IAU Circ., 8695, 2 (2006/March-0)
GONZALEZ-RIESTRA R., ORIO M. and LEIBOWITZ E.
Abstract (from CDS):
R. Gonzalez-Riestra, XMM-Newton Science Operation Centre, European Space Agency; M. Orio, National Institute of Astrophysics of Italy and University of Wisconsin; and E. Leibowitz, Tel Aviv University, write that RS Oph was observed with XMM-Newton on Feb. 26 for 400 minutes and on Mar. 10 for 197 minutes. At both times, prominent emission lines were observed with the RGS gratings, due to H-like and He-like transitions of N, O, Mg, Ne, Si, and Fe. The total flux was about 1.4 x 10**-10 erg/s in the first observation and about 1.1 x 10**-10 erg/s in the second. Some emission lines in the range 0.6-1.6 nm decreased in strength by the second observation, while other lines in the region 1.7-3.3 nm became much more prominent, especially O VII (1.897 nm) and N VIII (2.478 nm), due to a decrease of the column density of neutral hydrogen to a value not exceeding 3 x 10**21 cm**-2 on Mar. 10. The lines were blueshifted by 1100-1400 km/s in the first observation and only by a few hundred km/s in the second, and at both times, their full- width-at-half-maximum corresponded to at least 2000 km/s. Both EPIC-pn spectra showed also the Fe-K-alpha complex in emission, but it was significantly stronger in the February spectrum. During the second observation, after the first 2800 s, the EPIC-pn count-rate in the range 0.15-0.50 keV quadrupled in approximately 1700 s, then decreased by 40 percent in the following 1500 s and remained approximately constant until the end. During the rise and fall, the power spectrum shows a significant signal with a period of 35.685 s. The EPIC-pn count-rate in the range 1-10 keV had non- correlated variations by 10 percent and no coherent oscillations.
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