GX 349+2 (Sco X-2): An odd-ball among the Z sources
| dc.creator | Kuulkers, Erik | |
| dc.creator | van der Klis, Michiel | |
| dc.date | 1997-12-23 | |
| dc.date.accessioned | 2026-07-07T02:25:40Z | |
| dc.date.available | 2026-07-07T02:25:40Z | |
| dc.description | We report on about 4 hrs of observations made with the Rossi X-ray Timing Explorer on 1997 May 2 of the low-mass X-ray binary and Z source GX 349+2 (Sco X-2). Initially the source was in the normal branch (NB), later it moved to the flaring branch (FB). In the NB the power spectra reveal a broad (FWHM ~16 Hz) noise component peaking near 9 Hz, with a fractional rms amplitude of ~3% (2-30 keV). This noise component does not resemble the strong quasi-periodic oscillations (QPO) usually seen in the NB of other Z sources. We set 95% confidence upper limits on the fractional rms of ~0.9% (2-30 keV) on any such QPO. In the FB the power spectrum showed a somewhat less broad noise component (FWHM ~11 Hz) peaking near 6 Hz with a fractional rms of ~4% (2-30 keV). We compare our results with previous reports, and find that the fast timing behaviour changes not only with position in the Z, but also as a function of the position of the Z track in the hardness-intensity diagram. By comparing GX 349+2 with the other Z and atoll sources, we conclude that GX 349+2 differs from the Z sources in various aspects and shows similarities to the behaviour seen in the bright atoll sources, such as GX 13+1 and GX 3+1. We also searched for kilo-Hertz QPO, similar to those present in other Z sources. We only found weak evidence (2.6 sigma confidence) for a QPO near 1020 Hz with FWHM ~40 Hz and fractional rms of ~1%. We note that this frequency and fractional rms are consistent with those expected and observed in the lower NB/FB of the Z sources Sco X-1, GX 17+2 and Cyg X-2. | |
| dc.description | 8 pages, including 3 Postscript figures. Accepted by A&A Main Journal | |
| dc.identifier | https://arxiv.org/abs/astro-ph/9712311 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/9712311 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/11964 | |
| dc.subject | Astrophysics | |
| dc.title | GX 349+2 (Sco X-2): An odd-ball among the Z sources | |
| dc.type | text |