Search for optical bursts from the gamma ray burst source GBS 0526-66

Attempts were made to detect optical bursts from the gamma-ray burst source GBS 0526-66 during Dec. 31, 1984 to Jan. 2, 1985 and Feb. 23 to Feb. 24, 1985, using the one meter reflector of the Kavalur Observatory. Jan. 1, 1985 coincided with the zero phase of the predicted 164 day period of burst activity from the source (Rothschild and Lingenfelter, 1984). A new optical burst photon counting system with adjustable trigger threshold was used in parallel with a high speed photometer for the observations. The best time resolution was 1 ms and maximum count rate capability was 255,000 counts s(-1). Details of the instrumentation and observational results are presented

Studies on the hepatic and renal status of patients with sickle cell disease from western zone of Maharashtra, India

Background: Sickle cell disease (SCD) is the most common inherited monogenic genetic disorder in Indian tribal and non-tribal population. This condition is caused by mutations in the hemoglobin gene and inherited in an autosomal recessive pattern. Pathogenesis in SCD varies widely from patient to patient. Most of the infections affect SCD pathogenesis, so early diagnosis of the same is important.Methods: The present study was designed to evaluate the biochemical parameters to assess the hepatic and renal status in SCD subjects from west zone of Maharashtra, India. Patients with sickle cell disease (n=50) from primary health centres of Palghar were included in this study and age and sex matched healthy persons (n=50) were controls. Informed written consent was obtained from all the study subjects.Results: Our findings showed that Aspartate trasaminase (AST), Alanine transaminase (ALT), bilirubin and creatinine increased significantly above normal level in SCD subjects. Albumin and urea levels in SCD were found to have decreased in the SCD subjects. There is a slight increase in uric acid and creatinine levels; this indicates an adverse effect on hepatic function and moderate effect on renal function in sickle cell anemia patients. Most common events of SCD pathogenesis, can be categorized into hemolytic events and vaso-occlusive crisis-based events. Adverse effect on hepatic function can lead to further hemolytic events.Conclusions: Although specific biomarkers related to these different events needs to understand for assessment of pathogenesis, the ones we have studied can be useful to assess the status of hepatic and renal function to follow the effectiveness of therapeutic interventions.

Voyager 2 and the world of Neptune

After dramatic discoveries during its flybys of Jupiter, Saturn and Uranus, Voyager 2 has now sent back breath- taking images of Neptune and its moons. The major discoveries in the Neptunian system include puzzling weather systems, broad sheet of ring material, peculiar offset and tilting of the magnetic dipole field, six new moons, and atmospheric composition and surface features of the biggest moon, Triton

High speed photometry of PG 1012-029

High speed optical photometric observations of PG 1012-029, conducted during 1990-1991, confirm the nova-like classification of the object. Several eclipses observed by us have been used to refine the orbital period of the system. Variations in the light curves and in particular, the presence of a bright hot spot in our 1991 data are high-lighted. We also deduce a maximum mass transfer rate of 1.5 10-8M⊙ yr-1 for the system

The Interplanetary Network Supplement to the BeppoSAX Gamma-Ray Burst Catalogs

Between 1996 July and 2002 April, one or more spacecraft of the interplanetary network detected 787 cosmic gamma-ray bursts that were also detected by the Gamma-Ray Burst Monitor and/or Wide-Field X-Ray Camera experiments aboard the BeppoSAX spacecraft. During this period, the network consisted of up to six spacecraft, and using triangulation, the localizations of 475 bursts were obtained. We present the localization data for these events.Comment: 89 pages, 3 figures. Submitted to the Astrophysical Journal Supplement Serie

Flares on AM Canum Venaticorum

AM CVn, an interacting binary system consisting of two helium white dwarfs, has been classified as a nova-like object. Normally it exhibits only small amplitude modulations of 0.05 mag with a 1051 s periodicity. The authors report what is believed to be for the first time, two unusually intense optical flares in AM CVn during 1985-87. The characteristics of the two flares in white light observed on 1985 February 24 and 1986 February 7 with Δm=0.34 and Δm=1.07 respectively are described. The authors estimate the maximum amount of energy released from these flares as 2.7×1036 erg and suggest in the light of current models possible sites of origin of the flaring activity

Understanding the Cool DA White Dwarf, G29-38

The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post main sequence evolution, along with their cooling rates, allowing us to calibrate their ages directly. The most important set of white dwarf variables to measure are the oldest of the pulsators, the cool DAVs, which have not previously been explored through asteroseismology due to their complexity and instability. Through a time-series photometry data set spanning ten years, we explore the pulsation spectrum of the cool DAV, G29-38 and find an underlying structure of 19 (not including multiplet components) normal-mode, probably l=1 pulsations amidst an abundance of time variability and linear combination modes. Modelling results are incomplete, but we suggest possible starting directions and discuss probable values for the stellar mass and hydrogen layer size. For the first time, we have made sense out of the complicated power spectra of a large-amplitude DA pulsator. We have shown its seemingly erratic set of observed frequencies can be understood in terms of a recurring set of normal-mode pulsations and their linear combinations. With this result, we have opened the interior secrets of the DAVs to future asteroseismological modelling, thereby joining the rest of the known white dwarf pulsators.Comment: 29 pages including 5 figures To appear in ApJ 1 Mar 9

New Whole Earth Telescope observations of CD-24 7599: steps towards δ Scuti star seismology

92 h of new Whole Earth Telescope observations have been acquired for the δ Scuti star CD-24 7599. All the seven pulsation modes reported by Handler et al. are confirmed. However, significant amplitude variations which are not caused by beating of closely spaced frequencies occurred within two years. Analysing the combined data of both WET runs, we detect six further pulsation modes, bringing the total number up to 13. We also examine our data for high-frequency pulsations similar to those exhibited by rapidly oscillating Ap stars, but we do not find convincing evidence for variability in this frequency domai