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TOPIC: X1822-371

Blobrana

L

Posts: 131433

Date: Sep 4 18:32 2012

V691 Coronae Australis	Permalink

Title: A tomographic study of V691 CrA (X1822-371) Authors: Charith Peris, Saeqa Dil Vrtilek We present Doppler and modulation tomography of the low-mass X-ray binary V691 CrA with data obtained using the 6.5-m Magellan Baade telescope at the Las Campanas Observatory in 2010 and 2011. The disc and hotspot are observed in H\alpha and He II (\lambda 4686) in both years. A clear image of the disc is seen in He II (\lambda 5411) using the 2010 data. We present the first tomography of the absorption line He I (\lambda 5876) and detect absorption near the L_1 point of the donor star. We also present the first modulation tomography of the emission line H\alpha and detect emission from the secondary. The H\alpha double peaks are imbedded in a deep absorption trough confirming the presence of Balmer line absorbing material in the system. Our observations of H\alpha show absorption in a larger phase range than in H\beta which could be due to heating up of sprayed matter from the hotspot as it travels downstream. We also suggest possible occultation of the H\alpha absorbing spray by the disc bulge at certain phases. Read more (1063kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Jul 16 17:40 2012

X1822-371	Permalink

Title: Detailed study of the X-ray and Optical/UV orbital ephemeris of X1822-371 Authors: R. Iaria, T. Di Salvo, L. Burderi, A. D'Ai, A. Papitto, A. Riggio, N. R. Robba Recent studies of the optical/UV and X-ray ephemerides of X1822-371 have found some discrepancies in the value of the orbital period derivative. Because of the importance of this value in constraining the system evolution, we comprehensively analyse all the available optical/UV/X eclipse times of this source to investigate the origin of these discrepancies. We collected all previously published X-ray eclipse times from 1977 to 2008, to which we added the eclipse time observed by Suzaku in 2006. This point is very important to cover the time gap between the last RXTE eclipse time (taken in 2003) and the most recent Chandra eclipse time (taken in 2008). Similarly we collected the optical/UV eclipse arrival times covering the period from 1979 to 2006, adding a further eclipse time taken on 1978 and updating previous optical/UV ephemeris. We compared the X-ray and the optical/UV ephemeris, and finally derived a new ephemeris of the source by combining the eclipse arrival times in the X-ray and optical/UV bands. The X-ray eclipse time delays calculated with respect to a constant orbital period model display a clear parabolic trend, confirming that the orbital period of this source constantly increases at a rate of \dot{P}_{orb} =1.51(7) x 10^{-10} s/s. Combining the X-ray and the optical/UV data sets, we find that \dot{P}_{orb} =1.59(9) x 10^{-10} s/s, which is compatible with the X-ray orbital solution. We also investigate the possible presence of a delay of the optical/UV eclipse with respect to the X-ray eclipse, finding that this delay may not be constant in time. In particular, this variation is compatible with a sinusoidal modulation of the optical/UV eclipse arrival times with respect to the long-term parabolic trend. In this case, the optical/UV eclipse should lag the X-ray eclipse and the time-lag oscillate about an average value. Read more (110kb, PDF) __________________

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