2006A&A...457..595K


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.25CET20:40:05

2006A&A...457..595K - Astronomy and Astrophysics, volume 457, 595-610 (2006/10-2)

VLT/UVES spectroscopy of Wray 977, the hypergiant companion to the X-ray pulsar GX 301-2.

KAPER L., VAN DER MEER A. and NAJARRO F.

Abstract (from CDS):

Model atmosphere fits to high-resolution optical spectra of Wray 977 confirm the B hypergiant classification of the massive companion to the X-ray pulsar GX301-2. The models give a radius of 62R, an effective temperature of 18100K and a luminosity of 5x105L. These values are somewhat reduced compared to the stellar parameters of Wray 977 measured previously. The deduced mass-loss rate and terminal velocity of the stellar wind are 10–5M/yr and 305km/s, respectively. The interstellar NaI D absorption indicates that Wray 977 is located behind the first intersection with the Sagittarius-Carina spiral arm (1-2.5kpc) and probably belongs to the stellar population of the Norma spiral arm at a distance of 3-4kpc. The luminosity derived from the model atmosphere is consistent with this distance (3kpc). The luminosity of the wind-fed X-ray pulsar (LX∼1037erg/s) is in good accordance with the Bondi-Hoyle mass accretion rate. The spectra obtained with UVES on the Very Large Telescope (VLT) cover a full orbit of the system, including periastron passage, from which we derive the radial-velocity curve of the B hypergiant. The measured radial-velocity amplitude is 10±3km/s yielding a mass ratio q=MX/Mopt=0.046±0.014. The absence of an X-ray eclipse results in a lower limit to the mass of Wray 977 of 39M. An upper limit of 68 or 53M is derived for the mass of Wray 977 adopting a maximum neutron star mass of 3.2 or 2.5M, respectively. The corresponding lower limit to the system inclination is i>44°, supporting the view that the dip in the X-ray lightcurve is due to absorption by the dense stellar wind of Wray 977 (Leahy, 2002A&A...391..219L). The ``spectroscopic'' mass of Wray 977 is 43±10M, consistent with the range in mass derived from the binarity constraints. The mass of the neutron star is 1.85±0.6M. Time series of spectral lines formed in the dense stellar wind (e.g. HeI 5876Å and H α) indicate the presence of a gas stream trailing the neutron star in its orbit. The long-term behaviour of the H α equivalent width exhibits strong variations in wind strength; the sampling of the data is insufficient to conclude whether a relation exists between wind mass-loss rate and pulsar spin period.

Abstract Copyright:

Journal keyword(s): stars: binaries: close - stars: evolution - stars: individual: Wray 977 - stars: pulsars: individual: GX301-2 - stars: supergiants - X-rays: stars

Simbad objects: 14

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Number of rows : 14

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 V* GP Vel HXB 09 02 06.8610736194 -40 33 16.896402010 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1385 0
2 HD 103779 * 11 56 57.5477276437 -63 14 56.724935031 6.35 7.185 7.220 8.32   B0/1II 91 0
3 HD 104683 * 12 03 13.6096227879 -64 21 04.680567729 7.18 7.94 7.94 8.75   B1Ib/II 38 0
4 V* BP Cru HXB 12 26 37.5607088371 -62 46 13.259605389   12.70 10.66     B1.5Iaeq 614 0
5 WR 47a WR* 12 45 51.2509108395 -64 09 38.049177096   17.25 15.30     WN8h 23 0
6 HD 111904 V* 12 53 21.8939526500 -60 19 42.561485784 5.75 6.05 5.77 7.09   B9Iab 101 0
7 HD 113012 * 13 01 41.5337273990 -60 04 35.170402362 7.46 8.23 8.13 8.98   B0III 64 0
8 Ass Cen OB 1 As* 13 02 -61.4           ~ 104 0
9 HD 116852 * 13 30 23.5190459533 -78 51 20.544585252 8.29 8.38 8.47     O8.5II-III((f)) 137 1
10 NAME Car-Sgr Arm PoG 15 00 -40.0           ~ 440 1
11 NAME Nor Arm PoG 16 00 -50.0           ~ 354 0
12 HD 153919 HXB 17 03 56.7728262865 -37 50 38.912077679 6.06 6.78 6.51 6.08 5.90 O6Iafcp 765 1
13 4U 1907+09 HXB 19 09 37.9 +09 49 49   19.41 16.35 14.40 12.53 O8.5Iab 310 1
14 NAME Nor-Cen Arm PoG ~ ~           ~ 5 0

    Equat.    Gal    SGal    Ecl

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