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http://hdl.handle.net/20.500.12386/23635
Title: | Simultaneous Multi-band Radio and X-Ray Observations of the Galactic Center Magnetar SGR 1745-2900 | Authors: | Pennucci, T. T. POSSENTI, ANDREA Esposito, P. Rea, N. Haggard, D. Baganoff, F. K. BURGAY, MARTA Coti Zelati, F. ISRAEL, Gian Luca Minter, A. |
Issue Date: | 2015 | Journal: | THE ASTROPHYSICAL JOURNAL | Number: | 808 | Issue: | 1 | First Page: | 81 | Abstract: | We report on multi-frequency, wideband radio observations of the Galactic Center magnetar (SGR 1745-2900) with the Green Bank Telescope for ̃100 days immediately following its initial X-ray outburst in 2013 April. We made multiple simultaneous observations at 1.5, 2.0, and 8.9 GHz, allowing us to examine the magnetar's flux evolution, radio spectrum, and interstellar medium parameters (such as the dispersion measure (DM), the scattering timescale, and its index). During two epochs, we have simultaneous observations from the Chandra X-ray Observatory, which permitted the absolute alignment of the radio and X-ray profiles. As with the two other radio magnetars with published alignments, the radio profile lies within the broad peak of the X-ray profile, preceding the X-ray profile maximum by ̃0.2 rotations. We also find that the radio spectral index γ is significantly negative between ̃2 and 9 GHz; during the final ̃30 days of our observations γ ̃ -1.4, which is typical of canonical pulsars. The radio flux has not decreased during this outburst, whereas the long-term trends in the other radio magnetars show concomitant fading of the radio and X-ray fluxes. Finally, our wideband measurements of the DMs taken in adjacent frequency bands in tandem are stochastically inconsistent with one another. Based on recent theoretical predictions, we consider the possibility that the DM is frequency-dependent. Despite having several properties in common with the other radio magnetars, such as {L}<SUB>{{X</SUB>},{qui}}/{L}<SUB>{rot</SUB>}≲ 1, an increase in the radio flux during the X-ray flux decay has not been observed thus far in other systems. | Acknowledgments: | The authors would like to thank S. Ransom and P. Demorest for useful discussions and comments, as well as A. Bilous for significant contributions and a review of the manuscript. T. T. P. would also like to acknowledge the hospitality of the astronomers at the Osservatorio Astronomico di Cagliari, where this paper began. T. T. P. is supported in part by a National Science Foundation PIRE Grant (0968296) through NANOGrav and is a graduate student at the National Radio Astronomy Observatory (NRAO). The NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. P. E. acknowledges a Fulbright Research Scholar grant administered by the US–Italy Fulbright Commission and is grateful to the Harvard–Smithsonian Center for Astrophysics for hosting him during his Fulbright exchange. The Fulbright Scholar Program is sponsored by the US. Department of State and administered by CIES, a division of IIE. D. H. acknowledges support from Chandra X-ray Observatory Award Number GO3-14121X, operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060, and also by NASA Swift grant NNX14AC30G. N. R. and F. C. Z. are supported by an NWO Vidi Grant (PI: N. Rea) and by the European COST Action MP1304 (NewCOMPSTAR). N. R. acknowledges support by grants AYA2012-39303 and SGR2014-1073. Facilities: CXO (ACIS) , GBT (GUPPI) | URI: | http://hdl.handle.net/20.500.12386/23635 | URL: | https://iopscience.iop.org/article/10.1088/0004-637X/808/1/81 https://arxiv.org/pdf/1505.00836.pdf |
ISSN: | 0004-637X | DOI: | 10.1088/0004-637X/808/1/81 | Bibcode ADS: | 2015ApJ...808...81P | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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Pennucci_2015_ApJ_808_81.pdf | PDF editoriale | 1.85 MB | Adobe PDF | View/Open |
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