Institut für Astronomie und Astrophysik Abteilung Astronomie Sand 1, D-72076 Tübingen, Germany

Preprint 04/14

The virtual observatory service TheoSSA: Establishing a database of synthetic stellar flux standards. II. NLTE spectral analysis of the OB-type subdwarf Feige 110

T. Rauch (1), A. Rudkowski (1), D. Kampka (1), K. Werner (1), J. W. Kruk (2), S. Moehler (3)

(1) Institute for Astronomy and Astrophysics, Eberhard Karls University, Tübingen, Germany
(2) NASA Goddard Space Flight Center, Greenbelt, USA
(3) European Southern Observatory, Garching, Germany

To be published in: A&A

Abstract. In the framework of the Virtual Observatory (VO), the German Astrophysical Virtual Observatory (GAVO) developed the registered service TheoSSA (Theoretical Stellar Spectra Access). It provides easy access to stellar spectral energy distributions (SEDs) and is intended to ingest SEDs calculated by any model-atmosphere code, generally for all effective temperature, surface gravities, and elemental compositions. We will establish a database of SEDs of flux standards that are easily accessible via TheoSSA's web interface.
The OB-type subdwarf Feige 110 is a standard star for flux calibration. State-of-the-art non-local thermodynamic equilibrium (NLTE) stellar-atmosphere models that consider opacities of species up to trans-iron elements will be used to provide a reliable synthetic spectrum to compare with observations.
In case of Feige 110, we demonstrate that the model reproduces not only its overall continuum shape from the far-ultraviolet (FUV) to the optical wavelength range but also the numerous metal lines exhibited in its FUV spectrum.
We present a state-of-the-art spectral analysis of Feige 110. We determined T_eff = 47250 ± 2000 K, log g = 6.00 ± 0.20, and the abundances of He, N, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, and Ge. Ti, V, Mn, Co, Zn, and Ge were identified for the first time in this star. Upper abundance limits were derived for C, O, Si, Ca, and Sc.
The TheoSSA database of theoretical SEDs of stellar flux standards guarantees that the flux calibration of astronomical data and cross-calibration between different instruments can be based on models and SEDs calculated with state-of-the-art model-atmosphere codes.
 
Key words: Standards Stars: abundances Stars: atmospheres Stars: individual: Feige 110 Stars: subdwarfs Virtual observatory tools

Preprint (1,41 Mb PDF file including figures)

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