Query : 2008A&A...485..773B

2008A&A...485..773B - Astronomy and Astrophysics, volume 485, 773-775 (2008/7-3)

Spectroscopic observations of the quiescent neutron star system 4U 2129+47 (=V1727 Cygni).


Abstract (from CDS):

In quiescence, the proposed optical counterpart to the neutron star, low mass X-ray binary 4U 2129+47 (V1727 Cyg) shows a spectrum consistent with a late F-type subgiant and no radial velocity variations on the 5.24 h binary period. This could imply that V1727 Cyg is a chance line of sight interloper. Radial velocity measurements, however, showed evidence for a longer term ∼40km/s shift, which suggested that 4U 2129+47 could be a hierarchical triple system, with the F-type star in a wide orbit about the inner low mass X-ray binary. In order to confirm the long-term radial velocity shift reported in Garcia et al. (1989ApJ...341L..75G) and its amplitude, we obtained spectroscopic observations of V1727 Cyg during 1996 and 1998 with the William Herschel Telescope using the ISIS spectrograph. We determined radial velocities from the ISIS spectra by means of the cross-correlation technique with a template spectrum. The resulting radial velocities show variations with a maximum amplitude of ∼40km/s, confirming previous results and supporting the F-type star as being the third body in a hierarchical triple system. The odds that this star could be an interloper are ∼3x10–6.

Abstract Copyright:

Journal keyword(s): X-rays: binaries - techniques: radial velocities - stars: individual: V1727 Cygni

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 V* V1727 Cyg LXB 21 31 26.2133156448 +47 17 24.512055396 16.75 17.05 16.4     ~ 238 0
2 BD+47 4219 * 23 37 46.4502159912 +48 38 30.527711052   11.239 10.731 10.661   F7 5 0
3 * iot Psc PM* 23 39 57.0413764 +05 37 34.647529 4.640 4.620 4.120 3.68 3.37 F7V 611 0

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