Far-Ultraviolet and Optical Spectroscopy of the Detached White Dwarf-M Dwarf Binary RE J1629+780
Abstract
We present optical and far ultraviolet observations, including IUE high and low dispersion spectroscopy of the (DA2+dM4-5) close binary, RE J1629+780, a very bright ROSAT EUV source. The optical data reveal emission reversals in the cores of the Balmer lines, which vary in strength but reveal no evidence of wavelength shifts reflecting orbital motion, suggesting that the red dwarf and the white dwarf are widely separated. Thus it is unlikely that irradiation plays a dominant role in the activity of the red dwarf. One dramatic increase in the intensity of the H-beta emission strength in the course of one hour indicates that the observed intensity variations are most likely related to flare activity on the red dwarf. Our analysis of Balmer and Lyman alpha features yield Teff = 42,500 +- 1300K and log g = 7.6 +- 0.3 for the DA2 white dwarf, which is consistent with the overall 900 A to 3200 A energy distribution derived from Voyager and IUE low dispersion spectra. Our analysis of three IUE echelle spectra reveal numerous lines of interstellar origin. Using a total of 13 ISM features we find a mean radial velocity of -13.57 +- 1.66 km/s for the interstellar features. However we found no evidence of trace metal absorbers levitated or accreited in the white dwarf photosphere nor any evidence of circumstellar or wind features. We estimate a lower limit hydrogen layer mass of 2.1 X 10^-15 M_sun for a stratified atmosphere based upon the non-detection of He II (1640). Tighter constraints on the helium abundance and the hydrogen layer mass, from EUV and X-ray data, are presented for both homogeneous and stratified atmospheric configurations. (SECTION: Stars)
- Publication:
-
Publications of the Astronomical Society of the Pacific
- Pub Date:
- March 1995
- DOI:
- 10.1086/133544
- Bibcode:
- 1995PASP..107..232S
- Keywords:
-
- Abundance;
- Binary Stars;
- Emission Spectra;
- Optical Emission Spectroscopy;
- Radial Velocity;
- Red Dwarf Stars;
- Ultraviolet Spectroscopy;
- White Dwarf Stars;
- Balmer Series;
- Data Reduction;
- Energy Distribution;
- H Alpha Line;
- Interstellar Matter;
- Iue;
- Lyman Alpha Radiation;
- Rosat Mission;
- Spectrum Analysis;
- Astronomy;
- WHITE DWARFS;
- STARS: INDIVIDUAL: RE J1629+780;
- BINARIES: CLOSE