V4641 Sgr: A candidate precessing microblazar
The X-ray spectrum of the Galactic X-ray binary V4641 Sgr in outburst has been found to exhibit a remarkably broad emission feature above 4 keV, with inferred equivalent widths up to 2 keV. Such a feature was first detected during the X-ray flaring activity associated with the giant outburst that th...
| Main Authors: | , , |
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| Format: | Journal Article |
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Oxford Academic
2014
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| Online Access: | http://hdl.handle.net/20.500.11937/52278 |
| _version_ | 1848758889731850240 |
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| author | Gallo, E. Plotkin, Richard Jonker, P. |
| author_facet | Gallo, E. Plotkin, Richard Jonker, P. |
| author_sort | Gallo, E. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | The X-ray spectrum of the Galactic X-ray binary V4641 Sgr in outburst has been found to exhibit a remarkably broad emission feature above 4 keV, with inferred equivalent widths up to 2 keV. Such a feature was first detected during the X-ray flaring activity associated with the giant outburst that the source experienced in 1999 September. The extraordinarily large equivalent width line was then ascribed to reflection/reprocessing of fluorescent Fe emission within an extended optically thick outflow enshrouding the binary system as a result of a shortlived, super-Eddington accretion episode. Making use of new and archival X-ray observations, we show here that a similar feature persists over four orders of magnitude in luminosity, down to Eddington ratios as low as log (LX/LEdd)~-4.5, where the existence of an optically thick envelope appears at odds with any viable accretion flow model. Possible interpretations for this highly unusual X-ray spectrum include a blend of Doppler-shifted/boosted Fe lines from unresolved X-ray jets (a la SS433), or, the first Galactic analogue of a blazar spectrum, where the >4 keV emission would correspond to the onset of the inverse Compton hump. This either requires a low-inclination angle of the jet with respect to the line of sight, in agreement with the estimates for the 1999 superluminal jet (ijet <10°). The fast variability of the feature, combined with the high orbital axis inclination (60° <iorb <71°), argue for a rapidly precessing accretion flow around V4641 Sgr, possibly leading to a transient microblazar behaviour. © 2013 The Authors. |
| first_indexed | 2025-11-14T09:51:10Z |
| format | Journal Article |
| id | curtin-20.500.11937-52278 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:51:10Z |
| publishDate | 2014 |
| publisher | Oxford Academic |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-522782017-09-13T15:48:31Z V4641 Sgr: A candidate precessing microblazar Gallo, E. Plotkin, Richard Jonker, P. The X-ray spectrum of the Galactic X-ray binary V4641 Sgr in outburst has been found to exhibit a remarkably broad emission feature above 4 keV, with inferred equivalent widths up to 2 keV. Such a feature was first detected during the X-ray flaring activity associated with the giant outburst that the source experienced in 1999 September. The extraordinarily large equivalent width line was then ascribed to reflection/reprocessing of fluorescent Fe emission within an extended optically thick outflow enshrouding the binary system as a result of a shortlived, super-Eddington accretion episode. Making use of new and archival X-ray observations, we show here that a similar feature persists over four orders of magnitude in luminosity, down to Eddington ratios as low as log (LX/LEdd)~-4.5, where the existence of an optically thick envelope appears at odds with any viable accretion flow model. Possible interpretations for this highly unusual X-ray spectrum include a blend of Doppler-shifted/boosted Fe lines from unresolved X-ray jets (a la SS433), or, the first Galactic analogue of a blazar spectrum, where the >4 keV emission would correspond to the onset of the inverse Compton hump. This either requires a low-inclination angle of the jet with respect to the line of sight, in agreement with the estimates for the 1999 superluminal jet (ijet <10°). The fast variability of the feature, combined with the high orbital axis inclination (60° <iorb <71°), argue for a rapidly precessing accretion flow around V4641 Sgr, possibly leading to a transient microblazar behaviour. © 2013 The Authors. 2014 Journal Article http://hdl.handle.net/20.500.11937/52278 10.1093/mnrasl/slt152 Oxford Academic fulltext |
| spellingShingle | Gallo, E. Plotkin, Richard Jonker, P. V4641 Sgr: A candidate precessing microblazar |
| title | V4641 Sgr: A candidate precessing microblazar |
| title_full | V4641 Sgr: A candidate precessing microblazar |
| title_fullStr | V4641 Sgr: A candidate precessing microblazar |
| title_full_unstemmed | V4641 Sgr: A candidate precessing microblazar |
| title_short | V4641 Sgr: A candidate precessing microblazar |
| title_sort | v4641 sgr: a candidate precessing microblazar |
| url | http://hdl.handle.net/20.500.11937/52278 |