J/A+A/637/A89 QSO 2237+0305 photometry and light curves (Goicoechea+, 2020)
Liverpool-Maidanak monitoring of the Einstein Cross in 2006-2019.
I. Light curves in the gVrRI optical bands and microlensing signatures.
Goicoechea L.J., Artamonov B.P., Shalyapin V.N., Sergeyev A.V.,
Burkhonov O.A., Akhunov T.A., Asfandiyarov I.M., Bruevich V.V.,
Ehgamberdiev S.A., Shimanovskaya E.V., Zheleznyak A.P.
<Astron. Astrophys. 637, A89 (2020)>
=2020A&A...637A..89G 2020A&A...637A..89G (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Gravitational lensing ; Photometry, CCD
Keywords: techniques: photometric - methods: data analysis -
gravitational lensing: strong - gravitational lensing: micro -
quasars: individual: QSO 2237+0305
Abstract:
Quasar microlensing offers a unique opportunity to resolve tiny
sources in distant active galactic nuclei and study compact object
populations in lensing galaxies. We therefore searched for
microlensing-induced variability of the gravitationally lensed quasar
QSO 2237+0305 (Einstein Cross) using 4374 optical frames taken with
the 2.0m Liverpool Telescope and the 1.5m Maidanak Telescope. These
gVrRI frames over the 2006-2019 period were homogeneously processed
to generate accurate long-term multi-band light curves of the four
quasar images A-D. Through difference light curves, we found strong
microlensing signatures. We then focused on the analytical modelling
of two putative caustic-crossing events in image C, finding compelling
evidence that this image experienced a double caustic crossing.
Additionally, our overall results indicate that a standard accretion
disc accounts reasonably well for the brightness profile of UV
continuum emission sources and for the growth in source radius when
the emission wavelength increases:
Rλ∝λα, α=1.33±0.09. However,
we caution that numerical microlensing simulations are required before
firm conclusions can be reached on the UV emission scenario because
the VRI-band monitoring during the first caustic crossing and one of
our two α indicators lead to a few good solutions with
α≈1.
Description:
We conducted an optical monitoring campaign of the gravitationally
lensed quasar QSO 2237+0305 (Einstein Cross) using the 2.0m Liverpool
Telescope and the 1.5m Maidanak Telescope. This campaign rendered
4374 optical frames in the gVrRI bands over the 2006-2019 period. All
frames were homogeneously processed to construct accurate long-term,
multi-band light curves of the four quasar images A, B, C, and D.
Tables 4-8 show detailed photometric results for all individual
frames, while Tables 10, 11, 12, 13, and 14 include light curves in
the g, V, r, R, and I bands, respectively. Extended (updated) light
curves will be available at the GLENDAMA website
(http://grupos.unican.es/glendama/q2237.htm).
Objects:
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RA (2000) DE Designation(s)
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22 40 30.23 +03 21 30.6 QSO 2237+0305 = NAME Einstein Cross
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 81 277 Photometry in the g band
table5.dat 81 731 Photometry in the V band
table6.dat 81 366 Photometry in the r band
table7.dat 81 2295 Photometry in the R band
table8.dat 81 705 Photometry in the I band
table10.dat 73 203 Light curves in the g band (479.5nm)
table11.dat 73 180 Light curves in the V band (539.6nm)
table12.dat 73 253 *Light curves in the r band (618.7nm)
table13.dat 73 445 Light curves in the R band (646.2nm)
table14.dat 73 179 Light curves in the I band (839.1nm)
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Note on table12.dat: table12 is an extended version of J/A+A/616/A118/table16 in
Gil-Merino et al. (2018A&A...616A.118G 2018A&A...616A.118G).
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See also:
J/A+A/616/A118 : Lensed QSOs light curves & spectral monitoring
(Gil-Merino+, 2018)
https://grupos.unican.es/glendama/LQLM_results.htm : Project Home Page
Byte-by-byte Description of file: table[45678].dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Date Civil date_frame number (yymmdd_no)
11- 18 F8.3 d MJD Modified Julian Date (MJD-50000)
20- 22 I3 s Texp Exposure time
24- 27 F4.2 arcsec PSFfwhm Full width at half-maximum of the
Point Spread Function (PSF)
29- 32 F4.2 --- PSFellip Ellipticity of the PSF
34- 36 I3 --- S/N Signal-to-noise ratio (alpha star)
38- 43 F6.3 mag mA Magnitude of QSO 2237+0305A
45- 50 F6.3 mag mB ? Magnitude of QSO 2237+0305B
52- 57 F6.3 mag mC ? Magnitude of QSO 2237+0305C
59- 64 F6.3 mag mD ? Magnitude of QSO 2237+0305D
66- 71 F6.3 mag mbeta Magnitude of the beta star
73- 79 F7.3 --- chi2/dof Reduced chi-square value on the QSO
subframe using IMFITFITS software (1)
81 A1 --- Quality [*] Poor-quality frames are marked with
an asterisk
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Note (1): We used the IMFITFITS software for fitting a two-dimensional
multi-component photometric model to subframes containing the
gravitational lens system (e.g. 1998AJ....115.1377M 1998AJ....115.1377M)
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Byte-by-byte Description of file: table1[01234].dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 d MJD Modified Julian Date (MJD-50000)
10- 15 F6.3 mag mA Magnitude of QSO 2237+0305A
17- 21 F5.3 mag e_mA Error in magnitude of QSO 2237+0305A
23- 28 F6.3 mag mB Magnitude of QSO 2237+0305B
30- 34 F5.3 mag e_mB Error in magnitude of QSO 2237+0305B
36- 41 F6.3 mag mC Magnitude of QSO 2237+0305C
43- 47 F5.3 mag e_mC Error in magnitude of QSO 2237+0305C
49- 54 F6.3 mag mD Magnitude of QSO 2237+0305D
56- 60 F5.3 mag e_mD Error in magnitude of QSO 2237+0305D
62- 67 F6.3 mag mbeta Magnitude of the beta star
69- 73 F5.3 mag e_mbeta Error in magnitude of the beta star
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Acknowledgements:
Luis J. Goicoechea, goicol(at)unican.es
(End) L. Goicoechea [Univ. de Cantabria, Spain], P. Vannier [CDS] 11-Apr-2020