Bibcode
Serra-Ricart, M.; Oscoz, A.
Referencia bibliográfica
American Astronomical Society, 190th AAS Meeting, #33.08; Bulletin of the American Astronomical Society, Vol. 29, p.822
Advertised on:
5
1997
Número de citas
0
Número de citas referidas
0
Descripción
Gravitational lenses are a consequence of the bending of light rays,
which is one of the "classical" tests of Einsteins' General Relativity.
This phenomenon appears when a large amount of mass, one or several
galaxies, is located near the line-of-sight connecting the observer with
a remote bright source, a quasar, far-off from both objects. In this
case, the light traveling between the source and the observer can, due
to the gravitational bending, follow two different paths, each of them
at a different side of the central mass, which offers the possibility to
observe two identical images of the source. If the emission from the
quasar presents variability, the fluctuations in each image should be
correlated: as the time light spends in traveling along different path
varies from image to image, the light curves observed will follow the
same pattern, but with an offset in time.After the discovery of the
first gravitational lens, the double quasar 0957+561, in 1979, a great
deal of effort to obtain the time delay between its two components has
been made. This system consists of a pair of identical images, A and B
(R magnitude 16, separation 6.1 arcsec), resulting from the bending by a
cluster of galaxies of the light emitted from a quasar. Although a
continuous monitoring of both components in several bands has been
performed since the detection of 0957+561 there are, however, several
controversies regarding the value of such time delay. It was only known
that image B arrives with a delay larger than a year with respect to
component A. The knowledge of the time delay between the images of a
gravitationally lensed object is essential to determine the value of the
Hubble constant, a quantity related with the age of the Universe and
with cosmic distances, and to develop theoretical studies of the lensing
object. Those are the reasons why an optical monitoring of the double
quasar 0957+561 was set (see http://www.iac.es/lent) at the beginning of
1996 using the CCD camera of the 82 cm IAC80 telescope sited at the
Instituto de Astrofisica de Canarias's Teide Observatory (Tenerife,
Spain). However it still remains a great uncertainty in the value of the
Hubble constant, and so it would be very useful to obtain the light
curves as complete as possible. To do it, the contribution of the
amateur astronomers is essential in order to obtain so many observations
as possible (see http://www.iac.es/lent/amateur/light.hml for more
details). With them, besides of obtaining the value of the Hubble
constant, we could detect microlensing events, which give an estimation
of the dark matter present both in the lensing galaxy and in our galaxy.
In the same way, the detection of those phenomena would give information
on the emitter, which is supposed to be an enormous black hole with and
accretion disk around it.