NICER follow-up of the Be X-ray pulsar Swift J1626.6-5156

W. Iwakiri*, M. Wolff, K. Pottschmidt, K. Gendreau, H. Negoro, M Nakajima, T. Mihara, C. Malacaria, Deepto Chakrabarty, G. K. Jaisawal

*Corresponding author for this work

Research output: Other contributionNet publication - Internet publicationResearch


A new X-ray outburst from the Be X-ray binary Swift J1626.6-5156 was recently detected by MAXI/GSC (ATel #14454). On 2021 March 11 16:40, NICER obtained a 2.75 ks exposure of the source. The results of the pulsation search show that there is a strong periodicity of 15.34 seconds. The 0.5 - 10 keV pulse profile has a sinusoidal shape with a 34% pulsed fraction. Since the detected pulse period is consistent with previous observations (e.g, ATel #678, #679), we confirm that this is a new outburst from Swift J1626.6-5156 after 15 years of quiescence. The NICER 0.5-10 keV spectrum can be fitted with an absorbed blackbody model (kT = 0.093±0.005 keV; hydrogen column density 1.08±0.08×1022 cm-2) plus a broken power-law continuum with pre and post photon indices 0.45(±0.09) and 1.27 (±0.07), respectively. The best-fit break energy is at 3.4(±0.1) keV. A cyclotron absorption line is possibly detected; the best-fit centroid energy is 9.1 (+0.3, -0.2) keV and the line width is 1.1(+0.3, -0.2) keV with an optical depth of 0.5(+0.3, -0.2). The X-ray flux in the 0.5-10 keV band is 3.18(±0.04)×10-10 erg cm-2 s-1. The obtained centroid energy of the cyclotron absorption line is consistent with that detected in the previous outburst (DeCesar et al. 2013, ApJ, 762, 61). However, since the energy range of NICER is limited to about 12 keV, we encourage follow-up observations in the higher energy range to reveal the information about the cyclotron resonance feature.

NICER is a 0.2-12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA.
Original languageEnglish
Publication date14 Mar 2021
Publication statusPublished - 14 Mar 2021
SeriesThe Astronomer's telegram
NumberATel #14457


  • X-ray
  • Transient,
  • Pulsar


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