Search Publications
Detection of mid-infrared aromatic hydrocarbon emission features from the Small Magellanic Cloud
Boulanger, F.; Reach, W. T.; Contursi, A. +1 more
The mid-infrared (5-16 mu m) spectral energy distribution for an individual quiescent molecular cloud in the Small Magellanic Cloud (SMC) was observed using ISOCAM. The spectrum is dominated by broad emission bands at 6.2, 7.7, and 11.3 mu m, with weaker bands at 8.6 and 12.7 mu m. As these are the same bands, with similar shape and relative stren…
Magnetic structure of overexpanding coronal mass ejections: Numerical models
Cargill, Peter J.; Schmidt, Joachim; Spicer, D. S. +1 more
Numerical simulations are presented of the evolution of overexpanding coronal mass ejections (OCMEs), which are also magnetic clouds. The OCME is assumed to arise from the evolution of a magnetic flux rope with high plasma and magnetic pressure and high plasma density near the Sun in a high-speed solar wind. It is shown that the flux rope maintain…
Jupiter's hydrocarbons observed with ISO-SWS: vertical profiles of C_2H_6 and C_2H_2, detection of CH_3C_2H
Lellouch, E.; Encrenaz, T.; Feuchtgruber, H. +3 more
We have analysed the ISO-SWS spectrum of Jupiter in the 12-16 mum range, where several hydrocarbons exhibit rovibrational bands. Using temperature information from the methane and hydrogen emissions, we derive the mixing ratios (q) of acetylene and ethane at two independent pressure levels. For acetylene, we find q=(8.9+1.1-0.6
A Search for OH Megamasers at Z > 0.1. I. Preliminary Results
Giovanelli, Riccardo; Darling, Jeremy
We present the preliminary results of a survey for OH megamasers underway at the Arecibo Observatory.1 The goals of the survey are to calibrate the luminosity function of OH megamasers to the low-redshift galaxy merger rate (0.1<z<0.2) and to use the enhanced sample of OH megamasers provided by the survey to study OH megamaser environments, …
Adaptive optics images at 3.5 and 4.8 µ m of the core arcsec of NGC 1068: more evidence for a dusty/molecular torus
Alloin, D.; Marco, O.
Adaptive optics observations of NGC 1068 have allowed us to reach with a 4 m class telescope, diffraction-limited images at 3.5 µm (FWHM=0.24'') and 4.8 µm (FWHM=0.33'') of the central arcsec region. These observations reveal the presence of an unresolved core (radius less than 8 pc at Half Maximum) and an 80 pc sized ``disc-like'' str…
Spiral Structure as a Recurrent Instability
Sellwood, J. A.
A long-standing controversy in studies of spiral structure has concerned the lifetimes of individual spiral patterns. Much theoretical work has sought quasi-stationary spiral modes while N-body simulations have consistently displayed recurrent, short-lived patterns. The simulations manifest a recurrent cycle of true instabilities related to small-…
What Do the Ultraviolet Spectra of Narrow-Line Seyfert 1 Galaxies Tell Us about Their Broad-Line Regions?
Wilkes, Belinda J.; Mathur, Smita; Czerny, Bożena +1 more
We study the UV spectra of narrow-line Seyfert 1 (NLSy1) galaxies and compare them with ``normal'' active galactic nuclei. Similar to their optical lines, the NLSy1s show narrower UV lines. They are also characterized by weaker C IV λ1549 and C III] λ1909 and stronger Al III λ1857 emission. These UV-line properties add to the optical and X-ray pro…
Nearby Microlensing Events: Identification of the Candidates for theSpace Interferometry Mission
Gould, Andrew; Salim, Samir
The Space Interferometry Mission (SIM) is the instrument of choice when it comes to observing astrometric microlensing events where nearby, usually high proper motion, stars (``lenses'') pass in front of more distant stars (``sources''). Each such encounter produces a deflection in the source's apparent position that, when observed by SIM, can lea…
Observation of the origin of CMEs in the low corona
Delaboudinière, J. -P.; Lamy, P.; Delannée, C.
The aim of the main observing program with EIT on board SOHO, is to monitor the whole Sun surface in the Fe xii emission line at 195 Ä, every 17 minutes. The very beginning of some CMEs can be observed. We interpret Fe xii images in conjunction with He ii, Hα and coronagraph observations over a period of 6 days. We find that 7 prominences produced…
HUBBLE SPACE TELESCOPE Observations of the Host Galaxy of GRB 970508
Pian, E.; Palazzi, E.; Frontera, F. +13 more
We report on observations of the field of GRB 970508 made in 1998 early August, 454 days after outburst, with the STIS CCD camera on board the Hubble Space Telescope (HST). The images, taken in open filter (50CCD) mode, clearly reveal the presence of a galaxy that was overwhelmed in earlier (1997 June) HST images by emission from the optical trans…