arXiv subjects

E. T. Harlaftis

Publications and source records attributed to E. T. Harlaftis.

22 records · Page 2Linked to original sources

arXiv1997

The 1996 Outburst of GRO J1655-40

During 1996 the soft-X-ray transient and superluminal jet source GRO J1655-40 was observed in outburst with a multiwavelength campaign including HST, RXTE, CGRO and ground based facilities. Here we focus on a key question raised by the observations: where and how does the outburst optical flux originate? Any model must not only fit the optical spectra, but must account for the observation that X-ray fluxes continued to rise slowly while the optical flux declined, contrary to predictions of standard models for the outburst of SXTs and dwarf novae.

astro-ph↗

arXiv1997

Spiral structure in the accretion disc of the binary IP Pegasi

We have found the first convincing evidence for spiral structure in the accretion disc of a close binary. The eclipsing dwarf nova binary IP Peg, observed during the end phase of a rise to outburst, shows strong Balmer and Helium emission lines in its spectra, with asymmetric double peaked velocity profiles produced in the accretion disc around the white dwarf. To reveal the two armed spiral on the accretion disc, we de-project the observed emission line profiles onto a Doppler coordinate frame, a technique known as Doppler tomography. The two armed spiral structure we see in the Doppler tomograms is expected to form when the disc becomes sufficiently large in outburst so that the tides induced by the secondary star can excite waves in the outer disc. Such spiral waves have been predicted in studies of tidal effects in discs and are fundamental in understanding the angular momentum budget of accretion discs.

astro-ph↗

arXiv1995

OY Car in Outburst: Balmer emission from the red star and the gas stream

We present observations of OY Car, obtained with the Anglo-Australian telescope, during a normal outburst in 1991. Two sinusoidal components are resolved in the Hbeta trailed spectra and we determine the location of the narrow component to be on the secondary star with a maximum contributed flux of ~2.5 per cent to the total flux. Imaging of the line distribution reveals that the other emission component is associated with the gas stream. This follows a velocity close to the ballistic one from the red star to a distance of ~0.5 R_L1 from the white dwarf. Then. its kinematics changes from 0.5-0.2 R_L1 (accretion disc) following velocities now closer to (but lower than) the keplerian velocities along the path of the gas stream. We finally dicsuss the implications of having observed simultaneously line emission from the gas stream and the red star during outburst.

astro-ph↗

arXiv1995

OY Car During Normal Outburst: Balmer Emission From The Red Star And The Gas Stream

We present observations of OY Car, obtained with the Anglo-Australian Telescope, during a normal outburst in August 1991. Two sinusoidal components are resolved in the H$β$ trailed spectra and we determine the location of the narrow component to be on the secondary star with a maximum contributed flux of ~2.5 per cent to the total flux. Imaging of the line distribution reveals that the other emission component is associated with the gas stream. This follows a velocity close to the ballistic one from the red star to a distance of ~0.5 R$_{L_{1}}$ from the white dwarf. This emission penetrates the accretion disc (from 0.5--0.1 R$_{L_{1}}$), with a velocity now closer (but lower) to the keplerian velocities along the path of the gas stream. We finally discuss the implications of having observed simultaneously line emission from the gas stream and the red star during outburst.

astro-ph↗