Context. One of the most distinctive features in active galactic nuclei (AGN) is the variability of their emission. Variability has been discovered at X-ray, UV, and radio frequencies on timescales from hours to years. Among the AGN family and according to theoretical studies, low-ionization nuclear emission line region (LINER) nuclei would be

The ROSAT X-ray observations were carried out at three different epochs between 1992 and 1996. Two PSPC (called "A" and "B") and one HRI ("H") observations were scheduled on NGC 2451. (3 data files).

Context. Active galactic nuclei (AGN), powered by accretion onto supermassive black holes (SMBHs), are thought to be scaled up versions of Galactic black hole X-ray binaries (BH-XRBs). In the past few years evidence of such correspondence include similarities in the broadband shape of the X-ray variability power spectra, with characteristic bend

We have been regularly monitoring the outburst decay of the black hole candidate X-ray binary XTE J1752-223 (discovered by RXTE; ATel #2258) with the 2-m Faulkes Telescopes North and South (located at Haleakala on Maui and Siding Spring, Australia, respectively). Exposures in B, V, R and i'-bands (mostly 100-sec exposures each) were taken every ~ 3

We observed the black hole candidate XTE J1752-223 (ATel #2258) with the William Herschel Telescope (WHT) and the ACAM imager/spectrograph at the Observatorio del Roque de los Muchachos, La Palma, Spain. 200-s exposures were taken in the R and I bands under photometric conditions and 0.6-0.7-arcsec seeing on Aug 24.887 and Aug 24.893, respectively

IAUC 7000 available at Central Bureau for Astronomical Telegrams.