2001A&A...371.1056N


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.15CEST02:17:42

2001A&A...371.1056N - Astronomy and Astrophysics, volume 371, 1056-1064 (2001/6-1)

On the nature of the hard X-ray source 4U 2206+54.

NEGUERUELA I. and REIG P.

Abstract (from CDS):

The recent discovery of a ∼9.5d period in the X-ray lightcurve of the massive X-ray binary 4U 2206+54 has opened the possibility that it is a Be/X-ray binary with an unusually close orbit, which, together with its low intrinsic luminosity, suggests that the system is actually a Be + WD binary, in which a white dwarf accretes material from the dense circumstellar disc surrounding a classical Be star. In this paper we present new X-ray observations and for the first time high-resolution optical spectroscopy of the source. We show that both the X-ray behaviour and the characteristics of the optical counterpart, BD+53 2790, are more consistent with a neutron star accreting from the wind of an early-type star. The X-ray lightcurve shows irregular flaring and no indications of pulsations, while the very high hydrogen column density supports accretion from a dense wind. BD+53 2790 is shown not to be a classical Be star, as believed until now, but rather a very peculiar late O-type active star, exhibiting emission components in the HeII lines, complex spectral variability and strong wind resonance lines in the ultraviolet. Though many of the characteristics of the spectrum resemble those of the He-rich stars, the absence of HeI variability makes a connection unlikely. The spectrum is compatible with a composite of two stars of similar spectral type, though circumstantial evidence points to a single very peculiar active early-type star. This adds weight to the growing evidence that the traditional subdivisions of supergiant and Be/X-ray binaries fail to cover the whole phenomenology of massive X-ray binaries.

Abstract Copyright:

Journal keyword(s): stars: binaries: general - stars: early-type - X-rays: stars

Simbad objects: 12

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Number of rows : 12

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 V* DZ Tuc HXB 00 50 44.7076463726 -73 16 05.432580504 14.46 15.37 15.44   15.31 B0-B0.5V 69 0
2 V* V662 Cas HXB 01 18 02.6973905772 +65 17 29.829417242 12.27 11.99 11.14 10.33 9.58 B1Iae 226 0
3 V* V635 Cas HXB 01 18 31.9704429246 +63 44 33.071137750 17.05 16.64 15.19 14.34 13.22 B0.2Ve 650 0
4 V* X Per HXB 03 55 23.0778791365 +31 02 45.045745259 6.090 6.840 6.720     O9.5III 897 0
5 X LMC X-4 HXB 05 32 49.5558669817 -66 22 13.202534152   13.9 14.0     O8III 597 0
6 * sig Ori E Y*O 05 38 47.2050001416 -02 35 40.514907495 5.66 6.38 6.46 6.84 7.08 B2IV-Vp_He 392 0
7 HD 245770 HXB 05 38 54.5749436467 +26 18 56.839215267 9.30 9.84 9.39 8.77 8.30 O9/B0III/Ve 856 0
8 V* V441 Pup HXB 07 28 53.5787769417 -26 06 28.895160996 11.27 12.29 11.83 11.53   O5Ve 65 0
9 V* GP Vel HXB 09 02 06.8610736194 -40 33 16.896402010 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1351 0
10 V* V479 Sct HXB 18 26 15.0561532140 -14 50 54.249464136 12.02 12.23 11.27 11.04   ON6V((f))z 483 2
11 4U 1907+09 HXB 19 09 37.9 +09 49 49   19.41 16.35 14.40 12.53 O8.5Iab 304 1
12 BD+53 2790 HXB 22 07 56.2368407539 +54 31 06.405811141 9.4 10.11 9.84 9.64 9.43 O9.5Vep 171 0

    Equat.    Gal    SGal    Ecl

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2019.10.15-02:17:43

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