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On the production of He, C, and N by low- and intermediate-mass stars: a comparison of observed and model-predicted planetary nebula abundances
Balick, B.; Henry, R. B. C.; Stephenson, B. G. +2 more
The primary goal of this paper is to make a direct comparison between the measured and model-predicted abundances of He, C, and N in a sample of 35 well-observed Galactic planetary nebulae (PNe). All observations, data reductions, and abundance determinations were performed in house to ensure maximum homogeneity. Progenitor star masses (M ≤ 4 M
Absorption and emission features of 7Be II in the outburst spectra of V838 Her (Nova Her 1991)
Molaro, P.; Izzo, L.; Selvelli, P.
High- and low-resolution International Ultraviolet Explorer (IUE) spectra of V838 Her in the early outburst stages exhibit a strong absorption feature shortward of λ3130. We discuss the nature of this spectral feature and provide convincing evidence that it corresponds to the blueshifted resonance doublet of singly ionized 7Be recently …
Ultraviolet stellar population of the old open cluster M67 (NGC 2682)
Subramaniam, Annapurni; Sindhu, N.; Radha, C. Anu
We present the results of ultraviolet (UV) photometry of the old open cluster M67 obtained using Galaxy Evolution Explorer in far-ultraviolet (FUV) and near-ultraviolet (NUV) bands. UV detections of 18 blue straggler stars (BSSs), 3 white dwarfs (WDs), 4 yellow straggler stars, 2 sub-subgiants, and 25 X-ray sources are presented (along with an onl…
A new look inside planetary nebula LoTr 5: a long-period binary with hints of a possible third component
Montesinos, B.; Lillo-Box, J.; Zorotovic, M. +5 more
LoTr 5 is a planetary nebula with an unusual long-period binary central star. As far as we know, the pair consists of a rapidly rotating G-type star and a hot star, which is responsible for the ionization of the nebula. The rotation period of the G-type star is 5.95 d and the orbital period of the binary is now known to be ∼2700 d, one of the long…
Polarization light curve modelling of corotating interaction regions in the wind of the Wolf-Rayet star WR 6
Ignace, Richard; St-Louis, N.; Tremblay, Patrick
The intriguing WN4b star WR 6 has been known to display epoch-dependent spectroscopic, photometric and polarimetric variability for several decades. In this paper, we set out to verify if a simplified analytical model in which corotating interaction regions (CIRs) threading an otherwise spherical wind is able to reproduce the many broad-band conti…
Broad absorption line symbiotic stars: highly ionized species in the fast outflow from MWC 560
Sokoloski, J. L.; Knigge, Christian; Lucy, Adrian B.
In symbiotic binaries, jets and disc winds may be integral to the physics of accretion on to white dwarfs from cool giants. The persistent outflow from symbiotic star MWC 560 (≡V694 Mon) is known to manifest as broad absorption lines (BALs), most prominently at the Balmer transitions. We report the detection of high-ionization BALs from C IV, Si I…
Surface abundance and the hunt for stratification in chemically peculiar hot subdwarfs: PG 0909+276 and UVO 0512-08
Wild, J. F.; Jeffery, C. S.
Edelmann identified two chemically peculiar hot subdwarfs, PG 0909+276 and UVO 0512-08, as having very high overabundances of iron-group elements. We obtained high-resolution ultraviolet spectroscopy in order to measure abundances of species not observable in the optical, and to seek evidence for chemical stratification in the photosphere. Abundan…
An ultraviolet study of B[e] stars: evidence for pulsations, luminous blue variable type variations and processes in envelopes
Krtička, J.; Krtičková, I.
Stars that exhibit a B[e] phenomenon comprise a very diverse group of objects in a different evolutionary status. These objects show common spectral characteristics, including the presence of Balmer lines in emission, forbidden lines and strong infrared excess due to dust. Observations of emission lines indicate illumination by an ultraviolet ioni…
Spectral energy distribution variations of nearby Seyfert galaxies during AGN watch monitoring programs
Vestergaard, M.; Kilerci Eser, Ece
We present and analyse quasi-simultaneous multi-epoch spectral energy distributions (SEDs) of seven reverberation-mapped active galactic nuclei (AGNs) for which accurate black hole mass measurements and suitable archival data are available from the `AGN Watch' monitoring programs. We explore the potential of optical-UV and X-ray data, obtained wit…
Modelling the diffuse dust emission around Orion
Shalima, P.; Gogoi, Rupjyoti; Saikia, Gautam
We have studied the diffuse radiation in the surroundings of M42 using photometric data from the Galaxy Evolution Explorer (GALEX) in the far-ultraviolet (FUV) and infrared observations of the AKARI space telescope. The main source of the FUV diffuse emission is the starlight from the Trapezium stars scattered by dust in front of the nebula. We in…