Open AccessEpisodic absorption in the outflow of the old nova V603 Aquilae
Author(s) -
Prinja Raman K.,
Knigge Christian,
Ringwald F. A.,
Wade Richard A.
Publication year - 2000
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 - 10.1046/j.1365-8711.2000.03702.x
Subject(s) - physics , astrophysics , outflow , accretion (finance) , absorption (acoustics) , space telescope imaging spectrograph , ultraviolet , spectrograph , flare , astronomy , spectral line , stars , hubble space telescope , optics , meteorology
We report on the time‐dependent behaviour of ultraviolet spectral lines in Hubble Space Telescope Goddard High‐Resolution Spectrograph data of the classical nova V603 Aql. In particular, episodic blueshifted absorption (extending to ∼−2500 km s −1 ) is present, with a variability time‐scale down to ∼1 min. The data provide a rare opportunity to study the rapid evolution of absorption structures that may be associated with accretion‐disc winds in cataclysmic variables. At least three absorption events are recorded (at blueward velocities only) over ∼5 h, each lasting ∼10–15 min. The derived velocity, acceleration and optical depth properties provide an empirical picture of stochastically variable structures in the outflow, with no evidence for short‐term (less than ∼1 h) cyclic or modulated behaviour in the overall absorption properties. In contrast, the emission components of the ultraviolet resonance lines are very stable in velocity and strength in this low‐inclination system. On at least two occasions there is an intriguing short‐term ‘flare’ in the ultraviolet continuum flux (of up to ∼40 per cent). Though there is no clear one‐to‐one relation in these data between the continuum fluctuations and the occurrence of the absorption events, the time‐scales for the two variable phenomena are essentially the same. The irregular absorption episodes in the ultraviolet data of V603 Aql presently defy a clear physical interpretation. Their overall characteristics are discussed in the context of instabilities in radiation‐pressure‐driven disc winds.