J/A+A/657/A122 Mrk 926 spectra (Kollatschny+, 2022)
The Great Slump: Mrk926 reveals discrete and varying Balmer line satellite
components during a drastic phase of decline.
Kollatschny W., Ochmann M.W., Kaspi S., Schumacher C., Behar E.,
Chelouche D., Horne K., Mueller B., Rafter S.E., Chini R., Haas M.,
Probst M.A.
<Astron. Astrophys. 657, A122 (2022)>
=2022A&A...657A.122K 2022A&A...657A.122K (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Spectroscopy ; Spectrophotometry
Keywords: galaxies: active - galaxies: Seyfert - galaxies: nuclei -
galaxies: individual: Mrk926 - quasars: emission lines
Abstract:
Mrk926 is known to be a highly-variable AGN. Furthermore, it is known
to show very broad-line profiles. We intended to study the continuum
and line profile variations of this object with high temporal
resolution in order to determine its broad-line region (BLR)
structure, and to derive its black hole (BH) mass.
We carried out a high-cadence spectroscopic variability campaign of
Mrk926 with the 10m HET telescope, aided by photometric V-band data
taken with the C18 telescope at the Wise Observatory, over a period of
about five months. We extracted spectroscopic continuum and line light
curves, and computed cross-correlation functions (CCFs) as well as
velocity-resolved CCFs with respect to the combined spectroscopic and
photometric V-band light curve.
The continuum luminosity of Mrk926 showed a drastic decrease during
our campaign. The luminosity dropped to less than 50% of its original
luminosity within 2.5 months only. Furthermore, the spectra of Mrk926
show complex and very broad Balmer line profiles including outer
Balmer satellites ranging from ±5000 to ±13000km/s. The integrated
Hα, Hβ and HeI5876 line light curves are delayed relative
to the continuum light curve. The Ha and Hb lines show two
velocity-delay structures in the central part of their line profile
(within ±5000km/s) at ∼10 and ∼57 light-days, and at ∼5 and ∼48
light-days, respectively. These structures might be interpreted as the
upper and lower half of an ellipse in the velocity-delay plane, that
might be the signature of a line-emitting ring, inclined by ∼50°
to the line of sight, orbiting the black hole at radii R of 33.5 and
26.5 light-days. We determined continuum luminosities
log(λ*L(λ)/erg/s) of 43.68 to 44.13 which are in good
agreement with the established R(BLR)-L(AGN) relation. Adopting
delays of 33.5 and 26.5 days for Ha and Hb, respectively, we derive a
black hole mass of 1.1±0.2*108M☉ which indicates a low
Eddington ratio decreasing from 8 to 3 percent during our campaign.
The Balmer satellite components show a higher correlation coefficient
with respect to the continuum than the central line profile, and their
response to the continuum variations is of the order of only 3-5 days.
We attribute this to the central line segment and the Balmer
satellites having different, spatially distinct regions of origin.
Description:
We provide 31 reduced spectra of Mrk 926 obtained using the Low
Resolution Spectrograph (LRS) attached at the prime focus of the 10m
Hobby-Eberly telescope (HET). Mrk 926 was observed at 31 epochs
between 2010 July 19 and 2020 November 19. The detector was a
3072x1024 15µpixel Ford Aerospace CCD with 2x2 binning. The spectra
cover the wavelength range from 4160 AA to 6930 AA (LRS grism 2
configuration) in the rest frame of the galaxy (and 4350Å to
7250Å in the observed frame). The resolving power amounts to 650 at
5000Å (7.7Å FWHM). The data is flux-calibrated (see FITS keyword
BUNIT) and intercalibrated to a [OIII]5007 flux of
3.14*1013erg/cm2/s. All relevant information is contained in the
FITS headers, including the world coordinates.
Additionally, we provide a photometric light curve, in arbitrary flux
units, observed with a Bessell V-band filter at the C18 telescope of
the Wise Observatory, from 2010 August 28 to 2010 December 10. The
SBIG STL-6303 CCD was used with 3072x2048 9mu pixel, and a plate-scale
of 1.47arcsec/pix. This gives a field of view of 75x50arcmin. Each
night several exposures of 5min each were obtained. Measurements from
the same night were averaged to obtain a single measurement for each
night in order to decrease the uncertainty on each point in the light
curve. The light curve was intercalibrated to the 5420Å light curve
of the HET.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
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23 04 43.48 -08 41 08.6 Mrk926 = LEDA 70409
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
wisevmod.dat 33 64 Photometric light curve
list.dat 107 31 List of fits spectra
fits/* . 31 Individual spectra
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Byte-by-byte Description of file: wisevmod.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 F15.7 d JD Julian date
17- 24 F8.6 --- Flux Flux in Bessell V band (arbitrary unit)
26- 33 F8.6 --- e_Flux Flux error (arbitrary unit)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Nx Number of pixels along X-axis
6- 15 A10 "date" Obs.date Observation date
17- 20 I4 0.1nm blambda Lower value of wavelength interval
22- 28 F7.2 0.1nm Blambda Upper value of wavelength interval
30- 35 F6.4 0.1nm dlambda Wavelegnth resolution
37- 38 I2 Kibyte size Size of FITS file
40- 69 A30 --- FileName Name of FITS file, in subdirectory fits
71-107 A37 --- Title Title of the FITS file
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Acknowledgements:
Wolfram Kollatschny, wkollat(at)astro.physik.uni-goettingen.de
(End) Patricia Vannier [CDS] 15-Oct-2021