Issue |
A&A
Volume 447, Number 3, March I 2006
|
|
---|---|---|
Page(s) | 905 - 913 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20053574 | |
Published online | 10 February 2006 |
Observational determination of the time delays in gravitational lens system Q2237+0305
1
Institute of Astronomy of Kharkov National University, Sumskaya 35, 61022 Kharkov, Ukraine e-mail: vakulik@astron.kharkov.ua
2
Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
3
Ulugh Beg Astronomical Institute of Ac.Sci. of Uzbekistan, Astronomicheskaya 33, 700052 Tashkent, Republic of Uzbekistan
4
Institute of Radio Astronomy of Nat. Ac. Sci. of Ukraine, Krasnoznamennaya 4, 61002 Kharkov, Ukraine
Received:
4
June
2005
Accepted:
26
October
2005
We present new brightness monitoring observations of the
4 components of gravitationally lensed system Q2237+0305,
which show detection of an intrinsic quasar brightness fluctuation
at a time of subdued microlensing activity, between June 27 and
October 12, 2003. These data were used to determine the time delays
between the arrivals of the four images. The measured delays are
,
, and
h, so they confirm that the long history of brightness monitoring
has produced significant detection of microlensing. However the error
bars associated with the delays, of order 2 days, are too large to
discriminate between competing macro-imaging models. Moreover, our
simulations show that for the amplitude of this intrinsic fluctuation
and for photometric errors intrinsic to optical monitoring from our
1.5-m telescope or from the OGLE monitoring, a daily sampled
brightness record cannot produce reliable lags for model discrimination.
We use our simulations to devise a strategy for future delay
determination with optical data. Nevertheless, we regard these first
estimates to be significant, since they are the first direct
measurements of time delays made for this system from ground-based
observations in the visual wavelengths. The detected highly
correlated fluctuations of the four quasar images provide an extra
confirmation of the gravitational-lens nature of Q2237+0305,
and give observational justification to the extensive literature which
attributes the quasar's previously observed brightness fluctuations to
microlensing.
Key words: gravitational lensing / quasars: individual: Q2237+0305 / methods: observational
© ESO, 2006
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