NuSTAR Observations of GS 1826-238 in the Extended Soft State
We report on the first focused NuSTAR observations of the neutron star low mass X-ray binary GS 1826-238, the “Clocked Burster,” since the extended soft state began in 2014. Throughout this day-long observation, we see spectral variability that is consistent with the “banana” branch of atoll LMXBs....
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/addf3f |
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| author | B. W. Grefenstette M. C. Brumback D. J. K. Buisson R. M. Ludlam G Mastroserio S. N. Pike J. A. Tomsick S. B. Yun |
| author_facet | B. W. Grefenstette M. C. Brumback D. J. K. Buisson R. M. Ludlam G Mastroserio S. N. Pike J. A. Tomsick S. B. Yun |
| author_sort | B. W. Grefenstette |
| collection | DOAJ |
| description | We report on the first focused NuSTAR observations of the neutron star low mass X-ray binary GS 1826-238, the “Clocked Burster,” since the extended soft state began in 2014. Throughout this day-long observation, we see spectral variability that is consistent with the “banana” branch of atoll LMXBs. The NuSTAR hard X-ray spectrum is consistent with that seen during the initial soft-state excursion in 2014 and is modeled as a double Comptonized plasma: one with low temperature and high optical depth, the other with high temperature and low optical depth. The spectral variations that we see in this source are mostly consistent with variations in the optical depth of the hot component, though the total flux from the source remains nearly constant. A single Type I X-ray burst is seen during this observation, which has a short main peak (timescales of seconds) followed by an extended tail of emission. The shape of this burst is not consistent with a PRE and provide diagnostic information on the regions of the NS surface supplying the fuel for the thermonuclear reaction. |
| format | Article |
| id | doaj-art-76bd3de995c144a69c9e40000e7cfdf4 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-76bd3de995c144a69c9e40000e7cfdf42025-08-20T03:33:14ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01987218010.3847/1538-4357/addf3fNuSTAR Observations of GS 1826-238 in the Extended Soft StateB. W. Grefenstette0https://orcid.org/0000-0002-1984-2932M. C. Brumback1https://orcid.org/0000-0002-4024-6967D. J. K. Buisson2R. M. Ludlam3https://orcid.org/0000-0002-8961-939XG Mastroserio4https://orcid.org/0000-0003-4216-7936S. N. Pike5https://orcid.org/0000-0002-8403-0041J. A. Tomsick6https://orcid.org/0000-0001-5506-9855S. B. Yun7Cahill Center for Astronomy and Astrophysics, California Institute of Technology , Pasadena, CA 91125, USA ; bwgref@srl.caltech.eduDepartment of Physics, Middlebury College , Middlebury, VT 05753, USAIndependentDepartment of Physics & Astronomy, Wayne State University , 666 West Hancock Street, Detroit, MI 48201, USAINAF—Osservatorio Astronomico di Cagliari , via della Scienza 5, I-09047 Selargius (CA), ItalyCenter for Astrophysics and Space Sciences, University of California , San Diego, CA 92093, USASpace Sciences Laboratory, 7 Gauss Way, University of California , Berkeley, CA 94720-7450, USACahill Center for Astronomy and Astrophysics, California Institute of Technology , Pasadena, CA 91125, USA ; bwgref@srl.caltech.eduWe report on the first focused NuSTAR observations of the neutron star low mass X-ray binary GS 1826-238, the “Clocked Burster,” since the extended soft state began in 2014. Throughout this day-long observation, we see spectral variability that is consistent with the “banana” branch of atoll LMXBs. The NuSTAR hard X-ray spectrum is consistent with that seen during the initial soft-state excursion in 2014 and is modeled as a double Comptonized plasma: one with low temperature and high optical depth, the other with high temperature and low optical depth. The spectral variations that we see in this source are mostly consistent with variations in the optical depth of the hot component, though the total flux from the source remains nearly constant. A single Type I X-ray burst is seen during this observation, which has a short main peak (timescales of seconds) followed by an extended tail of emission. The shape of this burst is not consistent with a PRE and provide diagnostic information on the regions of the NS surface supplying the fuel for the thermonuclear reaction.https://doi.org/10.3847/1538-4357/addf3fX-ray bursts |
| spellingShingle | B. W. Grefenstette M. C. Brumback D. J. K. Buisson R. M. Ludlam G Mastroserio S. N. Pike J. A. Tomsick S. B. Yun NuSTAR Observations of GS 1826-238 in the Extended Soft State The Astrophysical Journal X-ray bursts |
| title | NuSTAR Observations of GS 1826-238 in the Extended Soft State |
| title_full | NuSTAR Observations of GS 1826-238 in the Extended Soft State |
| title_fullStr | NuSTAR Observations of GS 1826-238 in the Extended Soft State |
| title_full_unstemmed | NuSTAR Observations of GS 1826-238 in the Extended Soft State |
| title_short | NuSTAR Observations of GS 1826-238 in the Extended Soft State |
| title_sort | nustar observations of gs 1826 238 in the extended soft state |
| topic | X-ray bursts |
| url | https://doi.org/10.3847/1538-4357/addf3f |
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