A SEYFERT-2-LIKE SPECTRUM IN THE HIGH-MASS X-RAY BINARY MICROQUASAR V4641 SGR

Abstract

We present an analysis of three archival Chandra observations of the black\nhole V4641 Sgr, performed during a decline into quiescence. The last two\nobservations in the sequence can be modeled with a simple power-law. The first\nspectrum, however, is remarkably similar to spectra observed in Seyfert-2\nactive galactic nuclei, which arise through a combination of obscuration and\nreflection from distant material. This spectrum of V4641 Sgr can be fit\nextremely well with a model including partial-covering absorption and distant\nreflection. This model recovers a Gamma = 2 power-law incident spectrum,\ntypical of black holes at low Eddington fractions. The implied geometry is\nplausible in a high-mass X-ray binary like V4641 Sgr, and may be as compelling\nas explanations invoking Doppler-split line pairs in a jet, and/or unusual\nComptonization. We discuss potential implications and means of testing these\nmodels.\n