Search Publications
The Nature of the Far-Infrared Emission from Seyfert Galaxies
Pérez García, A. M.; Rodríguez Espinosa, J. M.
Optical R-band imaging data and far-infrared (FIR) Infrared Space Observatory data from Seyfert galaxies are combined to show that the compact optical emission from the nuclear and circumnuclear region correlates reasonably well with the warm FIR emission that is observed in these objects, while the extended optical emission, which essentially ori…
A photometric and spectroscopic study of the association LH47 in the superbubble N44 in the LMC
Bomans, D. J.; Dieball, A.; Will, J. -M.
The OB association LH47 inside the superbubble N44 in the Large Magellanic Cloud (LMC) is analyzed with CCD photometry. For the bright blue stars spectra in the optical and UV have been taken. The observed U, B, and V magnitudes and colours are converted to Teff and L. From isochrone fits to the colour magnitude diagram (CMD), we find a…
The dust sensor for CASSINI
Grün, Eberhard; Srama, Ralf
In October 1997 a unique mission to the Saturnian system will be launched by NASA, the CASSINI mission. One goal of this mission is to study the Saturnian dust environment, and for this task, the COSMIC DUST ANALYZER (CDA) has been developed and is currently under test. Impact ionization is used to determine the speed (1 - 100 km/s) and the mass (…
The Hardness-Intensity Correlation in Bright Gamma-Ray Bursts
Hurley, K.; Sunyaev, R.; Boer, M. +10 more
The presence of a hardness-intensity correlation (HIC) is demonstrated in a sample of 77 bright bursts observed by the Phebus and Ulysses gamma-ray burst (GRB) experiments. Using simulations, we find a significant correlation (5 σ) between the peak spectral hardness and the peak intensity in Phebus. Moreover, the HIC is compatible with a single re…
Mid-infrared spectroscopy of the hyperluminous infrared galaxy IRAS P09104+4109.
Kawara, K.; Murayama, T.; Taniguchi, Y. +2 more
We present mid-infrared spectroscopy of the hyperluminous infrared galaxy IRAS 09104+4109 based on observations with ISOCAM CVF. We have detected the emission peak around 8µm as well as the absorption feature around 10µm possibly due to silicate, providing evidence for a dusty torus around the central engine. Comparing the observationa…
ISOCAM Observations of the Comet P/Kopff Dust Trail
Reach, William T.; Boulanger, Francois; Sykes, Mark V. +3 more
We present the results of two scans through the dust trail of Comet P/Kopff made with ISOCAM on 26 March 1996. Positions behind the comet at mean anomalies of 0.5° and 1° less than the nucleus were imaged using the LW10 (IRAS Band 1, 12 µm) filter. The trail is clearly detected and appears to have varied since it was observed with the IRAS s…
Rest-frame variability of quasars and Seyfert galaxies in the ultraviolet: constraints on the discrete-event models.
Paltani, S.; Courvoisier, T. J. -L.
A study of the ultraviolet continuum variability (Paltani & Courvoisier, 1994A&A...291...74P) has shown that the relative variability of quasars and Seyfert galaxies decreases when the luminosity increases. The spectral information included in the IUE spectra allows us to study this dependence in the rest frame of the objects. The trend is…
Effects of Non-LTE Radiative Loss and Partial Ionization on the Structure of the Transition Region
Chae, J.; Yun, H. S.; Poland, A. I.
In this paper we address the question of how non-LTE radiative losses with partial ionization of hydrogen and helium affects the energetics and structure of the solar transition region. To accomplish this we have constructed theoretical models of a thin rigid magnetic flux tube with a steady material flow, which is embedded vertically in the solar…
Cassini/Huygens Science Instruments, Spacecraft, and Mission
Jaffe, Leonard D.; Herrell, Linda M.
Hubble Space Telescope Imaging of the Host Galaxies of Three X-Ray-selected BL Lacertae Objects
Yanny, Brian; Jannuzi, Buell T.; Impey, Chris
Hubble Space Telescope (HST) WFPC-2 I-band (F814W) images of three X-ray-selected BL Lacertae objects (MS 1221.8+2452, MS 1407.9+5954, and MS 2143.4+0704) reveal that each of these BL Lac objects is well centered in an extended nebulosity that is consistent in brightness and morphology with light from an elliptical galaxy at their previously repor…