2002A&A...382..947K


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.23CEST00:58:12

2002A&A...382..947K - Astronomy and Astrophysics, volume 382, 947-973 (2002/2-2)

X-ray bursts at extreme mass accretion rates from GX 17+2.

KUULKERS E., HOMAN J., VAN DER KLIS M., LEWIN W.H.G. and MENDEZ M.

Abstract (from CDS):

We report on ten type I X-ray bursts originating from GX 17+2 in data obtained with the RXTE/PCA in 1996-2000. Three bursts were short in duration (∼10s), whereas the others lasted for ∼6-25min. All bursts showed spectral softening during their decay. There is no evidence for high-frequency (>100Hz) oscillations at any phase of the bursts. We see no correlations of the burst properties with respect to the persistent X-ray spectral properties, suggesting that in GX 17+2 the properties of the bursts do not correlate with inferred mass accretion rate. The presence of short bursts in GX 17+2 (and similar bright X-ray sources) is not accounted for in the current X-ray bursts theories at the high mass accretion rates encountered in this source. We obtain satisfactory results if we model the burst emission with a black body, after subtraction of the persistent pre-burst emission. The two-component spectral model does not fit the total burst emission whenever there is a black-body component present in the persistent emission. We conclude that in those cases the black-body contribution from the persistent emission is also present during the burst. This implies that, contrary to previous suggestions, the burst emission does not arise from the same site as the persistent black-body emission. The black-body component of the persistent emission is consistent with being produced in an expanded boundary layer, as indicated by recent theoretical work. Five of the long bursts showed evidence of radius expansion of the neutron star photosphere (independent of the spectral analysis method used), presumably due to the burst luminosity reaching the Eddington value. When the burst luminosity is close to the Eddington value, slight deviations from pure black-body radiation are seen at energies below ≃10keV. Similar deviations have been seen during (long) X-ray bursts from other sources; they can not be explained by spectral hardening models. The total persistent flux just before and after the radius expansion bursts is inferred to be up to a factor of 2 higher than the net peak flux of the burst. If both the burst and persistent emission are radiated isotropically, this would imply that the persistent emission is up to a factor of 2 higher than the Eddington luminosity. This is unlikely and we suggest that the persistent luminosity is close to the Eddington luminosity and that the burst emission is (highly) anisotropic (ξ∼2). Assuming that the net burst peak fluxes equal the Eddington limit, applying standard burst parameters (1.4M neutron star, cosmic composition, electron scattering opacity appropriate for high temperatures), and taking into account gravitational redshift and spectral hardening, we derive a distance to GX 17+2 of ∼8kpc, with an uncertainty of up to ∼30%.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - binaries: close - stars: individual (GX 17+2) - stars: neutron - X-rays: bursts

Simbad objects: 17

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Number of rows : 17

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* V818 Sco LXB 16 19 55.0688745859 -15 38 25.019920749 11.60 12.40 11.1     Oev 1512 0
2 4U 1642-45 LXB 16 45 47.7 -45 36 40           ~ 373 1
3 V* V1101 Sco LXB 17 05 44.4915929414 -36 25 23.049863107   20.10 18.6     ~ 401 0
4 X Oph X-2 X 17 08 23 -22 48.2           ~ 26 1
5 RX J1718.4-4029 LXB 17 18 24.13 -40 29 30.4           ~ 35 0
6 1H 1715-321 LXB 17 18 47.40 -32 10 40.0           ~ 72 0
7 4U 1722-30 LXB 17 27 33.25 -30 48 07.4           ~ 231 1
8 V* V2216 Oph LXB 17 31 44.17 -16 57 40.9 16.40 17.10 16.8     ~ 260 1
9 X Sgr X-1 LXB 17 47 56.0 -26 33 49           ~ 340 0
10 4U 1758-25 LXB 18 01 09.7308941918 -25 04 44.128444504           ~ 606 1
11 X Sgr X-3 LXB 18 01 32.3 -20 31 44           ~ 217 1
12 V* V5512 Sgr LXB 18 14 31.55 -17 09 26.7           K5III 346 0
13 V* NP Ser LXB 18 16 01.389 -14 02 10.62   18.8       K 592 2
14 X Sgr X-4 LXB 18 23 40.57 -30 21 40.6   19.06 18.81     ~ 886 1
15 4U 2129+12 LXB 21 29 58.3124 +12 10 02.670 14.50 15.70 15.8     ~ 300 1
16 V* V1341 Cyg LXB 21 44 41.1544523872 +38 19 17.065856122 15.00 15.20 14.7     A9III 1059 0
17 MXB 1730-355 X ~ ~           ~ 3 0

    Equat.    Gal    SGal    Ecl

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2019.10.23-00:58:12

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