Long Term Radiative Behavior of SGR 1900+14

TL;DR

This study analyzes seven years of X-ray data from magnetar SGR 1900+14, revealing consistent flux decline patterns after outbursts and stable magnetic properties, with surface temperature and emitting area decreasing over time.

Contribution

It provides a detailed long-term spectral and flux evolution analysis of SGR 1900+14, highlighting the stability of magnetic features and the consistent flux level in quiescence.

Findings

Flux decline follows a similar pattern after outbursts.

Magnetic field strength remains unchanged over the observation period.

Surface temperature and emitting area decrease with time.

Abstract

The prolific magnetar SGR 1900+14 showed two outbursts in the last decade and has been closely monitored in the X-rays to track the changes in its radiative properties. We use archival Chandra and XMM-Newton observations of SGR 1900+14 to construct a history of its spectrum and persistent X-ray flux spanning a period of about seven years. We show that the decline of its X-ray flux in these two outburst episodes follows the same trend. The flux begins to decline promptly and rapidly subsequent to the flares, then decreases gradually for about 600 days, at which point it resumes a more rapid decline. Utilizing the high quality spectral data in each epoch, we also study the spectral coevolution of the source with its flux. We find that neither the magnetic field strength nor the magnetospheric properties change over the period spanned by the observations, while the surface temperature as well as the inferred emitting area both decline with time following both outbursts. We also show that the source reached the same minimum flux level in its decline from these two subsequent outbursts, suggesting that this flux level may be its steady quiescent flux.