Browsing by Author "An, H."

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    NuSTAR OBSERVATIONS OF MAGNETAR 1E 1048.1-5937
    (2016) Yang, C.; Archibald, R. F.; Vogel, J. K.; An, H.; Kaspi, V. M.; Guillot, S.; Beloborodov, A. M.; Pivovaroff, M.
    We report on simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR) and XMM-Newton observations of the magnetar 1E. 1048.1-5937, along with Rossi X-ray Timing Explorer (RXTE) data for the same source. The NuSTAR data provide a clear detection of this magnetar's persistent emission up to 20 keV. We detect a previously unreported small secondary peak in the average pulse profile in the 7-10 keV band, which grows to an amplitude comparable to that of the main peak in the 10-20 keV band. We show using RXTE data that this secondary peak is likely transient. We find that the pulsed fraction increases with energy from a value of similar to 0.55 at similar to 2. keV to a value of similar to 0.75 near 8. keV but shows evidence of decreasing at higher energies. After filtering out multiple bright X-ray bursts during the observation, we find that the phase-averaged spectrum from combined NuSTAR and XMM data is well described by an absorbed double blackbody plus power-law model, with no evidence for the spectral turn-up near similar to 10. keV as has been seen in some other magnetars. Our data allow us to rule out a spectral turn-up similar to those seen in magnetars 4U 0142+61 and 1E 2259+586 of Delta Gamma greater than or similar to 2, where Delta Gamma is the difference between the soft-band and hard-band photon indexes. The lack of spectral turn-up is consistent with what has been observed from an active subset of magnetars given previously reported trends suggesting that the degree of spectral turn-up is correlated with spin-down rate and/or spin-inferred magnetic field.
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    The Norma Arm Region Chandra Survey Catalog: X-ray populations in the spiral arms
    (2014) Fornasini, F.; Tomsick, J.; Bodaghee, A.; Krivonos, R.; An, H.; Rahoui, F.; Gotthelf, E.; Bauer, Franz Erik; Stern, D.