The intriguing nature of the high-energy gamma ray source XSS J12270-4859
Context. The nature of the hard X-ray source XSS J12270-4859 is still unclear. It was claimed to be a possible magnetic cataclysmic variable of the Intermediate Polar type from its optical spectrum and a possible 860s X-ray periodicity in RXTE data. However, recent observations do not support the la...
| Authors: | ; ; ; ; ; ; ; ; ; |
|---|---|
| Format: | Article |
| Status: | Published version |
| Publication date: | 2010 |
| Country: | Argentina |
| Institution: | UNLP |
| Repository: | SEDICI (UNLP) |
| Language: | English |
| OAI Identifier: | oai:sedici.unlp.edu.ar:10915/82480 |
| Online Access: | http://sedici.unlp.edu.ar/handle/10915/82480 |
| Access Level: | Open access |
| Keyword: | Astronomía Binaries: close Stars: individual: 1FGLJ1227.9-4852 Stars: individual: XSS J12270-4859 X-rays: binaries |
| _version_ | 1878403022593196033 |
|---|---|
| author | Martino, D. de |
| author2 | Falanga, M. Bonnet-Bidaud, J.-M. Belloni, T. Mouchet, M. Masetti, N. Andruchow, Ileana Cellone, Sergio Mukai, K. Matt, G. |
| author2_role | author author author author author author author author author |
| author_browse | Andruchow, Ileana Belloni, T. Bonnet-Bidaud, J.-M. Cellone, Sergio Falanga, M. Martino, D. de Masetti, N. Matt, G. Mouchet, M. Mukai, K. |
| author_facet | Martino, D. de Falanga, M. Bonnet-Bidaud, J.-M. Belloni, T. Mouchet, M. Masetti, N. Andruchow, Ileana Cellone, Sergio Mukai, K. Matt, G. |
| author_role | author |
| collection | SEDICI (UNLP) |
| description | Context. The nature of the hard X-ray source XSS J12270-4859 is still unclear. It was claimed to be a possible magnetic cataclysmic variable of the Intermediate Polar type from its optical spectrum and a possible 860s X-ray periodicity in RXTE data. However, recent observations do not support the latter variability, leaving this X-ray source still unclassified. Aims. To investigate its nature we present a broad-band X-ray and gamma ray study of this source based on a recent XMM-Newton observation and archival INTEGRAL and RXTE data. Using the Fermi/LAT 1-year point source catalogue, we tentatively associate XSS J12270-4859 with 1FGL J1227.9-4852, a source of high-energy gamma rays with emission up to 10 GeV. We further complement the study with UV photometry from XMM-Newton and ground-based optical and near-IR photometry. Methods. We have analysed both timing and spectral properties in the gamma rays, X-rays, UV and optical/near-IR bands of XSS J12270-4859. Results. The X-ray emission is highly variable, showing flares and intensity dips. The flares consist of flare-dip pairs. Flares are detected in both X-rays and the UV range, while the subsequent dips are present only in the X-ray band. Further aperiodic dipping behaviour is observed during X-ray quiescence, but not in the UV. The broad-band 0.2-100 keV X-ray/soft gamma ray spectrum is featureless and well described by a power law model with Γ = 1.7. The high-energy spectrum from 100 MeV to 10 GeV is represented by a power law index of 2.45. The luminosity ratio between 0.1-100 GeV and 0.2-100 keV is ∼0.8, indicating that the GeV emission is a significant component of the total energy output. Furthermore, the X-ray spectrum does not greatly change during flares, quiescence and the dips seen in quiescence. The X-ray spectrum however hardens during the post-flare dips, where a partial covering absorber is also required to fit the spectrum. Optical photometry acquired at different epochs reveals a period of 4.32 hr that could be ascribed to the binary orbital period. Near-IR, possibly ellipsoidal, variations are detected. Large amplitude variability on shorter (tens mins) timescales is found to be non-periodic. Conclusions. The observed variability at all wavelengths together with the spectral characteristics strongly favour a low-mass atypical low-luminosity X-ray binary and are against a magnetic cataclysmic variable nature. The association with a Fermi/LAT high-energy gamma ray source further strengths this interpretation. |
| eu_rights_str_mv | openAccess |
| format | article |
| id | AR_2ec4abc2e094e25d892c67d6e34fa0b7 |
| institution | UNLP |
| instname_str | Universidad Nacional de La Plata |
| language | eng |
| network_acronym_str | AR |
| network_name_str | Argentina |
| oai_identifier_str | oai:sedici.unlp.edu.ar:10915/82480 |
| publishDate | 2010 |
| publishDateSort | 2010 |
| reponame_str | SEDICI (UNLP) |
| spelling | The intriguing nature of the high-energy gamma ray source XSS J12270-4859 Martino, D. de Falanga, M. Bonnet-Bidaud, J.-M. Belloni, T. Mouchet, M. Masetti, N. Andruchow, Ileana Cellone, Sergio Mukai, K. Matt, G. Astronomía Binaries: close Stars: individual: 1FGLJ1227.9-4852 Stars: individual: XSS J12270-4859 X-rays: binaries Context. The nature of the hard X-ray source XSS J12270-4859 is still unclear. It was claimed to be a possible magnetic cataclysmic variable of the Intermediate Polar type from its optical spectrum and a possible 860s X-ray periodicity in RXTE data. However, recent observations do not support the latter variability, leaving this X-ray source still unclassified. Aims. To investigate its nature we present a broad-band X-ray and gamma ray study of this source based on a recent XMM-Newton observation and archival INTEGRAL and RXTE data. Using the Fermi/LAT 1-year point source catalogue, we tentatively associate XSS J12270-4859 with 1FGL J1227.9-4852, a source of high-energy gamma rays with emission up to 10 GeV. We further complement the study with UV photometry from XMM-Newton and ground-based optical and near-IR photometry. Methods. We have analysed both timing and spectral properties in the gamma rays, X-rays, UV and optical/near-IR bands of XSS J12270-4859. Results. The X-ray emission is highly variable, showing flares and intensity dips. The flares consist of flare-dip pairs. Flares are detected in both X-rays and the UV range, while the subsequent dips are present only in the X-ray band. Further aperiodic dipping behaviour is observed during X-ray quiescence, but not in the UV. The broad-band 0.2-100 keV X-ray/soft gamma ray spectrum is featureless and well described by a power law model with Γ = 1.7. The high-energy spectrum from 100 MeV to 10 GeV is represented by a power law index of 2.45. The luminosity ratio between 0.1-100 GeV and 0.2-100 keV is ∼0.8, indicating that the GeV emission is a significant component of the total energy output. Furthermore, the X-ray spectrum does not greatly change during flares, quiescence and the dips seen in quiescence. The X-ray spectrum however hardens during the post-flare dips, where a partial covering absorber is also required to fit the spectrum. Optical photometry acquired at different epochs reveals a period of 4.32 hr that could be ascribed to the binary orbital period. Near-IR, possibly ellipsoidal, variations are detected. Large amplitude variability on shorter (tens mins) timescales is found to be non-periodic. Conclusions. The observed variability at all wavelengths together with the spectral characteristics strongly favour a low-mass atypical low-luminosity X-ray binary and are against a magnetic cataclysmic variable nature. The association with a Fermi/LAT high-energy gamma ray source further strengths this interpretation. Instituto de Astrofísica de La Plata Facultad de Ciencias Astronómicas y Geofísicas http://sedici.unlp.edu.ar/handle/10915/82480 |
| spellingShingle | The intriguing nature of the high-energy gamma ray source XSS J12270-4859 Martino, D. de Astronomía Binaries: close Stars: individual: 1FGLJ1227.9-4852 Stars: individual: XSS J12270-4859 X-rays: binaries |
| status_str | publishedVersion |
| title | The intriguing nature of the high-energy gamma ray source XSS J12270-4859 |
| title_full | The intriguing nature of the high-energy gamma ray source XSS J12270-4859 |
| title_fullStr | The intriguing nature of the high-energy gamma ray source XSS J12270-4859 |
| title_full_unstemmed | The intriguing nature of the high-energy gamma ray source XSS J12270-4859 |
| title_short | The intriguing nature of the high-energy gamma ray source XSS J12270-4859 |
| title_sort | The intriguing nature of the high-energy gamma ray source XSS J12270-4859 |
| topic | Astronomía Binaries: close Stars: individual: 1FGLJ1227.9-4852 Stars: individual: XSS J12270-4859 X-rays: binaries |
| topic_facet | Astronomía Binaries: close Stars: individual: 1FGLJ1227.9-4852 Stars: individual: XSS J12270-4859 X-rays: binaries |
| url | http://sedici.unlp.edu.ar/handle/10915/82480 |