Search Publications

A model of the stellar radiation field in the UV.

Henry, R. C.; Murthy, Jayant; Sujatha, N. V. +1 more

This work is the first step in a systematic effort to understand and predict the different components of the UV (912 A - 3000 A) radiation field over the entire sky. We have developed a model to predict the ISRF in the UV within a few hundred parsecs of the Sun using the Hipparcos star catalog. We have checked the model through a comparison with t…

Mid-infrared sources in the ELAIS Deep X-ray Survey

Franceschini, A.; Vaccari, M.; Serjeant, S. +9 more

We present a cross-correlation of the European Large Area Infrared Space Observatory (ISO) survey (ELAIS) with the ELAIS Deep X-ray Survey of the N1 and N2 fields. There are seven Chandra point sources with matches in the ELAIS Final Analysis 15-µm catalogue, out of a total of 28 extragalactic ISO sources present in the Chandra fields. Five …

Limits on the Optical Brightness of the ɛ Eridani Dust Ring

Calzetti, Daniela; Livio, Mario; Gull, Theodore R. +10 more

The STIS CCD camera on the Hubble Space Telescope (HST) was used to take deep optical images near the K2 V main-sequence star ɛ Eridani in an attempt to find an optical counterpart of the dust ring previously imaged by submillimeter observations. Upper limits for the optical brightness of the dust ring are determined and discussed in the context o…

VLT FORS-1 observations of NGC 6397: Evidence for mass segregation

Testa, V.; Marconi, G.; Buonanno, R. +3 more

We present (V, V-I) VLT-FORS1 observations of the Galactic Globular Cluster NGC 6397. We derive accurate color-magnitude diagrams and luminosity functions (LFs) of the cluster Main Sequence (MS) for two fields extending from a region near the centre of the cluster out to ≃10 arcmin. The photometry of these fields produces a narrow MS extending dow…

The Enigmatic Radio Source T Tauri S

Hummel, C. A.; Thomasson, P.; Johnston, K. J. +4 more

We have observed the T Tau multiple star system using the Multielement Radio-linked Interferometer Network at a frequency of 5 GHz. The compact centimeter wavelength radio emission from T Tau S has been found to consist of at least two components separated by approximately 70 mas in right ascension at Julian epoch 2001.89. Using this data and that…

Inference of hot star density stream properties from data on rotationally recurrent DACs

Owocki, S. P.; Kaper, L.; Hamann, W. -R. +5 more

The information content of data on rotationally periodic recurrent discrete absorption components (DACs) in hot star wind emission lines is discussed. The data comprise optical depths τ(w,φ) as a function of dimensionless Doppler velocity w=(Δλ/λ₀)(c/v_&infy) and of time expressed in terms of stellar rotation angle φ. This…

Submillimeter Emission from Type Ia Supernova Host Galaxies at z = 0.5

Farrah, D.; Fox, M.; Rowan-Robinson, M. +2 more

We present deep submillimeter observations of 17 galaxies at z=0.5 that are hosts of a Type Ia supernova. Two galaxies are detected directly, and the sample is detected statistically with a mean 850 µm flux of 1.01+/-0.33 mJy, which is 25%-135% higher than locally. We infer that the mean value of A_V in normal galaxies at z=0.5 is …

A high-resolution study of the interstellar medium in the luminous IRAS galaxy Arp 193

Clemens, M. S.; Alexander, P.

We present high-resolution multi-element radio-linked interferometer network (MERLIN) and Very Large Array (VLA) observations of the H I absorption towards the starburst nucleus of Arp 193 (IC 883, UGC 08387), a luminous IRAS merger. We compare the distribution of atomic gas with that of radio continuum emission, high-resolution CO data and near-i…

The Solar and Interplanetary Causes of Space Storms in Solar Cycle 23

Bothmer, V.

SOHO CDS and SUMER observations of quiescent filaments and their interpretation

Parenti, S.; Del Zanna, G.; Chiuderi Drago, F.

Three quiescent filaments located at different positions on the solar disk were selected from the SOHO CDS data archive: one of them was also observed by SUMER in the raster mode. We investigate the filament-corona transition region (PCTR) emission, to determine whether it is indeed negligible, as found in one previously-analysed case. The observa…