Damien Hutsemekers

An optical time-delay for the lensed BAL quasar HE 2149-2745

We present optical V and i-band light curves of the gravitationally lensed BAL quasar HE 2149-2745. The data, obtained with the 1.5 m Danish Telescope (ESO-La Silla) between October 1998 and December 2000, are the first from a long-term project aimed at monitoring selected lensed quasars in the Southern Hemisphere. A time delay of 103+/-12 days is determined from the light curves. In addition, VLT/FORS1 spectra of HE 2149-2745 are deconvolved in order to obtain the spectrum of the faint lensing galaxy, free of any contamination by the bright nearby two quasar images. By cross-correlating the spectrum with galaxy-templates we obtain a tentative redshift estimate of z=0.495+/-0.01. Adopting this redshift, a Omega =0.3, Lambda =0.7 cosmology, and a chosen analytical lens model, our time-delay measurement yields a Hubble constant of H0=66 +/- 8 km s-1 Mpc-1 (1sigma error) with an estimated systematic error of +/-3 km s-1 Mpc-1. Using non-parametric models yields H0=65 +/- 8 km s-1 Mpc-1 (1sigma error) and confirms that the lens exhibits a very dense/concentrated mass profile. Finally, we note, as in other cases, that the flux ratio between the two quasar components is wavelength dependent. While the flux ratio in the broad emission lines - equal to 3.7 - remains constant with wavelength, the continuum of the brighter component is bluer. Although the data do not rule out extinction of one quasar image relative to the other as a possible explanation, the effect could also be produced by differential microlensing by stars in the lensing galaxy.

The Clover Leaf Quasar H1413+117: New Photometric Light Curves

Direct CCD images of the gravitationally lensed BAL quasar H1413+117 (Bessel B, V, R, I; Gunn r and i), obtained during 1989−1994 in the framework of photometric monitorings at ESO and with the NOT, have been carefully (re-)analyzed. Simultaneous fitting of 4 PSFs, fixing the relative positions of components B, C and D with respect to A, has been achieved successfully. The relative light curves of the 4 lensed QSO images, with respect to a stable nearby comparison star, confirm the general trend already presented by Arnould et al. (1993). The amplitude of the light curves is found to be about 0.5 magnitude, peak-to-peak in the V filter. The four lensed components display brightness variations quasi-simultaneously and in parallel. In addition to these intrinsic light variations due to the source, we find that component D shows extra light variations with respect to the other components. These are very likely caused by micro-lensing.

New arguments supporting the intrinsic origin of BAL QSOs - Formation of the complex Ly-alpha+NV line profile

In order to further elucidate the question whether all quasars are affected by the BAL phenomenon, we investigate the possibility that observed BAL profiles are formed in spherically symmetric expanding atmospheres.