J/A+A/668/A77 R-band light curves of QSO J0158-4325 images (Millon+, 2022)
Evidence for a milliparsec-separation supermassive binary black hole with
quasar microlensing.
Millon M., Dalang C., Lemon C., Sluse D., Paic E., Chan J.H.H., Courbin F.
<Astron. Astrophys. 668, A77 (2022)>
=2022A&A...668A..77M 2022A&A...668A..77M (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Gravitational lensing ; Photometry ; Optical
Keywords: gravitational lensing: micro - quasars: supermassive black holes -
methods: data analysis
Abstract:
We report periodic oscillations in the 15-year-long optical light
curve of the gravitationally lensed quasar J0158-4325 at zs=1.29.
The signal is enhanced during a high magnification microlensing event
of the quasar that the fainter lensed image, B, underwent between 2003
and 2010. We measure a period of Po=172.6±0.9 days, which
translates to 75.4±0.4 days in the quasar frame. The
oscillations have a maximum amplitude of 0.26±0.02mag and decrease
concurrently with the smooth microlensing amplitude. We explore four
scenarios to explain the origin of the periodicity: (1) the high
magnification microlensing event is due to a binary star in the
lensing galaxy, (2) J0158-4325 contains a supermassive binary black
hole system in its final dynamical stage before merging, (3) the
quasar accretion disk contains a bright inhomogeneity in Keplerian
motion around the black hole, and (4) the accretion disk is in
precession.
Of these four scenarios, only a supermassive binary black hole can
account for both the short observed period and the amplitude of the
signal, through the oscillation of the accretion disk towards and away
from high-magnification regions of a microlensing caustic. The short
measured period implies that the semi-major axis of the orbit is
∼10-3pc and that and the coalescence timescale is tcoal∼1000
years, assuming that the decay of the orbit is solely powered by the
emission of gravitational waves. The probability of observing a system
so close to coalescence, in a sample of only 30 monitored lensed
quasars, suggests either a much larger population of supermassive
binary black holes than predicted or, more likely, that some other
mechanism significantly increases the coalescence timescale. Three
tests of the binary black hole hypothesis include: (i) the recurrence
of oscillations in photometric monitoring during any future
microlensing events in either image, (ii) spectroscopic detection of
Doppler shifts (up to ∼0.01c) associated with optical emission in the
vicinity of the black holes, and (iii) the detection of gravitational
waves through pulsar timing array experiments, such as the Square
Kilometre Array, which will have the sensitivity to detect the ∼100
nano-hertz emission.
Description:
R-band cosmograil light curves of lensed quasars taken at the Euler
1.2m Swiss telescope with the EulerCAM and EulerC2 instrument.
Additional data taken at the SMARTS 1.3m telescope with the ANDICAM
optical camera.
Objects:
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RA (2000) DE Designation(s)
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01 58 41.37 -43 25 04.8 QJ0158-4325 = QSO J0158-4325
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
euler.dat 54 527 Euler R-band light curves of QSO J0158-4325
smart.dat 59 252 SMARTS R-band light curves of QSO J0158-4325
eulerb-a.dat 33 485 Euler difference (B-A) light curve
smartb-a.dat 34 229 SMARTS difference (B-A) light curve
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See also:
J/ApJ/756/52 : R-band light curves of QSO J0158-4325 images (Morgan+, 2012)
J/A+A/640/A105 : R-band light curves of 23 lensed QSOs (Millon+, 2020)
Byte-by-byte Description of file: euler.dat smart.dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d HJD Median Heliocentric Julian Date (HJD-2400000)
13- 20 F8.5 mag RmagA R-band magnitude of image A
22- 28 F7.5 mag e_RmagA R-band magnitude error of image A
30- 37 F8.5 mag RmagB R-band magnitude of image B
39- 45 F7.5 mag e_RmagB R-band magnitude error of image B
47- 59 A13 --- Tel Telescope used for the observation
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Byte-by-byte Description of file: eulerb-a.dat smartb-a.dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d HJD Median Heliocentric Julian Date (HJD-2400000)
13- 19 F7.5 mag RmagB-A R-band difference R magnitude B-A
21- 27 F7.5 mag e_RmagB-A R-band difference R magnitude B-A error
29- 34 A6 --- Tel Telescope used for the observation
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Acknowledgements:
Martin Millon, martin.millon(at)epfl.ch
(End) Martin Millon [EPFL, Switzerland], Patricia Vannier [CDS] 17-Oct-2022