2006A&A...459..187P


C.D.S. - SIMBAD4 rel 1.7 - 2020.01.19CET09:16:55

2006A&A...459..187P - Astronomy and Astrophysics, volume 459, 187-197 (2006/11-3)

Average hard X-ray emission from NS LMXBs: observational evidence of different spectral states in NS LMXBs.

PAIZIS A., FARINELLI R., TITARCHUK L., COURVOISIER T.J.-L., BAZZANO A., BECKMANN V., FRONTERA F., GOLDONI P., KUULKERS E., MEREGHETTI S., RODRIGUEZ J. and VILHU O.

Abstract (from CDS):

We studied and compared the long-term average hard X-ray (>20keV) spectra of a sample of twelve bright low-mass X-ray binaries hosting a neutron star (NS). Our sample comprises the six well studied Galactic Z sources and six Atoll sources, four of which are bright (``GX'') bulge sources while two are weaker ones in the 2-10keV range (H 1750-440 and H 1608-55). For all the sources of our sample, we analysed available public data and extracted average spectra from the IBIS/ISGRI detector on board INTEGRAL. We can describe all the spectral states in terms of the bulk motion Comptonisation scenario. We find evidence that bulk motion is always present, its strength is related to the accretion rate and it is suppressed only in the presence of high local luminosity. The two low-dim Atoll source spectra are dominated by photons up-scattered presumably due to dynamical and thermal Comptonisation in an optically thin, hot plasma. For the first time, we extend the detection of H 1750-440 up to 150keV. The Z and bright ``GX'' Atoll source spectra are very similar and are dominated by Comptonised blackbody radiation of seed photons, presumably coming from the accretion disc and NS surface, in an optically thick cloud with plasma temperature in the range of 2.5-3keV. Six sources show a hard tail in their average spectrum: Cyg X-2 (Z), GX 340+0 (Z), GX 17+2 (Z), GX 5-1 (Z), Sco X-1 (Z) and GX 13+1 (Atoll). This is the first detection of a hard tail in the X-ray spectrum of the peculiar GX 13+1. Using radio data from the literature we find, in all Z sources and bright ``GX'' Atolls, a systematic positive correlation between the X-ray hard tail (40-100keV) and the radio luminosity. This suggests that hard tails and energetic electrons causing the radio emission may have the same origin, most likely the Compton cloud located inside the NS magnetosphere.

Abstract Copyright:

Journal keyword(s): X-rays: binaries - binaries: close - stars: neutron

CDS comments: In the abstract H 1750-440 is a misprint for H 1705-440

Simbad objects: 16

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Number of rows : 16

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* QX Nor LXB 16 12 43.0 -52 25 23           ~ 817 1
2 V* V818 Sco LXB 16 19 55.0688745859 -15 38 25.019920749 11.60 12.40 11.1     Oev 1518 0
3 4U 1642-45 LXB 16 45 47.7 -45 36 40           ~ 377 1
4 V* V1101 Sco LXB 17 05 44.4915929414 -36 25 23.049863107   20.10 18.6     ~ 405 0
5 4U 1705-44 LXB 17 08 54.470 -44 06 07.35           ~ 352 0
6 V* V2216 Oph LXB 17 31 44.17 -16 57 40.9 16.40 17.10 16.8     ~ 261 1
7 NAME Slow Burster LXB 17 31 57.73 -33 50 02.5           ~ 751 1
8 X Sgr X-1 LXB 17 47 56.0 -26 33 49           ~ 344 0
9 4U 1758-25 LXB 18 01 09.7308941918 -25 04 44.128444504           ~ 611 1
10 2XMM J180112.4-254436 LXB 18 01 12.40 -25 44 36.1           ~ 358 1
11 X Sgr X-3 LXB 18 01 32.3 -20 31 44           ~ 218 1
12 V* V5512 Sgr LXB 18 14 31.55 -17 09 26.7           K5III 347 0
13 V* NP Ser LXB 18 16 01.389 -14 02 10.62   18.8       K 597 2
14 4U 1850-086 LXB 18 53 04.89 -08 42 19.7 20.40 21.20 21.0     ~ 229 1
15 V* V1333 Aql LXB 19 11 16.05 +00 35 05.8 15.00 15.40 14.8     ~ 997 0
16 V* V1341 Cyg LXB 21 44 41.1544523872 +38 19 17.065856122 15.00 15.13 14.68 15.00   A9III 1064 1

    Equat.    Gal    SGal    Ecl

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2020.01.19-09:16:55

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