SIMULTANEOUS MULTI-BAND RADIO AND X-RAY OBSERVATIONS OF THE GALACTIC CENTER MAGNETAR SGR 1745–2900
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Author(s)
Pennucci, T. T.
Possenti, A.
Esposito, P.
Rea, N.
Haggard, D.
Burgay, M.
Zelati, F. Coti
Israel, G. L.
Minter, A.
Baganoff, Frederick K
Date Issued
July 2015
Journal
The Astrophysical Journal
Publisher
IOP Publishing
Citation
Pennucci, T. T., A. Possenti, P. Esposito, N. Rea, D. Haggard, F. K. Baganoff, M. Burgay, F. Coti Zelati, G. L. Israel, and A. Minter. “SIMULTANEOUS MULTI-BAND RADIO AND X-RAY OBSERVATIONS OF THE GALACTIC CENTER MAGNETAR SGR 1745–2900.” The Astrophysical Journal 808, no. 1 (July 20, 2015): 81. © 2015 The American Astronomical Society
Version
Final published version
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[subscript X,qui]/L[subscript rot] [< over ~] 1, an increase in the radio flux during the X-ray flux decay has not been observed thus far in other systems.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1088/0004-637X/808/1/81
