Open AccessThe 2003 radio outburst of a new X‐ray transient: XTE J1720−318
Author(s) -
Brocksopp C.,
Corbel S.,
Fender R. P.,
Rupen M.,
Sault R.,
Tingay S. J.,
Hannikainen D.,
O'Brien K.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08427.x
Subject(s) - physics , astrophysics , light curve , context (archaeology) , telescope , accretion (finance) , black hole (networking) , astronomy , spectral line , emission spectrum , glitch , radio telescope , optics , paleontology , computer network , routing protocol , routing (electronic design automation) , detector , computer science , biology , link state routing protocol
We present radio observations of the black hole X‐ray transient XTE J1720−318, which was discovered in 2003 January as it entered an outburst. We analyse the radio data in the context of the X‐ray outburst and the broad‐band spectrum. An unresolved radio source was detected during the rising phase, reaching a peak of nearly 5 mJy approximately coincident with the peak of the X‐ray light curve. A study of the spectral indices suggests that at least two ejection events took place, with the radio‐emitting material expanding and becoming optically thin as it faded. The broad‐band spectra suggested that the accretion disc dominated the emission, as expected for a source in a soft state. The radio emission decayed to below the sensitivity of the telescopes for ∼6 weeks but switched on again during the transition of the X‐ray source to the low/hard state. At least one ‘glitch’ was superimposed on the otherwise exponential decay of the X‐ray light curve, which was reminiscent of the multiple jet ejections of XTE J1859+226. We also present a K s ‐band image of XTE J1720−318 and its surrounding field taken with the Very Large Telescope.