Related papers: On the optical extinction and distance of GRS 1915…
Millimeter observations of the galactic source of relativistic ejections GRS 1915+105 (Mirabel & Rodriguez 1994) are consistent with this source being at a kinematic distance D = 12.5 +/- 1.5 kpc from the Sun, behind the core of a molecular…
A linear relation between the hydrogen column density (N_H) and optical extinction (A_V) in the Galaxy has long been observed. A number of studies found differing results in the slope of this relation. Here, we utilize the data on 22…
We investigate the relation between the optical extinction ($A_V$) and the hydrogen column density ($N_H$) determined from X-ray observations of a large sample of Galactic sightlines toward 35 supernova remnants, 6 planetary nebulae, and 70…
We derive the extinction curve towards the Galactic Center from 1 to 19 micron. We use hydrogen emission lines of the minispiral observed by ISO-SWS and SINFONI. The extinction free flux reference is the 2 cm continuum emission observed by…
We refine a classic relation between the hydrogen column density (NH) and optical extinction (Av) by employing 39 Galactic Supernova Remnants (SNRs) with X-rays, optical and/or infra-red data available. We find NH = (1.69+/-0.07)*10^21 Av…
We present a comprehensive study of interstellar X-ray extinction using the extensive Chandra supernova remnant archive and use our results to refine the empirical relation between the hydrogen column density and optical extinction. In our…
Hydrogen column densities inferred from X-ray absorption are typically 5 - 30 times larger than the neutral atomic hydrogen column densities derived from 21cm HI absorption toward radio-loud active galactic nuclei. Some part of the…
We put stringent constraints for the first time on the dust properties in the circumburst medium of a gamma-ray burst (GRB) afterglow. This is based on the optical spectrum of GRB 020813 (z=1.255), obtained with Keck I LRIS 4.65 h after the…
We report on the abundance of interstellar neutral nitrogen (NI) for 30 sightlines, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Hubble Space Telescope (HST). NI column densities are derived by measuring the…
We aim to compare variations in the full-UV dust extinction curve (912-3000 Angstrom), with the HI/H$_2$/total H content along diffuse Milky Way sightlines, to investigate possible connections between ISM conditions and dust properties. We…
A search for radio recombination lines near 20 cm at z=0.193 and z=0.886 towards the gravitational lens system PKS 1830-211 has yielded upper limits on the line optical depth of 5 x 10^{-5} and 5 x10^{-4} at the two redshifts respectively.…
The gas-to-dust ratio of reddened stars in the Milky Way (MW), the Magellanic Clouds, and in general is usually expressed as a linear relation between the hydrogen column density, N(H), and the reddening, E(B-V), or extinction in the V band…
We present optical and near-infrared observations of the dim afterglow of GRB 020124, obtained between 2 and 68 hours after the gamma-ray burst. The burst occurred in a very faint (R > 29.5) Damped Ly-alpha Absorber (DLA) at a redshift of z…
The 21 cm hyperfine transition of the atomic hydrogen (HI) in ground state is a powerful probe of the neutral gas content of the universe. This radio frequency transition has been used routinely for decades to observe, both in emission and…
We report the first ensemble results from the FUSE survey of molecular hydrogen in lines of sight with A_V $\gtrsim$ 1 mag. We have developed techniques for fitting computed profiles to the low-J lines of H2, and thus determining column…
We report total abundances and related parameters for the full sample of the FUSE survey of molecular hydrogen in 38 translucent lines of sight. New results are presented for the "second half" of the survey involving 15 lines of sight to…
Despite the vastly different angular scales on which they are measured, the integrated $\lambda$21 cm \HI\ optical depth measured interferometrically, \WHI, is a good proxy for the optical reddening derived from IR dust emission, with…
We present column density measurements of the HD molecule in the interstellar gas toward 17 Galactic stars. The values for the seven most heavily reddened sightlines, with E(B-V) = 0.38-0.72, are derived from observations with the Far…
We present ISO observations of the S(0), S(1), S(2), and S(3) rotational lines of molecular hydrogen from two molecular clouds near the Galactic Center (GC). We have also measured continuum dust emission at infrared wavelengths with ISO and…
We observed the galactic microquasar GRS1915+105 in the K ($2.2 \mu$m) band on October 16 and 17, 1995 UTC using the COB infrared (IR) imager on the Kitt Peak National Observatory 2.1-m telescope with a 0.2-arcsec/pixel plate scale and…