The X-ray variable sky as seen by MAXI: the future of dust echo tomography with bright Galactic X-ray bursts

Abstract

Bright, short duration X-ray flares from accreting compact objects produce thin, dust scattering rings that enable dust echo tomography: high precision distance measurements and mapping of the line-of-sight distribution of dust. This work looks to the past activity of X-ray transient outbursts in order to predict the number of sight lines available for dust echo tomography. We search for and measure the properties of 3$\sigma$ significant flares in the 2-4 keV light curves of all objects available in the public MAXI archive. We derive a fluence sensitivity limit of $10^{-3}$ erg cm${}^{-2}$ for the techniques used to analyze the light curves. This limits the study mainly to flares from Galactic X-ray sources. We obtain the number density of flares and estimate the total fluence of the corresponding dust echoes. However, the sharpness of a dust echo ring depends on the duration of a flare relative to quiescence. We select flares that are shorter than their corresponding quiescent period to calculate a number density distribution for dust echo rings as a function of fluence. The results are fit with a power law of slope $-2.3\pm 0.1$. Extrapolating this to dimmer flares, we estimate that the next generation of X-ray telescopes will be 30 times more sensitive than current observatories, resulting in 10-30 dust ring echoes per year. The new telescopes will also be 10-100 times more sensitive than Chandra to dust ring echoes from the intergalactic medium.

arXiv commentaccepted to ApJ

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Cited by in corpus (4)

• A giant X-ray dust scattering ring around the black hole transient MAXI J1348-630 discovered with SRG/eROSITA
• Ray-tracing simulations and spectral models of X-ray radiation in dusty media
• Interstellar absorption and dust scattering
• Astrophysics with the Laser Interferometer Space Antenna