2008A&A...489..725R


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.27CET05:14:48

2008A&A...489..725R - Astronomy and Astrophysics, volume 489, 725-740 (2008/10-2)

Rapid spectral and timing variability of Be/X-ray binaries during type II outbursts.

REIG P.

Abstract (from CDS):

X-ray colour-colour (CD) and colour-intensity (HID) diagrams are powerful tools that allow investigation of spectral variability without assuming any spectral model. These diagrams have been used extensively for low-mass X-ray binaries and black-hole candidates, but very few applications have been found for high-mass X-ray binaries. We investigated the spectral and timing variability of four accreting X-ray pulsars with Be-type companions during major X-ray outbursts. The aim is to define source states based on the properties (noise components) of the aperiodic variability in correlation with the position in the colour-colour diagram. Different spectral states were defined according to the value of the X-ray colours and flux. Transient Be/X-ray binaries exhibit two branches in their colour-colour and colour-intensity diagrams: i) the horizontal branch corresponds to a low-intensity state and shows the highest fractional rms, similar to the the island state in atolls and horizontal branch in Z sources; ii) the diagonal branch corresponds to a high-intensity state, in which the source stays for about 75% of the total duration of the outburst. Despite the complexity of the power spectra due to the peaks of the pulse period and its harmonics, the aperiodic variability of Be/X-ray binaries can be described with a relatively low number of Lorentzian components. Some of these components can be associated with the same type of noise as seen in low-mass X-ray binaries, although the characteristic frequencies are about one order of magnitude lower. The analysis of the CD/HID and power spectra results in two different types of Be/X. While in 4U 0115+63, KS 1947+300 and EXO 2030+375 the hard colour decreases as the count rate decreases, it increases in V0332+53. The pattern traced by V0332+53 then results in a Z-shaped track, similar to the low-mass Z sources, without the flaring branch. In contrast, the horizontal branch in 4U 0115+63, KS 1947+300 and EXO 2030+375 corresponds to a low/soft state, which is not seen in other types of X-ray binaries. The noise at very low frequencies follows a power law in V0332+53 (like in LMXB Z), and it is flat-topped in 4U 0115+63, KS 1947+300, and EXO 2030+375 (like in LMXB atoll). V0332+53 shows a noise component coupled with the periodic variability that it is not seen in any of the other three sources.

Abstract Copyright:

Journal keyword(s): stars: emission-line, Be - stars: neutron - X-rays: binaries - stars: pulsars: general

Simbad objects: 15

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Number of rows : 15

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 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9697 1
2 RX J0111.2-7317 HXB 01 11 08.5772485083 -73 16 46.307693953 14.40 15.42 15.52   15.29 B0.5-1Ve 71 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 673 0
4 V* BQ Cam HXB 03 34 59.9116460415 +53 10 23.296351781   17.16 15.42 14.26 13.04 O8.5Ve 411 1
5 V* CM Tau Psr 05 34 31.93830 +22 00 52.1758           ~ 4864 1
6 M 1 SNR 05 34 31.94 +22 00 52.2           ~ 5702 4
7 V* V1055 Ori LXB 06 17 07.3 +09 08 13   18.80 18.5     ~ 521 1
8 V* QX Nor LXB 16 12 43.0 -52 25 23           ~ 846 1
9 4U 1722-30 LXB 17 27 33.25 -30 48 07.4     12.50     ~ 238 1
10 NAME Slow Burster LXB 17 31 57.73 -33 50 02.5     15.50     ~ 774 1
11 V* V4634 Sgr LXB 18 29 28.2 -23 47 49 18.90 19.40 19     ~ 298 0
12 X Aql X-1 LXB 19 11 16.0572031521 +00 35 05.876658556           ~ 1034 1
13 2MASS J19493548+3012317 HXB 19 49 35.4840244577 +30 12 31.775034731   15.16 14.22 13.53 12.88 B0Ve 140 1
14 GRO J2014+34 XB* 19 54 +30.1           ~ 32 1
15 V* V2246 Cyg HXB 20 32 15.2744631713 +37 38 14.839930326   22.16 19.41 17.32 15.18 B0Ve 382 0

    Equat.    Gal    SGal    Ecl

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