2016/01/14 by A. I. Shapovalova, L. Č. Popović, L. C. Popovic +15 · 28 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Asymmetry #Binary black hole #Binary number #Black hole (networking) #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Line (geometry) #Redshift #Spectral line #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.3847/0067-0049/222/2/25
published in The Astrophysical Journal Supplement Series 222(2), 25 (Institute of Physics) · Accepted in ApJS
arxiv created 2016/01/14 · openalex publication_date 2016/02/01 · arxiv updated 2016/03/23 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
ABSTRACT 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 H γ fluxes changed about two times, while the H β 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 −1 . However, H β shows a broader mean profile and has a larger time lag ( τ ∼ 120 days) than H γ ( τ ∼ 60 days). We estimate that the mass of the black hole is ∼2.6 × 10 9 M ⊙ . The obtained results are discussed in the frame of the binary black hole hypothesis. To explain the periodicity in the flux 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.