An X-ray view of Mrk 705: A borderline narrow-line Seyfert 1 galaxy

TL;DR

This study analyzes over twelve years of X-ray data from multiple observatories to understand the variability and spectral features of Mrk 705, a borderline Seyfert 1 galaxy, revealing mostly typical BLS1 characteristics.

Contribution

It provides a comprehensive multi-epoch X-ray analysis of Mrk 705, highlighting its spectral stability and rare large outbursts, and clarifies the origin of its emission line.

Findings

Modest long-term flux variability (~3 times)

Rare large amplitude outbursts observed in RXTE data

Emission line at 6.4 keV likely from distant material

Abstract

Mrk 705 exhibits optical properties of both narrow- and broad-line Seyfert 1 galaxies. We examine the X-ray properties of this borderline object utilising proprietary and public data from Chandra, ASCA, ROSAT and RXTE, spanning more than twelve years. Though long-term flux variability from the pointed observations appears rather modest (about 3 times), we do find examples of rare large amplitude outbursts in the RXTE monitoring data. There is very little evidence of long-term spectral variability as the low- and high-energy spectra appear constant with time. A 6.4 keV emission line is detected in the ASCA spectra of Mrk 705, but not during the later, higher flux state Chandra observation. However, the upper limit on the equivalent width of a line in the Chandra spectrum is consistent with a constant-flux emission line and a brighter continuum, suggesting that the line is emitted from distant material such as the putative torus. Overall, the X-ray properties of Mrk 705 appear typical of BLS1 activity.