arXiv subjects

S. P. S. Eyres

Publications and source records attributed to S. P. S. Eyres.

58 records · Page 4Linked to original sources

arXiv2001

A search for radio emission from Galactic supersoft X-ray sources

We have made a deep search for radio emission from all the northern hemisphere supersoft X-ray sources using the VLA and MERLIN telescopes, at 5 and 8.4 GHz. Three previously undetected sources: T Pyx, V1974 Cygni and RX J0019.8+2156 were imaged in quiescence using the VLA in order to search for any persistent emission. No radio emission was detected in any of the VLA fields down to a typical 1 sigma RMS noise of 20 uJy/beam, however, 17 new point sources were detected in the fields with 5 GHz fluxes between 100 and 1500 uJy giving an average 100 uJy-source density of around 200 per square degree, comparable to what was found in the MERLIN HDF survey. The persistent source AG Draconis was observed by MERLIN to provide a confirmation of previous VLA observations and to investigate the source at a higher resolution. The core is resolved at the milliarcsec scale into two components which have a combined flux of around 1 mJy. It is possible that we are detecting nebulosity which is becoming resolved out by the higher MERLIN resolution. We have investigated possible causes of radio emission from a wind environment, both directly from the secondary star, and also as a consequence of the high X-ray luminosity from the white dwarf. There is an order of magnitude discrepancy between observed and modelled values which can be explained by the uncertainty in fundamental quantities within these systems.

astro-ph↗

arXiv2001

The symbiotic star CH Cygni. I. Non-thermal bipolar jets

VLA surface brightness and spectral index maps of the evolving extended emission of the triple symbiotic star CH Cygni are presented. These are derived from observations at 4.8, 8.4 and 14GHz between 1985 and 1999. The maps are dominated by thermal emission around the central bright peak of the nebula, but we also find unambiguous non-thermal emission associated with the extended regions. Our observations confirm that this is a jet. The central region has been associated with the stellar components through HST imaging. If the jets are due to ejection events at outburst, expansion velocities are consistent with those from other measurement methods. We propose that the non-thermal emission is caused by material ejected in the bipolar jets interacting with the circumstellar wind envelope. The resulting shocks lead to local enhancements in the magnetic field from the compact component of the order 3mG.

astro-ph↗

arXiv2001

The Infrared Evolution of Sakurai's Object

Infrared spectroscopy and photometry have revealed the remarkable evolution of Sakurai's Object from 1996 to the present. A cooling, carbon-rich photospheric spectrum was observable from 1996 to 1998. Considerable changes occured in 1998 as the continuum reddened due to absorption and emission by newly formed dust located outside the photosphere. In addition, a strong and broad helium 1.083 $μ$m P Cygni line developed, signifying the acceleration of an outer envelope of material to speeds as high as 1000 km s$^{-1}$. At the same time the photosphere of the central star remained quiescent. By 1999 the photosphere was virtually completely obscured by the dust and the helium emission line was the only detectable spectral feature remaining in the 1-5 $μ$m band. In 2000 emission by dust has become even more dominant, as the envelope continues to expand and cool and the helium line weakens.

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arXiv2001

The inner nebula and central binary of the symbiotic star HM Sge

We present contemporaneous HST WFPC2 and VLA observations of the symbiotic nova HM Sge. We identify a number of discreet features at spatial scales smaller than approximately 0.1 arcsec embedded in the extended nebula, with radio and optical emission well correlated in the inner 1 arcsec. For the first time we measure the positions of the binary components of a symbiotic star directly. We estimate the projected angular binary separation to be 40+/-9 milli-arcsec, with the binary axis at position angle 130+/-10 degrees. The latter is consistent with previous estimates made by indirect methods. The binary separation is consistent with a previous estimate of 50 au if the distance is 1250+/-280 pc. Temperature and density diagnostics show two distinct regions in the surrounding nebula, with a cool wedge to the south-west. An extinction map indicates the true interstellar extinction to be no more than E(B-V) = 0.35. This is consistent with a minimum distance of approximatelly 700 pc, but this would be reduced if there is a circumstellar contribution to the minimum in the extinction map. The extinction map also suggests a patchy dust distribution. We suggest that a southern concentration of dust and the south-west wedge are associated with the cool component wind. Alternatively, the southern dust concentration is the cause of the cool wedge, as it shields part of the nebula from the hot component radiation field.

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