VARIABLE HARD-X-RAY EMISSION from the CANDIDATE ACCRETING BLACK HOLE in DWARF GALAXY HENIZE 2-10

Thomas J. Whalen, Ryan C. Hickox, Amy E. Reines, Jenny E. Greene, Gregory R. Sivakoff, Kelsey E. Johnson, David M. Alexander, Andy D. Goulding

Research output: Contribution to journalArticle

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Abstract

We present an analysis of the X-ray spectrum and long-term variability of the nearby dwarf starburst galaxy Henize 2-10. Recent observations suggest that this galaxy hosts an actively accreting black hole (BH) with mass ∼106 . The presence of an active galactic nucleus (AGN) in a low-mass starburst galaxy marks a new environment for AGNs, with implications for the processes by which "seed" BHs may form in the early universe. In this paper, we analyze four epochs of X-ray observations of Henize 2-10, to characterize the long-term behavior of its hard nuclear emission. We analyze observations with Chandra from 2001 and XMM-Newton from 2004 and 2011, as well as an earlier, less sensitive observation with ASCA from 1997. Based on a detailed analysis of the source and background, we find that the hard (2-10 keV) flux of the putative AGN has decreased by approximately an order of magnitude between the 2001 Chandra observation and exposures with XMM-Newton in 2004 and 2011. The observed variability confirms that the emission is due to a single source. It is unlikely that the variable flux is due to a supernova or ultraluminous X-ray source, based on the observed long-term behavior of the X-ray and radio emission, while the observed X-ray variability is consistent with the behavior of well-studied AGNs.

Original languageEnglish (US)
Article number37
JournalAstrophysical Journal
Volume806
Issue number1
DOIs
StatePublished - Jun 10 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • X-rays: galaxies
  • galaxies: active
  • galaxies: dwarf
  • galaxies: evolution
  • galaxies: individual (Henize 210)

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    Whalen, T. J., Hickox, R. C., Reines, A. E., Greene, J. E., Sivakoff, G. R., Johnson, K. E., Alexander, D. M., & Goulding, A. D. (2015). VARIABLE HARD-X-RAY EMISSION from the CANDIDATE ACCRETING BLACK HOLE in DWARF GALAXY HENIZE 2-10. Astrophysical Journal, 806(1), [37]. https://doi.org/10.1088/0004-637X/806/1/37