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Title: Chandra spectroscopy of MAXI J1305–704: Detection of an infalling black hole disk wind?

We report on a high-resolution Chandra/HETG X-ray spectrum of the transient X-ray binary MAXI J1305–704. A rich absorption complex is detected in the Fe L band, including density-sensitive lines from Fe XX, Fe XXI, and Fe XXII. Spectral analysis over three wavelength bands with a large grid of XSTAR photoionization models generally requires a gas density of n ≥ 10{sup 17} cm{sup –3}. Assuming a luminosity of L = 10{sup 37} erg s{sup –1}, fits to the 10-14 Å band constrain the absorbing gas to lie within r = (3.9 ± 0.7) × 10{sup 3} km from the central engine, or about r = 520 ± 90 (M/5 M {sub ☉}) r{sub g} , where r{sub g} = GM/c {sup 2}. At this small distance from the compact object, gas in stable orbits should have a gravitational redshift of z = v/c ≅ (3 ± 1) × 10{sup –3} (M/5 M {sub ☉}), and any tenuous inflowing gas should have a free-fall velocity of v/c ≅ (6 ± 1) × 10{sup –2} (M/5 M {sub ☉}){sup 1/2}. The best-fit single-zone photoionization models measure a redshift of v/c = (2.6-3.2) × 10{sup –3}. Models with two absorbing zones provide significantly improvedmore » fits, and the additional zone is measured to have a redshift of v/c = (4.6-4.9) × 10{sup –2} (models including two zones suggest slightly different radii and may point to lower densities). Thus, the observed shifts are broadly consistent with those expected at the photoionization radius. The absorption spectrum revealed in MAXI J1305–704 may be best explained in terms of a 'failed wind' like those predicted in some recent numerical simulations of black hole accretion flows. The robustness of the velocity shifts was explored through detailed simulations with the Chandra/MARX ray-tracing package and analysis of the zeroth-order ACIS-S3 spectrum. These tests are particularly important given the anomalously large angle between the source and the optical axis in this observation. The simulations and ACIS spectrum suggest that the shifts are not instrumental; however, strong caution is warranted. We discuss our results in the context of accretion flows in stellar-mass black holes and active galactic nuclei, as well as the potential role of failed winds in emerging connections between disk outflows and black hole state transitions.« less
Authors:
; ; ; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  3. NASA Goddard Space Flight Center, Code 662, Greedbelt, MD 20771 (United States)
  4. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom)
  5. Department of Physics, University of Nevada, Las Vegas, Las Vegas, NV 89154 (United States)
  6. Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States)
  7. Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201 (United States)
  8. Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
  9. Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom)
Publication Date:
OSTI Identifier:
22356668
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 788; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABSORPTION SPECTRA; ACCRETION DISKS; BLACK HOLES; COMPUTERIZED SIMULATION; DENSITY; DETECTION; GALAXY NUCLEI; LUMINOSITY; MASS; ORBITS; PHOTOIONIZATION; RED SHIFT; RESOLUTION; SPECTROSCOPY; TRANSIENTS; VELOCITY; WAVELENGTHS; X RADIATION; X-RAY SPECTRA