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V838 Mon has undergone one of the most mysterious stellar outbursts on record. The spectrum at maximum closely resembled a cool AGB star, evolving toward cooler temperatures with time, never reaching optically thin conditions or showing increasing ionization and a nebular stage. The latest spectral type recorded is M8-9. The amplitude peaked at ΔV

We present high-time-resolution spectroscopy of the non-eclipsing old nova V533 Herculis (N Her 1963). It is the second nova remnant affected by the `SW Sex syndrome'. A modulation of the equivalent width of the emission lines with a period of 23.33 min has been detected. This, together with the strong He IIλ4686 emission characteristic of magnetic

From the peak of a gravitational microlensing high-magnification event in the A component of QSO 2237+0305, which was accurately monitored by the Gravitational Lenses International Time Project collaboration, we derived new information on the nature and size of the optical V-band and R-band sources in the distant quasar. If the microlensing peak is

We have studied the host galaxies of a sample of radio-loud active galactic nuclei (AGNs) spanning more than 4 decades in the energy output of the nucleus. The core sample includes 40 low-power sources (BL Lac objects) and 22 high-power sources (radio-loud quasars) spanning the redshift range 0.15

We analyze Space Telescope Imaging Spectrograph (STIS) spectra in the 1150-1700 Å wavelength range obtained for six early B supergiants in the neighboring galaxy M31. Because of their likely high (nearly solar) abundance, these stars were originally chosen to be directly comparable to their Galactic counterparts and represent a much needed addition