Search Publications
Infrared emission towards SN 1987A 11 years after outburst: Measurements with ISOCAM
Völk, H. J.; Tuffs, R. J.; Fischera, Jg.
We present measurements of the mid-infrared (MIR) emission from SN 1987A, made using the Infrared Space Observatory (ISO) 11 years after outburst. They are the only late epoch detections of this source in the thermal IR regime. The position of the source, determined from an offset to an IR-emitting star, suggests that the emission is associated wi…
The Effect of High-lying Levels on Atomic Models Relevant to Spectroscopic Analyses of Solar Extreme-Ultraviolet Spectra
Bhatia, A. K.; Doschek, G. A.; Feldman, U. +2 more
In this work we investigate the effect of including high-lying configurations in the collisional-radiative models used to calculate spectral line intensities recorded by the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) spectrometer on board the SOHO satellite. Many of the emission lines observed by SUMER are attributed to transitions…
New binary stars discovered by lunar occultations. VI.
Stecklum, B.; Richichi, A.; Calamai, G.
We present additional results from our ongoing lunar occultation program. Observations are presented here for a total of seventeen sources, for the majority of which one or two new companions are detected. The sample comprises mostly field stars, spanning a large range of spectral types. Two infrared objects without optical counterpart are also in…
The Quadruple System µ Orionis: Three-dimensional Orbit and Physical Parameters
Mason, Brian D.; Fekel, Francis C.; McAlister, Harold A. +3 more
The star µ Orionis is a spectroscopic visual quadruple system in which each visual component is a short-period spectroscopic binary. The visual orbit has a period of 18.644 yr, a high eccentricity of 0.7426, and a high inclination of 96.2d. The visual primary consists of an Am star and probably a G or early K dwarf that orbit each other in a…
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868
de Grijs, R.; Santiago, B.; Castro, R. +1 more
Evidence for a second main-sequence turn-off in a deep colour-magnitude diagram (CMD) of NGC 1868 is presented. The data were obtained with Hubble Space Telescope (HST) WFPC2 and reach down to m555~= 25 mag. Besides the usual τ~= 0.8 Gyr turn-off found in previous analyses, another possible turn-off is seen at m555~= 21 mag (…
Models for solar magnetic loops. I. A simple theoretical model and diagnostic procedure
Landini, M.; Landi, E.
In the present paper the quasi-static model of Landini & Monsignori Fossi (\cite{Landini75}) for coronal loops is improved and a simple diagnostic procedure is developed to compare the most important physical properties of the model with a set of spectral observations of loops such as those obtained by the CDS and SUMER instruments on SOHO. Th…
Fragmentation Origin of Major Sungrazing Comets C/1970 K1, C/1880 C1, and C/1843 D1
Sekanina, Zdenek; Chodas, Paul W.
Following our recent successful modeling of the common origin of two of the brightest members of the Kreutz system of sungrazing comets, we now examine three other objects: C/1970 K1 (White-Ortiz-Bolelli), the most recent sungrazer discovered from Earth, C/1880 C1 (Great Southern Comet), and C/1843 D1 (Great March Comet). For White-Ortiz-Bolelli, …
Active longitudes and coronal structures during the rising phase of the solar cycle
Kosovichev, A. G.; Benevolenskaya, E. E.; Scherrer, P. H.
The longitudinal structure of the solar corona has been investigated during the transition period between solar cycles 22 and 23 and at the beginning of the current cycle 23 using the SOHO/EIT data obtained in 171 Å, 195 Å, 284 Å and 304 Å EUV lines. The EIT images were transformed into synoptic maps for each of the spectral lines, and for the 195…
Infrared Space Observatory Short Wavelength Spectrometer Observations of H II Regions in NGC 6822 and I Zwicky 36: Sulfur Abundances and Temperature Fluctuations
Skillman, Evan D.; Garnett, Donald R.; Dinerstein, Harriet L. +1 more
We report Infrared Space Observatory (ISO) Short Wavelength Spectrometer infrared spectroscopy of the H II region Hubble V in NGC 6822 and the blue compact dwarf galaxy I Zw 36. Observations of Brα, [S III] at 18.7 and 33.5 µm, and [S IV] at 10.5 µm are used to determine ionic sulfur abundances in these H II regions. There is relativel…
A Chemically Decoupled Nucleus and Inner Polar Ring of the SBb Galaxy NGC 4548
Sil'chenko, O. K.