XMM-Newton first X-ray detection of the LoBAL quasar PG 1700+518

TL;DR

This paper reports the first high-energy X-ray detection of the LoBAL quasar PG 1700+518 using XMM-Newton, revealing strong absorption features and confirming its X-ray weakness, which challenges previous non-detection assumptions.

Contribution

First high-energy X-ray detection of PG 1700+518, providing insights into its absorption properties and X-ray weakness, using XMM-Newton observations.

Findings

Spectrum below 2 keV is very steep (Gamma ~ 2.4-3.8).

At higher energies, the emission is extremely flat, indicating strong absorption or reflection.

The X-ray flux is consistent with previous non-detections, confirming its X-ray weakness.

Abstract

We report the first high-energy detection of PG 1700+518, a well-known low-ionization broad absorption line quasar (QSO). Due to previous X-ray non-detection, it was classified as soft X-ray weak QSO. We observed PG 1700+518 with XMM-Newton for about 60 ksec divided in three exposures. The spectrum below 2 keV is very steep, Gamma ~ 2.4-3.8, while at higher energies the extremely flat emission (photon index Gamma ~ 0.15, when modelled with a power law) suggests the presence of strong absorption (NH,pl ~ 2\times10^23 cm-2, Gamma fixed to 1.8), or a reflection-dominated continuum. The broad-band flux is consistent with previous non-detection. Simultaneous EPIC and OM data confirm its X-ray weakness (alpha_ox = -2.2). The level of obscuration derived from the X-ray spectra of PG 1700+518 cannot explain its soft X-ray nuclear weakness unless a column density of NH >~ 2\times10^24 cm-2 is present.