Search Publications
85 Peg A: what age for a low-metallicity solar-like star?
Cardini, D.; D'Antona, F.; Montalbán, J. +3 more
We explore the possible evolutionary status of the primary component of the binary 85 Pegasi, listed as a target for asteroseismic observations by the MOST satellite. In spite of the assessed `subdwarf' status, and of the accurate distance determination from the Hipparcos data, the uncertainties in the metallicity and age, coupled with the uncerta…
The FERRUM project: experimentally determined metastable lifetimes and transition probabilities for forbidden [TiII] lines observed in η Carinae
Lundberg, H.; Johansson, S.; Hartman, H. +7 more
In the spectrum of an emission-line region ejected from the massive star Eta Carinae, called the strontium filament (SrF), forbidden lines from many elements, in particular [SrII] and [TiII], are observed. These lines are strong in this specific region and valuable for plasma diagnostics. Forbidden lines are not easily produced in laboratory light…
Astrophysical laser operating in the OI 8446-Åline in the Weigelt blobs of η Carinae
Johansson, S.; Letokhov, V. S.
Within the framework of a simple model of photophysical processes in the Weigelt blobs in the vicinity of the luminous blue variable (LBV) star η Carinae, we explain the presence of the fluorescent <OI> 8446-Åand forbidden [OI] 6300-Ålines as well as the absence of the allowed OI 7774-Åline in spectra recorded with the Hubble Space Telescope…
XMM spectroscopy of the transient supersoft source RXJ0513.9 - 6951: probing the dynamic white dwarf photosphere
Charles, P. A.; Heathcote, B.; McGowan, K. E. +3 more
The highly luminous (>1037ergs-1) supersoft X-ray sources (SSSs) are believed to be Eddington-limited accreting white dwarfs undergoing surface hydrogen burning. The current paradigm for SSSs involves thermally unstable mass transfer from a 1-2Msolar companion. However, this model has never been directly confirm…
The cool wake around 4C 34.16 as seen by XMM-Newton
Hardcastle, M. J.; Ponman, T. J.; Stevens, I. R. +3 more
We present XMM-Newton observations of the wake-radio galaxy system 4C 34.16, which shows a cool and dense wake trailing behind the host galaxy of 4C 34.16. A comparison with numerical simulations is enlightening, as they demonstrate that the wake is produced mainly by ram pressure stripping during the galactic motion through the surrounding cluste…
Noise characteristics of full-disc helioseismic observations made by resonant scattering spectrometers
Chaplin, W. J.; Elsworth, Y.; Isaak, G. R. +3 more
Resonant scattering spectrometers (RSSs) have been used to make high-precision full-disc helioseismic observations since the 1970s. They are capable of very high-precision determinations of line-shift, meaning that they are used to obtain precise velocity measurements, and, for suitably configured RSSs, the disc-averaged longitudinal magnetic fiel…
XMM-Newton observations of the interacting galaxy pairs NGC 7771/0 and NGC 2342/1
Zezas, A.; Roberts, T. P.; Ward, M. J. +1 more
We present XMM-Newton X-ray observations of the interacting galaxy pairs NGC 7771/7770 and NGC 2342/2341. In NGC 7771, for the first time we are able to resolve the X-ray emission into a bright central source plus two bright (LX > 1040 erg s-1) ultraluminous X-ray sources (ULXs) located either end of the bar. In…
High-resolution extreme ultraviolet spectroscopy of G191-B2B: structure of the stellar photosphere and the surrounding interstellar medium
Dreizler, S.; Barstow, M. A.; Hubeny, I. +8 more
We have continued our detailed analysis of the high-resolution (R= 4000) spectroscopic observation of the DA white dwarf G191-B2B, obtained by the Joint Astrophysical Plasmadynamic Experiment (J-PEX) normal incidence sounding rocket-borne telescope, comparing the observed data with theoretical predictions for both homogeneous and stratified atmosp…
On the X-ray properties of OH megamaser sources: Chandra snapshot observations
Brandt, William N.; Comastri, Andrea; Vignali, Cristian +1 more
We present Chandra snapshot observations for a sample of seven sources selected from the Arecibo OH megamaser (OHM) survey at z~ 0.13-0.22 and with far-infrared (FIR) luminosities in excess of 1011Lsolar. In contrast with the known H2O megamasers, which are mostly associated with powerful active galactic nuclei (AG…
ISO observations of 3-200 µm emission by three dust populations in an isolated local translucent cloud
Juvela, M.; Lemke, D.; Lehtinen, K. +2 more
We present ISOPHOT spectrophotometry of three positions within the isolated high-latitude cirrus cloud G 300.2-16.8, spanning from the near- to far-infrared (NIR to FIR). The positions exhibit contrasting emission spectrum contributions from the unidentified infrared bands (UIBs), very small grains (VSGs) and large classical grains, and both semi-…