2006A&A...449..687R


Query : 2006A&A...449..687R

2006A&A...449..687R - Astronomy and Astrophysics, volume 449, 687-698 (2006/4-2)

Wind accretion in the massive X-ray binary 4U 2206+54: abnormally slow wind and a moderately eccentric orbit.

RIBO M., NEGUERUELA I., BLAY P., TORREJON J.M. and REIG P.

Abstract (from CDS):

Massive X-ray binaries are usually classified by the properties of the donor star in classical, supergiant and Be X-ray binaries, the main difference being the mass transfer mechanism between the two components. The massive X-ray binary 4U 2206+54 does not fit in any of these groups, and deserves a detailed study to understand how the transfer of matter and the accretion on to the compact object take place. To this end we study an IUE spectrum of the donor and obtain a wind terminal velocity (v) of ∼350km/s, which is abnormally slow for its spectral type. We also analyse here more than 9 years of available RXTE/ASM data. We study the long-term X-ray variability of the source and find it to be similar to that observed in the wind-fed supergiant system Vela X-1, reinforcing the idea that 4U 2206+54 is also a wind-fed system. We find a quasi-period decreasing from ∼270 to ∼130d, noticed in previous works but never studied in detail. We discuss possible scenarios for its origin and conclude that long-term quasi-periodic variations in the mass-loss rate of the primary are probably driving such variability in the measured X-ray flux. We obtain an improved orbital period of P_ orb_=9.5591±0.0007d with maximum X-ray flux at MJD 51856.6±0.1. Our study of the orbital X-ray variability in the context of wind accretion suggests a moderate eccentricity around 0.15 for this binary system. Moreover, the low value of v solves the long-standing problem of the relatively high X-ray luminosity for the unevolved nature of the donor, BD +53 2790, which is probably an O9.5V star. We note that changes in v and/or the mass-loss rate of the primary alone cannot explain the different patterns displayed by the orbital X-ray variability. We finally emphasize that 4U 2206+54, together with LS 5039, could be part of a new population of wind-fed HMXBs with main sequence donors, the natural progenitors of supergiant X-ray binaries.

Abstract Copyright:

Journal keyword(s): X-rays: binaries - X-rays: individuals: 4U 2206+54 - stars: individual: BD +53 2790 - stars: winds, outflows - stars: variables: general - stars: emission-line, Be

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 - 2021
#notes
1 HD 108 SB* 00 06 03.3885906204 +63 40 46.771682957 6.79 7.58 7.40     O4-8f?p 309 0
2 LS I +61 303 HXB 02 40 31.6641883136 +61 13 45.591138110 11.27 11.61 10.75 10.19 9.55 B0Ve 787 2
3 * tet01 Ori C SB* 05 35 16.4664092288 -05 23 22.897102710 4.20 5.15 5.13 4.91 4.73 O7Vp 1317 1
4 V* GP Vel HXB 09 02 06.8610736194 -40 33 16.896402010 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1402 0
5 HD 93521 * 10 48 23.5116139485 +37 34 13.089937784 5.67 6.79 7.03     O9.5IIInn 409 1
6 V* V779 Cen HXB 11 21 15.0920367078 -60 37 25.627505233   14.4 12.27     O9III/Veq 1014 0
7 V* QV Nor HXB 15 42 23.3633078550 -52 23 09.576918639   16.3 14.5     B0.2Ia:e 384 1
8 HD 153919 HXB 17 03 56.7728262865 -37 50 38.912077679 6.06 6.78 6.51 6.08 5.90 O6Iafcp 776 1
9 V* V479 Sct HXB 18 26 15.0561532140 -14 50 54.249464136 12.02 12.23 11.27 11.04   ON6V((f))z 516 2
10 HD 191612 SB* 20 09 28.6111448914 +35 44 01.287772714 7.40 8.07 7.80     O8fpe 223 0
11 BD+53 2790 HXB 22 07 56.2368407539 +54 31 06.405811141 9.4 10.11 9.84 9.64 9.43 O9.5Vep 181 0
12 BD+60 2522 Em* 23 20 44.5136097871 +61 11 40.528599394 8.46 9.08 8.67     O6.5(n)fp 203 1

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2021.10.20-00:49:17

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