Spectral optical monitoring of the double-peaked emission line AGN Arp 102B

II. Variability of the broad line properties^⋆

¹ Astronomical Observatory, Volgina 7, 11160 Belgrade 74, Serbia
e-mail: ashap@sao.ru
² Isaac Newton Institute of Chile, Yugoslavia Branch, 11060 Belgrade, Serbia
³ Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz, 369167 Karachaevo-Cherkesia, Russia
⁴ Department of Astronomy, Faculty of Mathematics, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia
⁵ Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51, CP 72000, Puebla, Pue. México, Mexico
⁶ Institut für Astrophysik, Friedrich-Hund-Platz 1, Göttingen, Germany
⁷ Sternberg Astronomical Institute, Moscow, Russia
⁸ Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland

Received: 1 February 2014
Accepted: 23 August 2014

Abstract

Context. We investigate the long-term (26 years, from 1987 to 2013) variability in the broad spectral line properties of the radio galaxy Arp 102B, an active galaxy with broad double-peaked emission lines. We use observations presented in Paper I in the period from 1987 to 2011, and a new set of observations performed in 2012–2013.

Aims. We explore variations in the Hα and Hβ line parameters during the monitored period to explore the broad-line region (BLR) geometry and to clarify some contradictions about the nature of the BLR in Arp102B.

Methods. We fit the broad lines with three broad Gaussian functions finding the positions and intensities of the blue and red peaks in Hα and Hβ. Additionally, we fit averaged line profiles with the disk model.

Results. We find that the broad line profiles are double peaked and have not been changed significantly in shapes, beside an additional small peak that from time to time can be seen in the blue part of the Hα line. The positions of the blue and red peaks have not changed significantly during the monitored period. The Hβ line is broader than Hα line in the monitored period. The disk model is able to reproduce the Hβ and Hα broad line profiles, however, observed variability in the line parameters are not in good agreement with the emission disk hypothesis.

Conclusions. It seems that the BLR of Arp 102B has a disk-like geometry, but the role of an outflow can also play an important role in observed variation of the broad line properties.