Not Available

Time-distance analysis is emerging as a powerful diagnostic tool in local helioseismology. By directly measuring propagation times of wave packets between selected locations at the surface of the sun, and their variations over specific areas, a directed diagnostic of the physical properties of the region below these areas can be achieved. We

Photometric optical data of QSO 0957+561 covering the period 1984-1999 are analyzed to discern between the two values of the time delay (417 and 424 days) mostly accepted in the recent literature. The observations, performed by groups from three different institutions-Princeton University, Harvard-Smithsonian Center for Astrophysics, and Instituto

Broad-band optical observations of the extraordinarily bright optical afterglow of the intense gamma-ray burst GRB 991208 started ~2.1 days after the event and continued until 4 Apr. 2000. The flux decay constant of the optical afterglow in the R-band is -2.30 +/- 0.07 up to ~5 days, which is very likely due to the jet effect, and it is followed by

In this poster we present the results from the multi-wavelength study of the dynamical and photometric evolution of the Blue Compact Dwarf galaxy Mrk 86. We have obtained BVRJHK, Hα , and [Oiii]λ 5007 Å imaging, long-slit optical spectroscopy, and Hα Fabry-Perot interferometry for this galaxy. These observations will be complemented in a near

An analytical model has been developed to empirically study the effects of stellar spots and faculae on the observed equivalent widths of Li i 6708, Na i 5896 and K i 7699 Å lines (and abundances in the case of lithium) in late-type stars, taking into account the changes in the observed magnitudes and colors. Solar spectra corresponding to