X-ray obscuration from a variable ionized absorber in PG 1114+445

¹ INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20121, Milano; Via Bianchi 46, 23807 Merate (LC), Italy
e-mail: roberto.serafinelli@inaf.it
² Department of Physics, Institute for Astrophysics and Computational Sciences, The Catholic University of America, Washington, DC 20064, USA
³ Dipartimento di Fisica, Università degli Studi di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
⁴ X-ray Astrophysics Laboratory, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁵ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
⁶ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Monte Porzio Catone, Roma, Italy
⁷ Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria, 16, 20133 Milano, Italy
⁸ INAF – Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
⁹ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, via P. Gobetti 93/3, 40129 Bologna, Italy
¹⁰ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
¹¹ Space Science Data Center, Agenzia Spaziale Italiana, Via del Politecnico snc, 00133 Roma, Italy
¹² Núcleo de Astronomía de la Facultad de Ingeniería, Universitad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile

Received: 4 June 2021
Accepted: 13 July 2021

Abstract

Photoionized absorbers of outflowing gas are commonly found in the X-ray spectra of active galactic nuclei. While most of these absorbers are seldom significantly variable, some ionized obscurers have increasingly been found to substantially change their column density on a wide range of timescales. These N_H variations are often considered as the signature of the clumpy nature of the absorbers. Here we present the analysis of a new Neil Gehrels Swift Observatory campaign of the type 1 quasar PG 1114+445, which was observed to investigate the time evolution of the multiphase outflowing absorbers previously detected in its spectra. The analyzed dataset consists of 22 observations with a total exposure of ∼90 ks that spans about 20 months. For the whole campaign, we report an unusually low flux state with respect to all previous X-ray observations of this quasar. From the analysis of the stacked spectra, we find a fully covering absorber with a column density log(N_H/cm⁻²) = 22.9_−0.1^+0.3. This is an order of magnitude higher than the column density measured in the previous observations. This is either due to a variation of the known absorbers or to a new one that eclipses the X-ray emitting source. We also find an ionization parameter of log(ξ/erg cm s⁻¹) = 1.4_−0.2^+0.6. Assuming that the obscuration lasts for the whole duration of the campaign, that is, more than 20 months, we estimate the minimum distance of the ionized clump, which is located at r ≳ 0.5 pc.