NICER Observes the Effects of an X-Ray Burst on the Accretion Environment in Aql X-1

L. Keek, Z. Arzoumanian, P. Bult, E. M. Cackett, D. Chakrabarty, J. Chenevez, A. C. Fabian, K. C. Gendreau, S. Guillot, T. Güver, J. Homan, G. K. Jaisawal, F. K. Lamb, R. M. Ludlam, S. Mahmoodifar, C. B. Markwardt, J. M. Miller, G. Prigozhin, Y. Soong, T. E. StrohmayerM. T. Wolff

Research output: Contribution to journalArticlepeer-review


Accretion disks around neutron stars regularly undergo sudden strong irradiation by Type-I X-ray bursts powered by unstable thermonuclear burning on the stellar surface. We investigate the impact on the disk during one of the first X-ray burst observations with the Neutron Star Interior Composition Explorer (NICER) on the International Space Station. The burst is seen from Aql X-1 during the hard spectral state. In addition to thermal emission from the neutron star, the burst spectrum exhibits an excess of soft X-ray photons below 1 keV, where NICER's sensitivity peaks. We interpret the excess as a combination of reprocessing by the strongly photoionized disk and enhancement of the pre-burst persistent flux, possibly due to Poynting-Robertson drag or coronal reprocessing. This is the first such detection for a short sub-Eddington burst. As these bursts are observed frequently, NICER will be able to study how X-ray bursts affect the disk and corona for a range of accreting neutron star systems and disk states.

Original languageEnglish (US)
Article numberL4
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Mar 1 2018


  • accretion, accretion disks
  • stars: individual (Aql X-1)
  • stars: neutron
  • X-rays: binaries
  • X-rays: bursts

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'NICER Observes the Effects of an X-Ray Burst on the Accretion Environment in Aql X-1'. Together they form a unique fingerprint.

Cite this