Aims. We present a new library of high-resolution synthetic spectra based on the stellar atmosphere code PHOENIX that can be used for a wide range of applications of spectral analysis and stellar parameter synthesis. Methods. The spherical mode of PHOENIX was used to create model atmospheres and to derive detailed synthetic stellar spectra from them. We present a new self-consistent way of describing micro-turbulence for our model atmospheres. Results. The synthetic spectra cover the wavelength range from 500 A to 5.5 μm with resolutions of R = 500 000 in the optical and near IR, R = 100 000 in the IR and Δλ = 0.1 A in the UV. The parameter space covers 2300 K ≤ Teff ≤ 12 000 K, 0.0 ≤ log g ≤ +6.0, −4.0 ≤ [Fe/H] ≤ +1.0, and −0.2 ≤ [α/Fe] ≤ +1.2. The library is a work in progress and we expect to extend it up to Teff = 25 000 K.

/pdf/a-new-extensive-library-of-phoenix-stellar-atmospheres-and-1arwdcamrf.pdf

A new extensive library of PHOENIX stellar atmospheres and synthetic spectra

Vienna atomic line database (VALD) is a collection of critically evaluated laboratory parameters for individual atomic transitions, complemented by theoretical calculations. VALD is actively used by astronomers for stellar spectroscopic studies—model atmosphere calculations, atmospheric parameter determinations, abundance analysis etc. The two first VALD releases contained parameters for atomic transitions only. In a major upgrade of VALD—VALD3, publically available from spring 2014, atomic data was complemented with parameters of molecular lines. The diatomic molecules C2, CH, CN, CO, OH, MgH, SiH, TiO are now included. For each transition VALD provides species name, wavelength, energy, quantum number J and Lande-factor of the lower and upper levels, radiative, Stark and van der Waals damping factors and a full description of electronic configurarion and term information of both levels. Compared to the previous versions we have revised and verify all of the existing data and added new measurements and calculations for transitions in the range between 20 A and 200 microns. All transitions were complemented with term designations in a consistent way and electron configurations when available. All data were checked for consistency: listed wavelength versus Ritz, selection rules etc. A new bibliographic system keeps track of literature references for each parameter in a given transition throughout the merging process so that every selected data entry can be traced to the original source. The query language and the extraction tools can now handle various units, vacuum and air wavelengths. In the upgrade process we had an intensive interaction with data producers, which was very helpful for improving the quality of the VALD content.

A major upgrade of the VALD database

We present a 0.8-5 μm spectral library of 210 cool stars observed at a resolving power of R ≡ λ/Δλ ~ 2000 with the medium-resolution infrared spectrograph, SpeX, at the 3.0 m NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. The stars have well-established MK spectral classifications and are mostly restricted to near-solar metallicities. The sample not only contains the F, G, K, and M spectral types with luminosity classes between I and V, but also includes some AGB, carbon, and S stars. In contrast to some other spectral libraries, the continuum shape of the spectra is measured and preserved in the data reduction process. The spectra are absolutely flux calibrated using the Two Micron All Sky Survey photometry. Potential uses of the library include studying the physics of cool stars, classifying and studying embedded young clusters and optically obscured regions of the Galaxy, evolutionary population synthesis to study unresolved stellar populations in optically obscured regions of galaxies and synthetic photometry. The library is available in digital form from the IRTF Web site.

The infrared telescope facility (irtf) spectral library: cool stars

We report the definite spectroscopic identification of 40 OB supergiants, giants and main sequence stars in the central parsec of the Galaxy. Detection of their absorption lines have become possible with the high spatial and spectral resolution and sensitivity of the adaptive optics integral Held spectrometer SPIFFI/SINFONI on the ESO VLT. Several of these OB stars appear to be helium and nitrogen rich. Almost all of the 80 massive stars now known in the central parsec (central arcsecond excluded) reside in one of two somewhat thick (|/R 0.14) rotating disks. These stellar disks have fairly sharp inner edges (R 1'') and surface density profiles that scale as R−2. We do not detect any OB stars outside the central 0.5 pc. The majority of the stars in the clockwise system appear to be on almost circular orbits, whereas most of those in the 'counter-clockwise' disk appear to be on eccentric orbits. Based on its stellar surface density distribution and dynamics we propose that IRS 13E is an extremely dense cluster (ρcore 3 × 108M⊙ pc−3), which has formed in the counter-clockwise disk. The stellar contents of both systems are remarkably similar, indicating a common age of 6±2 Myr. The K-band luminosity function of the massive stars suggests a top-heavy mass function and limits the total stellar mass contained in both disks to 1.5 × 104 M⊙. Our data strongly favor in situ star formation from dense gas accretion disks for the two stellar disks. This conclusion is very clear for the clockwise disk and highly plausible for the counter-clockwise system.

https://iopscience.iop.org/article/10.1086/503273/pdf

The two young star disks in the central parsec of the galaxy: properties, dynamics and formation

We present a 0.8 -5 micron spectral library of 210 cool stars observed at a resolving power of R = lambda / Delta lambda ~ 2000 with the medium-resolution infrared spectrograph, SpeX, at the 3.0 m NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. The stars have well established MK spectral classifications and are mostly restricted to near-solar metallicities. The sample contains the F, G, K, and M spectral types with luminosity classes between I and V, but also includes some AGB, carbon, and S stars. In contrast to some other spectral libraries, the continuum shape of the spectra are measured and preserved in the data reduction process. The spectra are absolutely flux calibrated using Two Micron All Sky Survey (2MASS) photometry. Potential uses of the library include studying the physics of cool stars, classifying and studying embedded young clusters and optically obscured regions of the Galaxy, evolutionary population synthesis to study unresolved stellar populations in optically-obscured regions of galaxies, and synthetic photometry. The library is available in digital form from the IRTF website.

The Infrared Telescope Facility (IRTF) Spectral Library: Cool Stars

An Atlas of 115 medium-resolution K-band (2.0-2.4 μm) stellar spectra, spanning spectral types O-M and luminosity types I-V, is presented. K-band spectra are also presented for one N- and one J-type carbon star. A time series of spectra is presented for an S-type Mira variable. All the spectra are at a resolution of ~3000 (1.4 cm-1) and have had the terrestrial absorption removed by dividing by a featureless spectrum. The spectra are plotted with the major spectral features identified and are available digitally.

Medium-Resolution Spectra of Normal Stars in the K Band

On the thermal structure of Uranus

We have identified lines from the 0-3, 0-4, 0-5, 0-6, 0-7, 1-3, 1-4, 1-7, and 1-8 bands of the 24MgH B' 2Σ+-X 2Σ+ transition in sunspot umbral spectra. Lines of the 0-7 and 1-8 bands in the uncluttered 7500 A region are the most obvious, but B' 2Σ+-X 2Σ+ lines have been tracked as far to the blue as 5300 A. In combination with weak lines of the 0-7 bands of the 25MgH and 26MgH isotopes, the solar isotope ratio 24Mg:25Mg:26Mg has been measured as 76:12:12, in agreement with the much better determined terrestrial ratio 79:10:11. The intensity distribution of bands with v'' from 4 to 8 has been measured and found to show no anomalies; the excitation temperature of 3100 K agrees well with a value of 3200 K determined from SiO in a sunspot spectrum. The lines of the MgH B' 2Σ+-X 2Σ+ transition are much more cleanly separated and much less blended than lines from the stronger A 2Π-X 2Σ+ transition. The B' 2Σ+-X 2Σ+ lines should prove useful in isotopic abundance analyses for stars where the A 2Π-X 2Σ+ transition is too strong to yield useful results.

The MgH B' 2Σ+-X 2Σ+ Transition: A New Tool for Studying Magnesium Isotope Abundances

Infrared Absorption and Emission Spectra of SiO

The seasonal variation of the thermal structure of the atmosphere of Uranus

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