Pierre Wallyn

A BATSE Earth Occultation Catalog of 0.03-1.8 MeV Gamma-Ray Source Spectra and Light Curves for Phases 1-3 (1991-1994)

Using the powerful Earth-occultation technique, long-term, nearly continuous monitoring of the entire low-energy gamma-ray sky is now possible with the advent of BATSE, the Burst and Transient Source Experiment on board the Compton Gamma Ray Observatory (CGRO). In this paper, we present a catalog of 34 moderately strong gamma-ray sources measured by BATSE. It consists of 0.03-1.8 MeV photon spectra averaged over weeks and months, and light curves of the 35-200 keV flux, with 1 day resolution, covering the first three phases of the CGRO mission (1991 May through 1994 October). These results have been obtained using the JPL Enhanced BATSE Occultation Package (EBOP) developed under the CGRO Guest Investigator Program. The EBOP concept and approach are also described in some depth. This paper presents highlights extracted from a large EBOP database which has now been archived at the Compton Observatory Science Support Center (COSSC). This database contains a complete record of ~1200 daily source count rates in 14 energy channels along with the corresponding Poisson and systematic errors for 64 sources, including 30 not described here. An interface to XSPEC is included in the archive allowing conversion from count rates to photon fluxes. This paper therefore serves also as a reference and entree into the archive and provides an index and guide for those investigators using the EBOP system and database for their respective scientific investigations.

A new annihilator in the Galactic center region

Following the detection of a possible double backscattered line from 511 keV photons in EXS1737‐2952 (Grindlay et al. 1993) which makes this source a possible new black hole candidate, we searched at radio (mm) wavelengths for a molecular cloud in the vicinity of this source. We detected a cloud very similar to the one associated with 1E1740‐2942. It has the required density (105 cm−3) to annihilate the positrons possibly emitted by EXS and contribute to the Galactic center narrow annihilation line.

Near-infrared observations of GRS 1915+105

During 9 July 1995 and 28 April 1996 we carried out J, H, and Ks observations of the X-ray transient and Galactic black hole candidate GRS 1915+105 using the Cassegrain IR Camera on the 5-meter telescope at Mt. Palomar. Between the two observations the infrared intensity increased by approximately one magnitude to one of the highest levels yet seen, again confirming the highly variable nature of the emission. Our second observation was made during a time when the source was being continuously monitored by CGRO (20–100 keV), RXTE (2–12 keV), and the Ryle Telescope (15 GHz), allowing simultaneous multiwavelength spectra covering a very broad energy range.

Position-sensitive high-resolution spectrometer

A mosaic of high-purity Ge detectors, associated with a mask a few meters above the detector plane, are very promising for future high-energy resolution and source localization astrophysics experiments. This paper describes such a detector and gives its energy resolution vs FET temperature as well as measurements on its localization accuracy. A computer simulation and image reconstruction based on a delta decoding method are also presented.

Mid-infrared spectra of SGR 1806−20 and SGR 1900+14

Two of the three known soft gamma repeaters, SGR 1806−20 and SGR 1900+14, have a fairly small angular separation and are visible from Mt. Palomar. During the nights of 21–23 June 1997 we observed both in the mid-infrared using SpectroCam-10 on the 5-meter Hale telescope. We obtained excellent images of the counterpart to SGR 1900+14 in 6 bands using narrow filters (Δλ∼1 μm) from approximately 8 to 13 μm. The intensities in these 6 bands, summed over the two star-like components of the suspected counterpart, were all ∼2–3 Jy and together yielded the first mid-infrared spectrum of this object. A spectrum of the SGR 1806−20 counterpart was also obtained, but it displayed a significantly different shape and showed a source intensity of only ∼0.1 Jy. When combined with near-infrared and IRAS observations, the spectra imply that the counterparts of both SGRs consist of multiple components at different temperatures.