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Astron. Astrophys. 318, 111-133 (1997)

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7. Accreting and related sources

Compared to other regions in the galactic plane this area in Cygnus is particularly void of accreting sources. The only catalogued X-ray binary is the low mass system 4U 2129+47 at l = [FORMULA] and b = [FORMULA] which is presently in an extended low state since the early 1980s (Pietsch et al. 1986). Our non detection is consistent with the faint ROSAT HRI source detected with a count rate of 0.004 cts s-1 during a pointed observation which took place about one year after the survey observations (Garcia 1994). The only cataclysmic variable appearing in our source list is V1500 Cyg, also known as Nova Cyg 75, which is detected at the rather low maximum likelihood of 7.6.

We identify RX J2130.3+4709 (index 84) with a WD+Me star close binary. The blue optical spectrum (see Motch et al. 1996a) displays heavily broadened Balmer lines typical of a rather cool white dwarf with superimposed narrow Balmer and Ca II H&K emission lines. In the red, the spectrum is dominated by that of a late Me star with strong TiO molecular bands and H [FORMULA] emission. Radial velocities of Balmer absorption and emission lines vary in opposite directions with an orbital period of [FORMULA] 12 hours. The white dwarf in RX J2130.3+4709 is too cool to contribute to the X-ray emission and the flux detected by ROSAT (1.6 10-2 cts s-1) probably arises from the Me star companion. In such a compact binary the late type star may be tidally locked to the white dwarf implying an enhanced rotational velocity and resulting coronal activity. RX J2130.3+4709 appears quite similar to RX J0458.9-6628 (Hutchings et al. 1995). We shall extensively discuss the properties of this system and its possible relation to cataclysmic variables in a forthcoming paper.

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998
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