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Title: FIRST LONG-TERM OPTICAL SPECTRAL MONITORING OF A BINARY BLACK HOLE CANDIDATE E1821+643. I. VARIABILITY OF SPECTRAL LINES AND CONTINUUM

We report the results of the first long-term (1990–2014) optical spectrophotometric monitoring of a binary black hole candidate QSO E1821+643, a low-redshift, high-luminosity, radio-quiet quasar. In the monitored period, the continua and Hγ fluxes changed about two times, while the Hβ flux changed about 1.4 times. We found periodical variations in the photometric flux with periods of 1200, 1850, and 4000 days, and 4500-day periodicity in the spectroscopic variations. However, the periodicity of 4000–4500 days covers only one cycle of variation and should be confirmed with a longer monitoring campaign. There is an indication of the period around 1300 days in the spectroscopic light curves, buts with small significance level, while the 1850-day period could not be clearly identified in the spectroscopic light curves. The line profiles have not significantly changed, showing an important red asymmetry and broad line peak redshifted around +1000 km s{sup −1}. However, Hβ shows a broader mean profile and has a larger time lag (τ ∼ 120 days) than Hγ (τ ∼ 60 days). We estimate that the mass of the black hole is ∼2.6 × 10{sup 9} M{sub ⊙}. The obtained results are discussed in the frame of the binary black hole hypothesis. To explain the periodicity in the fluxmore » variability and high redshift of the broad lines, we discuss a scenario where dense, gas-rich, cloudy-like structures are orbiting around a recoiling black hole.« less
Authors:
; ;  [1] ;  [2] ; ; ; ; ;  [3] ; ;  [4] ;  [5]
  1. Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz, Karachaevo-Cherkesia 369167 (Russian Federation)
  2. Astronomical Observatory, Volgina 7, 11160 Belgrade 74 (Serbia)
  3. Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, Puebla, México (Mexico)
  4. Department of Astronomy, Faculty of Mathematics, University of Belgrade, Studentski trg 16, 11000 Belgrade (Serbia)
  5. Institut für Astrophysik, Georg-August-Universität Göttingen (Germany)
Publication Date:
OSTI Identifier:
22519981
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 222; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; DIAGRAMS; GALAXIES; LUMINOSITY; MASS; MONITORING; PERIODICITY; PHOTOMETRY; QUASARS; RED SHIFT; SPECTROPHOTOMETRY; VISIBLE RADIATION