The Onset of a Compton-thick Wind in GX 13+1

Abstract The X-ray Imaging and Spectroscopy Mission (XRISM) recently reported the discovery of a recurrent Compton-thick accretion disk wind from the neutron star X-ray binary GX 13+1. Many earlier observations have revealed multicomponent disk winds from this system; the wind seen by XRISM was similar but featured a column density 1 order of magnitude higher than previously reported. In this Letter, we report on Chandra High Energy Transmission Grating Spectrometer observations taken in the days prior to the XRISM observation that reveal the evolution of the Compton-thick wind. Our photoionization analysis of emission and absorption lines in the Chandra grating spectra implies the same wind geometry as XRISM and allows us to measure a characteristic timescale <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">w</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> <mml:mo>/</mml:mo> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̈</mml:mo> </mml:mrow> </mml:mover> <mml:mo>=</mml:mo> <mml:mn>2</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>5.8</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> days. Depending on the scattering geometry, the intrinsic luminosity inferred from our Chandra observations could be substantially super-Eddington, and we suggest that the extended period of super-Eddington luminosity is likely responsible for this massive wind.