission line strengths, and return statistically identical metallicities for M dwarfs within a common multiple system. Finally, we find systematic residuals between our H_2_O-based spectral types and those derived from optical spectral features with previously known sensitivity to stellar metallicity, such as TiO, and identify the CaH1 index as a promising optical index for diagnosing the metallicities of near-solar M dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/494/1137
- Title:
- K-band spectral catalog of Quintuplet cluster
- Short Name:
- J/A+A/494/1137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Three very massive clusters are known to reside in the Galactic center region, the Arches cluster, the Quintuplet cluster, and the central parsec cluster, each of them rich in young hot stars. With new infrared instruments, this region is no longer obscured for the observer. For understanding these very massive clusters, it is essential to know their stellar inventory. We provide comprehensive spectroscopic data for the stellar population of the Quintuplet cluster that will form the basis of subsequent spectral analyses. Spectroscopic observations of the Quintuplet cluster were obtained with the Integral Field Spectrograph SINFONI-SPIFFI at the ESO-VLT, with the ESO VLT UT4 (Yepun) telescope between May and July 2006. The inner part of the Quintuplet cluster covered by 22 slightly overlapping fields, each of them of 8"x8" in size. The spectral range comprises the near-IR K-band from 1.94 to 2.45um. The 3D data cubes of the individual fields were flux-calibrated and combined to one contiguous cube, from which the spectra of all detectable point sources were extracted.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A19
- Title:
- K-band spectra of 6 LMC globular clusters
- Short Name:
- J/A+A/510/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Current stellar population models have arguably the largest uncertainties in the near-IR wavelength range, partly due to a lack of large and well calibrated empirical spectral libraries. In this paper we present a project whose aim it is to provide the first library of luminosity weighted integrated near-IR spectra of globular clusters to be used to test the current stellar population models and serve as calibrators for future ones. Our pilot study presents spatially integrated K-band spectra of three old (>=10Gyr) and metal poor ([Fe/H]~-1.4), and three intermediate age (1-2Gyr) and more metal rich ([Fe/H]~-0.4) globular clusters in the LMC.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/143
- Title:
- K-band spectra of stars within central 1pc of the MW
- Short Name:
- J/ApJ/809/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a metallicity analysis of 83 late-type giants within the central 1pc of the Milky Way. K-band spectroscopy of these stars was obtained with the medium spectral resolution integral-field spectrograph NIFS on Gemini North using laser-guided star adaptive optics. Using spectral template fitting with the MARCS synthetic spectral grid, we find that there is a large variation in the metallicity, with stars ranging from [M/H]<-1.0 to above solar metallicity. About 6% of the stars have [M/H]<-0.5. This result is in contrast to previous observations with smaller samples that show stars at the Galactic center having approximately solar metallicity with only small variations. Our current measurement uncertainties are dominated by systematics in the model, especially at [M/H]>0, where there are stellar lines not represented in the model. However, the conclusion that there are low-metallicity stars, as well as large variations in metallicity, is robust. The metallicity may be an indicator of the origin of these stars. The low-metallicity population is consistent with that of globular clusters in the Milky Way, but their small fraction likely means that globular cluster infall is not the dominant mechanism for forming the Milky Way nuclear star cluster. The majority of stars are at or above solar metallicity, which suggests they were formed closer to the Galactic center or from the disk. In addition, our results indicate that it will be important for star formation history analyses using red giants at the Galactic center to consider the effect of varying metallicity.
- ID:
- ivo://CDS.VizieR/J/AJ/121/97
- Title:
- K-band spectroscopy of ULIRGs
- Short Name:
- J/AJ/121/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared spectroscopy for a complete sample of 33 ultraluminous infrared galaxies at a resolution of R~1000. Most of the wavelength range from 1.80-2.20{mu}m in the rest frame is covered, including the Pa{alpha} and Br{gamma} hydrogen recombination lines, and the molecular hydrogen vibration-rotation 1-0 S(1) and S(3) lines. Other species, such as He I, [Fe II], and [Si VI] appear in the spectra as well, in addition to a number of weaker molecular hydrogen lines. Nuclear extractions for each of the individual galaxies are presented here, along with spectra of secondary nuclei, where available. The Pa{alpha} emission is seen to be highly concentrated on the nuclei, typically with very little emission extending beyond a radius of 1kpc. This survey was carried out primarily to search for signatures of active nuclei via velocity-broadened hydrogen recombination or the presence of the [Si VI] coronal line. These signatures are rare in the present sample, occurring in only two of the 33 galaxies. The extinction to the hydrogen recombination lines is investigated via the Pa{alpha}/Br{gamma} line ratio. It is found that visual extinctions to the nuclei in excess of 10mag are relatively common among ULIRGs and that visual extinctions greater than 25mag are necessary to conceal a QSO emitting half the total bolometric luminosity. The ionized hydrogen regions in many ULIRGs are sufficiently obscured that dust-enshrouded active galactic nuclei would remain hidden at 2{mu}m at the current level of sensitivity. The vibration-rotation lines of molecular hydrogen appear to be predominantly thermal in origin, with effective temperatures generally around 2200K. The relative nuclear velocities between double nucleus ULIRGs are investigated, through which it is inferred that the maximum deprojected velocity difference is ~200km.s-1. This figure is lower than the velocities predicted by physical models of strong interactions/mergers of large, gas-rich galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A110
- Title:
- K band spectrum of beta Pictoris b
- Short Name:
- J/A+A/633/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Beta Pictoris is arguably one of the most studied stellar systems outside of our own. Some 30 years of observations have revealed a highly-structured circumstellar disk, with rings, belts, and a giant planet: beta Pictoris b. However very little is known about how this system came into being. Our objective is to estimate the C/O ratio in the atmosphere of {beta} Pictoris b and obtain an estimate of the dynamical mass of the planet, as well as to refine its orbital parameters using high-precision astrometry. We used the GRAVITY instrument with the four 8.2m telescopes of the Very Large Telescope Interferometer to obtain K-band spectro-interferometric data on {beta} Pic b. We extracted a medium resolution (R=500) K-band spectrum of the planet and a high- precision astrometric position. We estimated the planetary C/O ratio using two different approaches (forward modeling and free retrieval) from two different codes (ExoREM and petitRADTRANS, respectively). Finally, we used a simplified model of two formation scenarios (gravitational collapse and core-accretion) to determine which can best explain the measured C/O ratio. Our new astrometry disfavors a circular orbit for beta Pic b (e=0.15^+0.05^_-0.04_). Combined with previous results and with Hipparcos/GAIA measurements, this astrometry points to a planet mass of M=12.7+/-2.2M_{Jup}_. This value is compatible with the mass derived with the free-retrieval code petitRADTRANS using spectral data only. The forward modeling and free-retrieval approches yield very similar results regarding the atmosphere of beta Pic b. In particular, the C/O ratios derived with the two codes are identical (0.43+/-0.05 vs $0.43^+0.04^_-0.03_). We argue that if the stellar C/O in beta Pic is Solar, then this combination of a very high mass and a low C/O ratio for the planet suggests a formation through core-accretion, with strong planetesimal enrichment.
- ID:
- ivo://CDS.VizieR/J/A+A/568/L13
- Title:
- K-band spectrum of the very massive star W49nr1
- Short Name:
- J/A+A/568/L13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Very massive stars (M>100M_{sun}_) are very rare objects, but have a strong influence on their environment. The formation of this kind of objects is of prime importance in star formation, but observationally still poorly constrained. We report on the identification of a very massive star in the central cluster of the star-forming region W49. We investigate near-infrared K-band spectroscopic observations of W49 from VLT/ISAAC together with JHK images obtained with NTT/SOFI and LBT/LUCI. We derive a spectral type of W49nr1, the brightest star in the dense core of the central cluster of W49.
- ID:
- ivo://CDS.VizieR/II/211
- Title:
- K-band survey in high galactic latitude
- Short Name:
- II/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The survey is a high galactic latitude, large area (552 square arcmin) blank-field sample to a 5{sigma} limit of K=17.3mag. Star-galaxy discrimination is performed. The infrared observations were made over the period 1987-1988, using the infrared camera IRCAM at the 3.8m UKIRTelescope at Mauna Kea, Hawai. The pixel size is 1.2arcsec. The redshift survey (spectro.dat) concerns 124 galaxies of the survey, and was carried out on the Anglo-Australian telescope and the William Herschel telescope at La Palma over the period 1990-1992, with a multi-fibre spectrograph for the brighter objects (R<19), long and multi-slit spectrographs for fainter objects.
- ID:
- ivo://CDS.VizieR/J/AJ/143/35
- Title:
- KCAL VERA 22 GHz calibrator survey
- Short Name:
- J/AJ/143/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed at 22GHz with the VLBI array VERA a sample of 1536 sources with correlated flux densities brighter than 200mJy at 8GHz. One half of target sources has been detected. The detection limit was around 200mJy. We derived the correlated flux densities of 877 detected sources in three ranges of projected baseline lengths. The objective of these observations was to determine the suitability of given sources as phase calibrators for dual-beam and phase-referencing observations at high frequencies. Preliminary results indicate that the number of compact extragalactic sources at 22GHz brighter than a given correlated flux density level is twice less than at 8GHz.