On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.

We present precise optical and near-infrared ground-based photometry of two Globular Clusters (GCs): ω Cen and 47 Tuc. These photometric catalogs are unbiased in the Red Giant Branch (RGB) region close to the tip. We provide new estimates of the RGB tip (TRGB) magnitudesm I (T RGB) = 9.84 ± 0.05, ω Cen; m I (T RGB) = 9.46 ± 0.06, 47 Tuc-and use these to determine the relative distances of the two GCs. We find that distance ratios based on different calibrations of the TRGB, the RR Lyrae stars and kinematic distances agree with each other within one sigma. Absolute TRGB and RR Lyrae distance moduli agree within 0.10-0.15 mag, while absolute kinematic distance moduli are 0.2-0.3 mag smaller. Absolute distances to 47 Tuc based on the Zero-Age-Horizontal-Branch and on the white dwarf fitting agree within 0.1 mag, but they are 0.1-0.3 mag smaller than TRGB and RR Lyrae distances. Subject headings: globular clusters: ω Centauri, 47 Tucanae 1 Based on observations made with ESO telescopes SOFI@NTT, La Silla; ISAAC@VLT Paranal, projects: 66.D-0557, 68.D-0545, 075.D-0824, 79.D-0765 and on images obtained from the ESO/ST-ECF. Optical data were also collected with the 1.0m SAAO telescope, projects: 2006.1.012, 2006.2.02.

No abstract

We report optical and near-infrared follow-up observations of GRB 011121 collected predominantly at ESO telescopes in Chile. We discover a break in the afterglow light curve after 1.3 days, which implies an initial jet opening angle of about 9 . The jet origin of this break is supported by the fact that the spectral energy distribution is achromatic during the first 4 days. During later phases, GRB 011121 shows significant excess emission above the flux predicted by a power law, which we interpret as additional light from an underlying supernova. In particular, the spectral energy distribution of the optical transient approximately 2 weeks after the burst is clearly not of power-law type but can be presented by a blackbody with a temperature of $6000 K. The deduced parameters for the decay slope and the spectral index favor a wind scenario, i.e., an outflow into a circumburst environment shaped by the stellar wind of a massive gamma-ray burst (GRB) progenitor. Because of its low redshift of z ¼ 0:36, GRB 011121 has been the best example for the GRB-supernova connection until GRB 030329 and provides compelling evidence for a circumburster wind region expected to exist if the progenitor was a massive star.

Aims. We present time-resolved photometry of five relatively poorly-studied cataclysmic variables: V1193 Ori, LQ Peg, LD 317, V795 Her, and MCT 2347-3144. Methods. The observations were made using four 1m-class telescopes for a total of more than 250 h of observation and almost 16 000 data points. For LQ Peg WHT spectroscopic data have been analysed as well. Results. The light curves show a wide range of variability on different time scales from minutes to months. We detect for the first time a brightness variation of 0.05 mag in amplitude in V1193 Ori on the same timescale as the orbital period, which we interpret as the result of the irradiation of the secondary. A 20-min quasi-periodic oscillation is also detected. The mean brightness of the system has changed by 0.5 mag on a three-month interval, while the flickering was halved. In LQ Peg a 0.05 mag modulation was revealed with a period of about 3 h. The flickering was much smaller, of the order of 0.025 mag. A possible quasi-periodic oscillation could exist near 30 min. For this object, the WHT spectra are single-peaked and do not show any radial-velocity variations. The data of LD 317 show a decrease in the mean magnitude of the system. No periodic signal was detected but this is certainly attributable to the very large flickering observed: between 0.07 and 0.1 mag. For V795 Her, the 2.8-h modulation, thought to be a superhump arising from the precession of the disc, is present. We show that this modulation is not stable in terms of periodicity, amplitude, and phase. Finally, for MCT 2347-3144, a clear modulation is seen in a first dataset obtained in October 2002. This modulation is absent in August 2003, when the system was brighter and showed much more flickering.

Context. On 4 July 2005 at 05:52 UT, the impactor of NASA's Deep Impact (DI) mission crashed into comet 9P/Tempel 1 with a velocity of about 10 km s −1 . The material ejected by the impact expanded into the normal coma, produced by ordinary cometary activity. The La Silla and Paranal sites of the European Southern Observatory (ESO) in Chile participated in the world-wide campaign to observe this event.Aims. Based on visible and near-IR observations of the comet, the characteristics and the evolution with time of the cloud of solid particles released by the impact is studied in order to gain insight into the composition of the nucleus of the comet. Also, an analysis of solid particles in the coma not related to the impact was also performed. Methods. The characteristics of the non-impact coma and cloud produced by the impact were studied by observations in the visible wavelengths, using narrow band filters with passbands free of gas emission, and in the near-IR. The scattering characteristics of the "normal" coma of solid particles were studied by comparing images in various spectral regions, from the UV to the near-IR. For each filter, an image of the "normal" coma was then subtracted from images obtained in the period after the impact, revealing the contribution of the particles released by the impact. Comparison of the images of the cloud recorded in the various filters provides some ideas about the composition of the particles and their evolution. Results. For the non-impact coma the Afρ, a proxy of the dust production, has been measured in various spectral regions. The presence of sublimating grains, which scatter very efficiently in the near-IR, has been detected. Their lifetime was found to be of the order of 11 h. Regarding the cloud produced by the impact, the total geometric cross section multiplied by the albedo, SA, was measured as a function of the color and time. From the expansion of the cloud, the projected velocity was studied. It appeared to obey a Gaussian distribution with the average velocity of the order of 115 m s −1 . By comparing the observations taken 3 h apart, about 20 h after the impact, we have found a strong decrease in the cross section in J filter, while that in K s remained almost constant. This is interpreted as the result of sublimation of grains dominated by particles of sizes of the order of some microns.

No abstract

No abstract