A new perspective on GCRT J1745-3009
Context: Reports on a transient source about 1.25° south of the Galactic Centre motivated these follow-up observations with the WSRT and the reinvestigation of archival VLA data. The source GCRT J1745-3009 was detected during a 2002 Galactic Centre monitoring programme with the VLA at 92 cm by five...
| Main Authors: | , , , , , , |
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| Format: | Journal Article |
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EDP Sciences
2009
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| Online Access: | http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2009A%2526A...502..549SFUL http://hdl.handle.net/20.500.11937/31969 |
| _version_ | 1848753532140781568 |
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| author | Spreeuw, H. Scheers, B. Braun, R. Wijers, R. Miller-Jones, James Stappers, B. Fender, R. |
| author_facet | Spreeuw, H. Scheers, B. Braun, R. Wijers, R. Miller-Jones, James Stappers, B. Fender, R. |
| author_sort | Spreeuw, H. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Context: Reports on a transient source about 1.25° south of the Galactic Centre motivated these follow-up observations with the WSRT and the reinvestigation of archival VLA data. The source GCRT J1745-3009 was detected during a 2002 Galactic Centre monitoring programme with the VLA at 92 cm by five powerful 10-min bursts with a 77-min recurrence while apparently lacking any interburst emission.Aims: The WSRT observations were performed and archival VLA data reduced to detect GCRT J1745-3009 again at different epochs and frequencies, to constrain its distance, and to determine its nature. We attempted to extract a more accurate lightcurve from the discovery dataset of GCRT J1745-3009 to rule out some of the models that have been suggested. We also investigated the transient behaviour of a nearby source.Methods: The WSRT data were taken in the “maxi-short” configuration, using 10 s integrations, on 2005 March 24 at 92 cm and on 2005 May 14/15 at 21 cm. Five of the six VLA observations we reduced are the oldest of this field in this band.Results: GCRT J1745-3009 was not redetected. With the WSRT we reached an rms sensitivity of 0.21 mJy beam-1 at 21 cm and 3.7 mJy beam-1 at 92 cm. Reanalysis of the discovery observation data resulted in a more accurate and more complete lightcurve. The five bursts appear to have the same shape: a steep rise, a more gradual brightening, and a steep decay. We found variations in burst duration of order ?3%. We improved the accuracy of the recurrence period of the bursts by an order of magnitude: 77.012 ± 0.021 min. We found no evidence of aperiodicity. We derived a very steep spectral index: a=-6.5 ± 3.4. We improved the 5s upper limits for interburst emission and fractional circular polarisation to 31 mJy beam-1 and 8%, respectively. Any transient behaviour of a nearby source could not be established.Conclusions: Models that predict symmetric bursts can be ruled out, but rotating systems are favoured, because their periodicity is precise. Scattering constraints imply that GCRT J1745-3009 cannot be located far beyond the GC. If this source is an incoherent emitter and not moving at a relativistic velocity, it must be closer than 14 pc. |
| first_indexed | 2025-11-14T08:26:00Z |
| format | Journal Article |
| id | curtin-20.500.11937-31969 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T08:26:00Z |
| publishDate | 2009 |
| publisher | EDP Sciences |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-319692017-02-28T01:43:28Z A new perspective on GCRT J1745-3009 Spreeuw, H. Scheers, B. Braun, R. Wijers, R. Miller-Jones, James Stappers, B. Fender, R. stars: individual: GCRT J1745-3009 stars: binaries: close stars: neutron radio continuum: stars Context: Reports on a transient source about 1.25° south of the Galactic Centre motivated these follow-up observations with the WSRT and the reinvestigation of archival VLA data. The source GCRT J1745-3009 was detected during a 2002 Galactic Centre monitoring programme with the VLA at 92 cm by five powerful 10-min bursts with a 77-min recurrence while apparently lacking any interburst emission.Aims: The WSRT observations were performed and archival VLA data reduced to detect GCRT J1745-3009 again at different epochs and frequencies, to constrain its distance, and to determine its nature. We attempted to extract a more accurate lightcurve from the discovery dataset of GCRT J1745-3009 to rule out some of the models that have been suggested. We also investigated the transient behaviour of a nearby source.Methods: The WSRT data were taken in the “maxi-short” configuration, using 10 s integrations, on 2005 March 24 at 92 cm and on 2005 May 14/15 at 21 cm. Five of the six VLA observations we reduced are the oldest of this field in this band.Results: GCRT J1745-3009 was not redetected. With the WSRT we reached an rms sensitivity of 0.21 mJy beam-1 at 21 cm and 3.7 mJy beam-1 at 92 cm. Reanalysis of the discovery observation data resulted in a more accurate and more complete lightcurve. The five bursts appear to have the same shape: a steep rise, a more gradual brightening, and a steep decay. We found variations in burst duration of order ?3%. We improved the accuracy of the recurrence period of the bursts by an order of magnitude: 77.012 ± 0.021 min. We found no evidence of aperiodicity. We derived a very steep spectral index: a=-6.5 ± 3.4. We improved the 5s upper limits for interburst emission and fractional circular polarisation to 31 mJy beam-1 and 8%, respectively. Any transient behaviour of a nearby source could not be established.Conclusions: Models that predict symmetric bursts can be ruled out, but rotating systems are favoured, because their periodicity is precise. Scattering constraints imply that GCRT J1745-3009 cannot be located far beyond the GC. If this source is an incoherent emitter and not moving at a relativistic velocity, it must be closer than 14 pc. 2009 Journal Article http://hdl.handle.net/20.500.11937/31969 http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2009A%2526A...502..549SFUL EDP Sciences restricted |
| spellingShingle | stars: individual: GCRT J1745-3009 stars: binaries: close stars: neutron radio continuum: stars Spreeuw, H. Scheers, B. Braun, R. Wijers, R. Miller-Jones, James Stappers, B. Fender, R. A new perspective on GCRT J1745-3009 |
| title | A new perspective on GCRT J1745-3009 |
| title_full | A new perspective on GCRT J1745-3009 |
| title_fullStr | A new perspective on GCRT J1745-3009 |
| title_full_unstemmed | A new perspective on GCRT J1745-3009 |
| title_short | A new perspective on GCRT J1745-3009 |
| title_sort | new perspective on gcrt j1745-3009 |
| topic | stars: individual: GCRT J1745-3009 stars: binaries: close stars: neutron radio continuum: stars |
| url | http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2009A%2526A...502..549SFUL http://hdl.handle.net/20.500.11937/31969 |