X-ray nova MAXI J1828-249. Evolution of the broadband spectrum during its 2013-2014 outburst

TL;DR

This study analyzes the broadband spectrum evolution of the X-ray nova MAXI J1828-249 during its 2013-2014 outburst, revealing that optical and infrared emissions are primarily linked to the same energetic region producing hard X-rays.

Contribution

It provides new insights into the origin of optical and infrared emissions in X-ray novae, emphasizing their connection to the same energy release region as hard X-ray emission.

Findings

Optical/infrared emissions are mainly from the same region as hard X-ray emission.

Outer cold accretion disk contribution is moderate or absent during different states.

Optical/infrared emissions likely originate from high-temperature plasma, corona, or jets.

Abstract

Based on data from the SWIFT, INTEGRAL, MAXI/ISS orbital observatories, and the ground-based RTT-150 telescope, we have investigated the broadband (from the optical to the hard X-ray bands) spectrum of the X-ray nova MAXI J1828-249 and its evolution during the outburst of the source in 2013-2014. The optical and infrared emissions from the nova are shown to be largely determined by the extension of the power-law component responsible for the hard X-ray emission. The contribution from the outer cold regions of the accretion disk, even if the X-ray heating of its surface is taken into account, turns out to be moderate during the source's "high" state (when a soft blackbody emission component is observed in the X-ray spectrum) and is virtually absent during its "low" ("hard") state. This result suggests that much of the optical and infrared emissions from such systems originates in the same region of main energy release where their hard X-ray emission is formed. This can be the Compton or synchro-Compton radiation from a high-temperature plasma in the central accretion disk region puffed up by instabilities, the synchrotron radiation from a hot corona above the disk, or the synchrotron radiation from its relativistic jets.