A New Stellar Atmosphere Grid and Comparisons with HST/STIS CALSPEC Flux Distributions

The Space Telescope Imaging Spectrograph (STIS) has measured the spectral energy distributions (SEDs) for several stars of types O, B, A, F, and G. These absolute fluxes from the CALSPEC database are fit with a new spectral grid computed from the ATLAS-APOGEE ATLAS9 model atmosphere database using a chi-square minimization technique in four parameters. The quality of the fits are compared for complete LTE grids by Castelli & Kurucz (CK04) and our new comprehensive LTE grid (BOSZ). For the cooler stars, the fits with the MARCS LTE grid are also evaluated, while the hottest stars are also fit with the NLTE Lanz & Hubeny OB star grids. Unfortunately, these NLTE models do not transition smoothly in the infrared to agree with our new BOSZ LTE grid at the NLTE lower limit of Teff =15,000K. The new BOSZ grid is available via the Space Telescope Institute MAST archive and has a much finer sampled IR wavelength scale than CK04, which will facilitate the modeling of stars observed by the James Webb Space Telescope (JWST). Our result for the angular diameter of Sirius agrees with the ground- based interferometric value.

[1]  N. Grevesse,et al.  Standard Solar Composition , 1998 .

[2]  I. Hubeny,et al.  BINARY STAR SYNTHETIC PHOTOMETRY AND DISTANCE DETERMINATION USING BINSYN , 2013 .

[3]  S. Price,et al.  Spectral Irradiance Calibration in the Infrared. XV. Absolute Calibration of Standard Stars by Experiments on the Midcourse Space Experiment , 2004 .

[4]  Ralph C. Bohlin,et al.  HUBBLE SPACE TELESCOPE CALSPEC FLUX STANDARDS: SIRIUS (AND VEGA) , 2014 .

[5]  M. Asplund,et al.  The Solar Chemical Composition , 2007 .

[6]  The Angular Diameter and Fundamental Parameters of Sirius A , 2010, Publications of the Astronomical Society of Australia.

[7]  R. Davies,et al.  Astronomical Society of the Pacific Conference Series , 2010 .

[8]  R. Kurucz.  Model atmospheres for G, F, A, B, and O stars , 1979 .

[9]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .

[10]  Astrophysics,et al.  The virtual observatory service TheoSSA: Establishing a database of synthetic stellar flux standards - I. NLTE spectral analysis of the DA-type white dwarf G191−B2B , 2013, 1308.6450.

[11]  R. Bohlin,et al.  NICMOS SPECTROPHOTOMETRY AND MODELS FOR A STARS , 2008, 0807.2782.

[12]  H. Ferguson,et al.  ABSOLUTE FLUX CALIBRATION OF THE IRAC INSTRUMENT ON THE SPITZER SPACE TELESCOPE USING HUBBLE SPACE TELESCOPE FLUX STANDARDS , 2011, 1103.3469.

[13]  Nikolai Piskunov,et al.  Modelling of Stellar Atmospheres , 2003 .

[14]  S. Deustua,et al.  The Gaia DR1 Mass-Radius Relation for White Dwarfs , 2016, 1611.00629.

[15]  R. Bohlin.  HUBBLE SPACE TELESCOPE SPECTROPHOTOMETRY AND MODELS FOR SOLAR ANALOGS , 2010, 1002.4381.

[16]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .

[17]  M. Asplund,et al.  The chemical composition of the Sun , 2009, 0909.0948.

[18]  Harry Partridge,et al.  The determination of an accurate isotope dependent potential energy surface for water from extensive ab initio calculations and experimental data , 1997 .

[19]  Ivan Hubeny,et al.  A Grid of NLTE Line-blanketed Model Atmospheres of Early B-Type Stars , 2007 .

[20]  Kjell Eriksson,et al.  A grid of MARCS model atmospheres for late-type stars. I. Methods and general properties , 2008, 0805.0554.

[21]  P. Coelho.  A new library of theoretical stellar spectra with scaled-solar and α-enhanced mixtures , 2014, 1404.3243.

[22]  F. Castelli,et al.  New ATLAS9 And MARCS Model Atmosphere Grids For The Apache Point Observatory Galactic Evolution Experiment (APOGEE) , 2012 .

[23]  C. Leitherer,et al.  Synthetic Spectra of H Balmer and He I Absorption Lines. I. Stellar Library , 1999, astro-ph/9907115.

[24]  A. Tielens,et al.  Pixie Dust: The Silicate Features in the Diffuse Interstellar Medium , 2005, astro-ph/0510156.

[25]  D. Schwenke.  Opacity of TiO from a coupled electronic state calculation parametrized by abinitio and experimental data , 1998 .

[26]  Ivan Hubeny,et al.  A Grid of Non-LTE Line-blanketed Model Atmospheres of O-Type Stars , 2002, astro-ph/0210157.