The table provides improved numerical relations between effective temperatures of stars, their B-V colors, and their bolometric corrections (BC) for the purpose of comparing theoretical stellar evolutionary calculations to color-magnitude diagrams of star clusters. Temperature and bolometric correction measurements for 335 stars from the literature form the observational basis for the transformations. Measured temperatures range from 2900 to 52500K.
A method of determination of the effective temperature of B, A and F main sequence stars is proposed, using the slope of the continuum between 3200A and 3600A. We have determined the Balmer jump and the effective temperatures for 235 main sequence stars.
The dependence on the temperature of photospheric line-depth ratios (LDRs) in the spectral range 619.0-628.0nm is investigated by using a sample of 174 ELODIE Archive stellar spectra of luminosity class from V to III. The rotational broadening effect on LDRs is also studied. We provide useful calibrations of effective temperature versus LDRs for giant and main sequence stars with 3800<~T_eff_<~6000K and vsini in the range 0-30km/s. We found that, with the exception of very few line pairs, LDRs, measured at a spectral resolution as high as 42000, depend on vsini and that, by neglecting the rotational broadening effect, the T_eff_ determination can be wrong by ~100K in the worst cases.
The ability to perform detailed chemical analysis of Sun-like F-, G-, and K-type stars is a powerful tool with many applications, including studying the chemical evolution of the Galaxy and constraining planet formation theories. Unfortunately, complications in modeling cooler stellar atmospheres hinders similar analyses of M dwarf stars. Empirically calibrated methods to measure M dwarf metallicity from moderate-resolution spectra are currently limited to measuring overall metallicity and rely on astrophysical abundance correlations in stellar populations. We present a new, empirical calibration of synthetic M dwarf spectra that can be used to infer effective temperature, Fe abundance, and Ti abundance. We obtained high-resolution (R~25000), Y-band (~1{mu}m) spectra of 29 M dwarfs with NIRSPEC on Keck II. Using the PHOENIX stellar atmosphere modeling code (version 15.5), we generated a grid of synthetic spectra covering a range of temperatures, metallicities, and alpha-enhancements. From our observed and synthetic spectra, we measured the equivalent widths of multiple Fe I and Ti I lines and a temperature-sensitive index based on the FeH band head. We used abundances measured from widely separated solar-type companions to empirically calibrate transformations to the observed indices and equivalent widths that force agreement with the models. Our calibration achieves precisions in Teff, [Fe/H], and [Ti/Fe] of 60K, 0.1dex, and 0.05dex, respectively, and is calibrated for 3200K<Teff<4100K, -0.7<[Fe/H]<+0.3, and -0.05<[Ti/Fe]<+0.3. This work is a step toward detailed chemical analysis of M dwarfs at a precision similar to what has been achieved for FGK stars.
Interferometric radius measurements provide a direct probe of the fundamental parameters of M dwarfs. However, interferometry is within reach for only a limited sample of nearby, bright stars. We use interferometrically measured radii, bolometric luminosities, and effective temperatures to develop new empirical calibrations based on low-resolution, near-infrared spectra. We find that H-band Mg and Al spectral features are good tracers of stellar properties, and derive functions that relate effective temperature, radius, and log luminosity to these features. The standard deviations in the residuals of our best fits are, respectively, 73K, 0.027R_{sun}_, and 0.049dex (an 11% error on luminosity). Our calibrations are valid from mid K to mid M dwarf stars, roughly corresponding to temperatures between 3100 and 4800K. We apply our H-band relationships to M dwarfs targeted by the MEarth transiting planet survey and to the cool Kepler Objects of Interest (KOIs). We present spectral measurements and estimated stellar parameters for these stars. Parallaxes are also available for many of the MEarth targets, allowing us to independently validate our calibrations by demonstrating a clear relationship between our inferred parameters and the stars' absolute K magnitudes. We identify objects with magnitudes that are too bright for their inferred luminosities as candidate multiple systems. We also use our estimated luminosities to address the applicability of near-infrared metallicity calibrations to mid and late M dwarfs. The temperatures we infer for the KOIs agree remarkably well with those from the literature; however, our stellar radii are systematically larger than those presented in previous works that derive radii from model isochrones. This results in a mean planet radius that is 15% larger than one would infer using the stellar properties from recent catalogs. Our results confirm the derived parameters from previous in-depth studies of KOIs 961 (Kepler-42), 254 (Kepler-45), and 571 (Kepler-186), the latter of which hosts a rocky planet orbiting in its star's habitable zone.
With the {Delta}a photometric system, it is possible to study very distant galactic and even extragalactic clusters with a high level of accuracy. The new calibration presented is a powerful extension. Because no a-priori reddening-free photometric parameters are available for the investigated spectral range, we have applied the dereddening calibrations of the Stromgren uvby{beta} system and compared them with extinction models for the Milky Way. We derived an empirical temperature calibration for the {Delta}a photometric system for A-type to mid F-type with a mean of the error for the whole sample of {Delta}T(eff) is 134K which is lower than the value in Paper I (Paunzen et al., 2005, Cat. <J/A+A/444/941>) for hotter stars. No statistically significant effect of the rotational velocity on the precision of the calibration was found.
The catalog contains values of theta [= 5040/T_eff_] for 951 F-K stars which are on or near the main sequence. Values of Cousins R-I are also given for most stars.
Temperature effects on spectra of olivine particles
Short Name:
J/A+A/449/583
Date:
21 Oct 2021
Publisher:
CDS
Description:
The absorption spectra of the olivine particles of different Mg/Fe content were measured in the infrared spectral region between 5 and 100{mu}m, while the particles were continuously cooled down to 10K. Measurements independently carried out on different samples of synthetic forsterite, natural olivine, and synthetic fayalite at laboratories in Kyoto and Jena. The positions of the olivine infrared bands were measured for these samples in detail at up to seven individual temperatures in the interval between 300K and 10K. According to the different widths of the olivine bands in different wavelength regions, spectral resolutions of 2, 1, 0.5, 0.25, 0.2, and 0.125cm^-1^ were used in order to measure the band positions with high accuracy.
Observational identification of a solid evolutionary sequence for high-mass star-forming regions is still missing. Spectroscopic observations give the opportunity to test possible schemes and connect the phases identified to physical processes. We aim to use the progressive heating of the gas caused by the feedback of high-mass young stellar objects to prove the statistical validity of the most common schemes used to observationally define an evolutionary sequence for high-mass clumps, and characterise the sensitivity of different tracers to this process. From the spectroscopic follow-ups carried out towards submillimeter continuum (dust) emission-selected massive clumps (the ATLASGAL TOP100 sample) with the IRAM 30m, Mopra, and APEX telescopes between 84GHz and 365GHz, we selected several multiplets of CH_3_N, CH_3_CH, and CH_3_H emission lines to derive and compare the physical properties of the gas in the clumps along the evolutionary sequence, fitting simultaneously the large number of lines that these molecules have in the observed band. Our findings are compared with results obtained from optically thin CO isotopologues, dust, and ammonia from previous studies on the same sample. The chemical properties of each species have a major role on the measured physical properties. Low temperatures are traced by ammonia, methanol, and CO (in the early phases), the warm and dense envelope can be probed with CH_3_N, CH_3_CH, and, in evolved sources where CO is abundant in the gas phase, via its optically thin isotopologues. CH_3_H and CH_3_N are also abundant in the hot cores, and we suggest that their high-excitation transitions are good tools to study the kinematics in the hot gas associated with the inner envelope surrounding the young stellar objects that these clumps are hosting. All tracers show, to different degrees according to their properties, progressive warming with evolution. The relation between gas temperature and the luminosity-to-mass (L/M) ratio is reproduced by a simple toy model of a spherical, internally heated clump.
The catalog contains mean values of [Fe/H] (with rms errors) for 1117 evolved G-K stars. Literature references are given for the source data, which are all from high-dispersion or related work. A number of literature sources which are not used are listed with their reasons for being set aside. A FORTRAN program for listing samples from the catalog is also included. The temper.dat file contains values of Johnson V-K, {theta} [=5040/T_eff_] and E(B-V) for 346 evolved G-K stars.