Chandra Spectroscopy of MAXI J1305-704: Detection of an Infalling Black Hole Disk Wind?

TL;DR

This study uses Chandra X-ray spectroscopy to analyze the accretion disk wind in the black hole candidate MAXI J1305-704, revealing evidence of an infalling wind possibly representing a 'failed wind' scenario.

Contribution

First detection of a red-shifted disk wind in MAXI J1305-704, suggesting infalling material and providing insights into accretion flow dynamics and failed wind phenomena.

Findings

Detected density-sensitive Fe L absorption lines.

Measured red-shifts consistent with infalling gas.

Supported the 'failed wind' hypothesis in black hole accretion.

Abstract

We report on a Chandra/HETG X-ray spectrum of the black hole candidate MAXI J1305-704. A rich absorption complex is detected in the Fe L band, including density-sensitive lines from Fe XX, XXI, and XXII. Spectral analysis over three bands with photoionization models generally requires a gas density of n > 1 E+17 cm^-3. Assuming a luminosity of L = 1 E+37 erg/s, fits to the 10-14 A band constrain the absorbing gas to lie within r = 3.9(7) E+3 km from the central engine, or about r = 520 +/- 90 (M/5 Msun) r_g, where r_g = GM/c^2. At this distance from the compact object, gas in Keplerian orbits should have a gravitational red-shift of z = v/c ~ 3 +/- 1 E-3 (M/5 Msun), and any tenuous inflowing gas should have a free-fall velocity of v/c ~ 6 +/- 1 E-2 (M/5 Msun)^1/2. The best-fit single-zone photoionization models measure a red-shift of v/c = 2.6-3.2 E-3. Models with two zones provide significantly improved fits; the additional zone is measured to have a red-shift of v/c =4.6-4.9 E-2 (models including two zones suggest slightly different radii and may point to lower densities). Thus, the shifts are broadly consistent with the photoionization radius. The results may be explained in terms of a "failed wind" like those predicted in some numerical simulations. We discuss our results in the context of accretion flows across the mass scale, and the potential role of failed winds in black hole state transitions.