XTE J1901+014 - the First Low-Mass Fast X-ray Transient?

TL;DR

This study analyzes XTE J1901+014 using multi-wavelength observations, suggesting it may be the first low-mass fast X-ray transient due to its stable quiescent emission and optical companion characteristics.

Contribution

The paper provides the first detailed multi-wavelength analysis of XTE J1901+014, proposing its classification as a low-mass fast X-ray transient based on new optical and X-ray data.

Findings

XTE J1901+014 shows stable emission in quiescence.

Optical counterpart could be a low-mass star or distant giant.

The source may be the first low-mass fast X-ray transient.

Abstract

We continue to study the fast X-ray transient XTE J1901+014 discovered in 2002 by the RXTE observatory, whose nature has not yet been established. Based on the XMM-Newton observations of the source in 2006, we have obtained its energy spectrum, light curves, and power spectrum in the energy range 0.5-12 keV, which are in good agreement with our results obtained previously from the data of other observatories. In turn, this suggests that the source's emission is stable in the quiescent state. The XMM-Newton observations also allowed the source's localization accuracy to be improved to <2", which subsequently enabled us to search for its optical companion with the RTT-150 and 6-m BTA (Special Astrophysical Observatory) telescopes. Combining optical, X-ray, and infrared observations, we have concluded that the optical companion in the system under study can be either a later-type star at a distance of several kpc or a very distant red giant or an A or F star. Thus, XTE J1901+014 may be the first low-mass fast X-ray transient.