Optical imaging of gravitational lenses B1422+231

in Surdej, Jean; Fraipont-Caro, D.; Gosset, Eric (Eds.) et al Liege International Astrophysical Colloquia,Gravitational Lenses in the Universe (1993)

We report here on some of the major developments achieved on optical observations of gravitational lenses since the last conference devoted to 'Gravitational Lensing'.

The cloverleaf quasar H1413+117: a preliminary light curve

in Surdej, Jean; Fraipont-Caro, Denise; Gosset, Eric (Eds.) et al The proceedings of the 31st Liège International Astrophysical Colloquium "Gravitational lenses in the Universe" (1993)

The cloverleaf quasar H1413+117 was discovered to be a gravitational lens system in 1988. Since then, it has been photometrically monitored essentially as part of the ESO key-program Gravitational lensing ... [more ▼]

The cloverleaf quasar H1413+117 was discovered to be a gravitational lens system in 1988. Since then, it has been photometrically monitored essentially as part of the ESO key-program Gravitational lensing: we present here a first preliminary lightcurve for its four individual images. [less ▲]

ESO key programme, gravitational lensing: quasars and radio galaxies; a status report

in Distribution of Matter in the Universe (1992, December 01)

The scientific background and objectives of our ESO Key Programme are first recalled. A brief account of our research activities (observing runs at ESO and elsewhere, meetings, etc.) is then given ... [more ▼]

The scientific background and objectives of our ESO Key Programme are first recalled. A brief account of our research activities (observing runs at ESO and elsewhere, meetings, etc.) is then given. Preliminary scientific results are presented concerning 1) our observational database for highly luminous quasars and distant powerful radiogalaxies; 2) speckle observations of highly luminous quasars; 3) the photometric monitoring and 4) detailed studies of several known gravitational lenses; 5) optical observations of 3C and 4C radio galaxies and 6) of the well known Einstein ring MG 1131+0456. [less ▲]

New observations and gravitational lens models of the Cloverleaf quasar H1413 + 117

in Astrophysical Journal (1990), 364

New optical and radio observations of the quadruple quasar H1413 + 117, the Cloverleaf, are presented. VLA data show radio counterparts at the positions of the four optical images and an additional strong ... [more ▼]

New optical and radio observations of the quadruple quasar H1413 + 117, the Cloverleaf, are presented. VLA data show radio counterparts at the positions of the four optical images and an additional strong radio source between images B and D. Gravitational lens models of H1413 + 117 using (1) a single elliptical galaxy and (2) two spherical galaxies are presented, which fit the positions of the four images of the quasar remarkably well. The models suggest that the strong radio source is a feature of the quasar, e.g., an ejected blob, which lies right on the caustic of the lens and is thereby strongly amplified. The time delays predicted by these models are sufficiently short to allow for their determination within one observational season, making H1413 + 117 an exceptionally well suited object for gravitational lens research. [less ▲]

First spectroscopic evidence of microlensing on a BAL quasar? The case of H 1413 + 117

in Astronomy and Astrophysics (1990), 233

New data has been obtained for the quadruply lensed quasar H 1413 + 117 using the bidimensional spectrograph SILFID at the CFH telescope. The spectra recorded for each of the four individual images turn ... [more ▼]

New data has been obtained for the quadruply lensed quasar H 1413 + 117 using the bidimensional spectrograph SILFID at the CFH telescope. The spectra recorded for each of the four individual images turn out to be quite similar, except for the narrow absorption line systems (probably related to the lenses) seen in images A and B and for marked differences in the spectrum of image D. When compared to the three other images, the spectrum of D shows smaller values for the emission lines/continuum ratio and a larger equivalent width for absorption features located in the blueshifted P Cygni profile. The possible explanations of these observations are briefly discussed in terms of micro-lensing and/or intrinsic variability of the source. [less ▲]

A search for gravitational lensing among highly luminous quasars - New results

in Mellier, Y.; Fort, B.; Soucail, G. (Eds.) Gravitational Lensing (1990)

Images of highly luminous QSOs are analyzed to determine whether the gravitational magnification of the background QSO by matter associated with the foreground galaxies accounts for the excess of galaxies ... [more ▼]

Images of highly luminous QSOs are analyzed to determine whether the gravitational magnification of the background QSO by matter associated with the foreground galaxies accounts for the excess of galaxies in the fields of distant QSOs. Galaxy detection is increased by utilizing red-filter images, 40 taken with the EFOSC at the ESO 3.6-m telescope and 43 taken with a direct CCD camera at the ESO/MPI 2.2-m telescope. The R-magnitude ranges from 22.5 to 23.0 for the sample, for which the number of galaxies is counted by eye, showing 45 galaxies of radio and optical type. The overdensity found is not as pronounced as that of Fugmann (1988) or that of Webster et al. (1988). A systematic subtraction of the point spread function is also described to investigate the idea that some galaxies responsible for the QSO light magnification are within the inner 3-arcsec circle. The galaxies very close to the line-of-sight are theorized to contribute significantly to the magnification of these QSOs. [less ▲]

Two more very massive stars resolved

in Astronomy and Astrophysics (1989), 222

New evidence against the existence of very massive stars in the Magellanic Clouds is presented. Using high resolution CCD images and appropriate image restoration methods, it is shown that Sk 157 and Sk ... [more ▼]

New evidence against the existence of very massive stars in the Magellanic Clouds is presented. Using high resolution CCD images and appropriate image restoration methods, it is shown that Sk 157 and Sk-69 deg 253, lying in the SMC and LMC, respectively, are not single, very massive, but multiple systems. Thus, two of the most massive stars in existence, with the estimated masses of about 85 solar masses and greater than 120 solar masses vanish from astronomy. The results presented here have important implications for star formation models and the extragalactic distance scale. [less ▲]

New evidence against the existence of very massive stars

in Astronomy and Astrophysics (1988), 201

The most luminous stars are our first probes for exploring the stellar content of distant galaxies. They have also been used as standard candles for extragalactic distance determinations. The authors show ... [more ▼]

The most luminous stars are our first probes for exploring the stellar content of distant galaxies. They have also been used as standard candles for extragalactic distance determinations. The authors show that Sk -66°41, one of the brightest stars in the Large Magellanic Cloud (LMC), is a multiple system consisting of at least six components. This result has important consequences for the understanding of star formation mechanisms, especially the upper limit to stellar masses. Moreover, when primary distance indicators are not available, care should be taken in using the brightest blue stars. The derived distances, depending on the number of cluster members, can easily be underestimated by more than a factor 2, leading to larger values for the Hubble constant. [less ▲]