2018/04/16 by M. Zetzl, W. Kollatschny, M. W. Ochmann +8 · 1 citation
Chemistry · Physics and Astronomy · #Accretion (finance) #Amplitude #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Chemistry #Flux (metallurgy) #Galaxy #Gamma-ray bursts and supernovae #Lambda #Optics #Physics #Spectral line #Wavelength #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/201732506
published as A&A 618, A83 (2018) · 25 pages, 21 figures, Astronomy & Astrophysics in press
arxiv created 2018/04/16 · openalex publication_date 2018/04/20 · arxiv updated 2018/10/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Aims. A strong outburst in the X-ray continuum and a change of its Seyfert spectral type was detected in HE 1136-2304 in 2014. The spectral type changed from nearly Seyfert 2 type (1.95) to Seyfert 1.5 type in comparison to previous observations taken ten to twenty years before. In a subsequent variability campaign we wanted to investigate whether this outburst was a single event or whether the variability pattern following the outburst was similar to those seen in other variable Seyfert galaxies. Methods. In addition to a SALT spectral variability campaign, we carried out optical continuum, as well as X-ray and UV ( Swift ) monitoring studies from 2014 to 2017. Results. HE 1136-2304 strongly varied on timescales of days to months from 2014 to 2017. No systematic trends were found in the variability behavior following the outburst in 2014. A general decrease in flux would have been expected for a tidal disruption event. This could not be confirmed. More likely the flux variations are connected to irregular fluctuations in the accretion rate. The strongest variability amplitudes have been found in the X-ray regime: HE 1136-2304 varied by a factor of eight during 2015. The amplitudes of the continuum variability (from the UV to the optical) systematically decreased with wavelength following a power law F var = a × λ − c with c = 0.84. There is a trend that the B -band continuum shows a delay of three light days with respect to the variable X-ray flux. The Seyfert type 1.5 did not change despite the strong continuum variations for the period between 2014 and 2017.