NuSTAR reveals the extreme properties of the super-Eddington accreting supermassive black hole in PG 1247+267

¹ Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
e-mail: giorgio.lanzuisi2@unibo.it
² INAF−Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ INAF−Istituto di Astrofisica Spaziale e Fisica Cosmica, via Piero Gobetti 101, 40129 Bologna, Italy
⁴ Dipartimento di Matematica e Fisica, Università di Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
⁵ Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
⁶ Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, 837 State St., Atlanta, GA 30332, USA
⁷ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
⁸ Millennium Institute of Astrophysics, Vicuna Mackenna 4860, 7820436 Macul, Santiago, Chile
⁹ Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
¹⁰ Space Science Laboratory, University of California, Berkeley, CA 94720, USA
¹¹ Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802, USA
¹² Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
¹³ Department of Physics, 104 Davey Lab, The Pennsylvania State University, University Park, PA 16802, USA
¹⁴ DTU Space National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Lyngby, Denmark
¹⁵ Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
¹⁶ Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
¹⁷ Department of Physics, Virginia Tech, Blacksburg, VA 24061, USA
¹⁸ Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA
¹⁹ Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
²⁰ School of Astronomy and Space Science, Nanjing University, Nanjing, 210093, PR China
²¹ Key laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, 210093 Nanjing, PR China
²² INAF−Osservatorio Astronomico di Roma, via di Frascati, 33, 00040 Monteporzio Catone (Roma), Italy
²³ ASDC–ASI, via del Politecnico, 00133 Roma, Italy
²⁴ Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, 305348 Daejeon, Korea
²⁵ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
²⁶ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received: 17 February 2016
Accepted: 21 March 2016

Abstract

PG1247+267 is one of the most luminous known quasars at z ~ 2 and is a strongly super-Eddington accreting supermassive black hole (SMBH) candidate. We obtained NuSTAR data of this intriguing source in December 2014 with the aim of studying its high-energy emission, leveraging the broad band covered by the new NuSTAR and the archival XMM-Newton data. Several measurements are in agreement with the super-Eddington scenario for PG1247+267: the soft power law (Γ = 2.3 ± 0.1); the weak ionized Fe emission line; and a hint of the presence of outflowing ionized gas surrounding the SMBH. The presence of an extreme reflection component is instead at odds with the high accretion rate proposed for this quasar. This can be explained with three different scenarios; all of them are in good agreement with the existing data, but imply very different conclusions: i) a variable primary power law observed in a low state, superimposed on a reflection component echoing a past, higher flux state; ii) a power law continuum obscured by an ionized, Compton thick, partial covering absorber; and iii) a relativistic disk reflector in a lamp-post geometry, with low coronal height and high BH spin. The first model is able to explain the high reflection component in terms of variability. The second does not require any reflection to reproduce the hard emission, while a rather low high-energy cutoff of ~100 keV is detected for the first time in such a high redshift source. The third model require a face-on geometry, which may affect the SMBH mass and Eddington ratio measurements. Deeper X-ray broad-band data are required in order to distinguish between these possibilities.