Simultaneous multi-band radio and X-ray observations of the galactic center magnetar SGR 1745–2900
- University of Virginia, Department of Astronomy, P. O. Box 400325 Charlottesville, VA 22904-4325 (United States)
- Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047, Cagliari (Italy)
- Istituto di Astrofisica Spaziale e Fisica Cosmica—Milano, INAF, via E. Bassini 15, I-20133, Milano (Italy)
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090-GE Amsterdam (Netherlands)
- Department of Physics and Astronomy, Amherst College, Amherst, MA 01002-5000 (United States)
- Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
- INAF–Osservatorio Astronomico di Roma, via Frascati 33, I-00040, Monteporzio Catone, Roma (Italy)
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,qui}/L{sub rot}≲1, an increase in the radio flux during the X-ray flux decay has not been observed thus far in other systems.
- OSTI ID:
- 22882868
- Journal Information:
- Astrophysical Journal, Vol. 808, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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