TY  - JOUR
A1  - Richardson, Noel D.
A1  - Russell, Christopher M. P.
A1  - St-Jean, Lucas
A1  - Moffat, Anthony F. J.
A1  - St-Louis, Nicole
A1  - Shenar, Tomer
A1  - Pablo, Herbert
A1  - Hill, Grant M.
A1  - Ramiaramanantsoa, Tahina
A1  - Corcoran, Michael
A1  - Hamuguchi, Kenji
A1  - Eversberg, Thomas
A1  - Miszalski, Brent
A1  - Chene, Andre-Nicolas
A1  - Waldron, Wayne
A1  - Kotze, Enrico J.
A1  - Kotze, Marissa M.
A1  - Luckas, Paul
A1  - Cacella, Paulo
A1  - Heathcote, Bernard
A1  - Powles, Jonathan
A1  - Bohlsen, Terry
A1  - Locke, Malcolm
A1  - Handler, Gerald
A1  - Kuschnig, Rainer
A1  - Pigulski, Andrzej
A1  - Popowicz, Adam
A1  - Wade, Gregg A.
A1  - Weiss, Werner W.
T1  - The variability of the BRITE-est Wolf-Rayet binary, gamma(2) Velorum-I. Photometric and spectroscopic evidence for colliding winds
JF  - Monthly notices of the Royal Astronomical Society
N2  - We report on the first multi-colour precision light curve of the bright Wolf-Rayet binary gamma(2) Velorum, obtained over six months with the nanosatellites in the BRITE-Constellation fleet. In parallel, we obtained 488 high-resolution optical spectra of the system. In this first report on the data sets, we revise the spectroscopic orbit and report on the bulk properties of the colliding winds. We find a dependence of both the light curve and excess emission properties that scales with the inverse of the binary separation. When analysing the spectroscopic properties in combination with the photometry, we find that the phase dependence is caused only by excess emission in the lines, and not from a changing continuum. We also detect a narrow, high-velocity absorption component from the He perpendicular to lambda 5876 transition, which appears twice in the orbit. We calculate smoothed-particle hydrodynamical simulations of the colliding winds and can accurately associate the absorption from He perpendicular to to the leading and trailing arms of the wind shock cone passing tangentially through our line of sight. The simulations also explain the general strength and kinematics of the emission excess observed in wind lines such as C III lambda 5696 of the system. These results represent the first in a series of investigations into the winds and properties of gamma(2) Velorum through multi-technique and multi-wavelength observational campaigns.
KW  - stars: early type
KW  - stars: individual: gamma(2) Vel
KW  - stars: mass loss
KW  - stars: winds
KW  - outflows
KW  - stars: Wolf-Rayet
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx1731
SN  - 0035-8711
SN  - 1365-2966
VL  - 471
SP  - 2715
EP  - 2729
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Gvaramadze, V. V.
A1  - Kniazev, A. Y.
A1  - Miroshnichenko, A. S.
A1  - Berdnikov, Leonid N.
A1  - Langer, N.
A1  - Stringfellow, G. S.
A1  - Todt, Helge Tobias
A1  - Hamann, Wolf-Rainer
A1  - Grebel, E. K.
A1  - Buckley, D.
A1  - Crause, L.
A1  - Crawford, S.
A1  - Gulbis, A.
A1  - Hettlage, C.
A1  - Hooper, E.
A1  - Husser, T. -O.
A1  - Kotze, P.
A1  - Loaring, N.
A1  - Nordsieck, K. H.
A1  - O'Donoghue, D.
A1  - Pickering, T.
A1  - Potter, S.
A1  - Colmenero, E. Romero
A1  - Vaisanen, P.
A1  - Williams, T.
A1  - Wolf, M.
A1  - Reichart, D. E.
A1  - Ivarsen, K. M.
A1  - Haislip, J. B.
A1  - Nysewander, M. C.
A1  - LaCluyze, A. P.
T1  - Discovery of two new Galactic candidate luminous blue variables with Wide-field Infrared Survey Explorer
JF  - Monthly notices of the Royal Astronomical Society
N2  - We report the discovery of two new Galactic candidate luminous blue variable (LBV) stars via detection of circular shells (typical of confirmed and candidate LBVs) and follow-up spectroscopy of their central stars. The shells were detected at 22 mu m in the archival data of the Mid-Infrared All Sky Survey carried out with the Wide-field Infrared Survey Explorer (WISE). Follow-up optical spectroscopy of the central stars of the shells conducted with the renewed Southern African Large Telescope (SALT) showed that their spectra are very similar to those of the well-known LBVs P Cygni and AG Car, and the recently discovered candidate LBV MN112, which implies the LBV classification for these stars as well. The LBV classification of both stars is supported by detection of their significant photometric variability: one of them brightened in the R and I bands by 0.68 +/- 0.10 and 0.61 +/- 0.04 mag, respectively, during the last 1318 years, while the second one (known as Hen 3-1383) varies its B, V, R, I and Ks brightnesses by similar or equal to 0.50.9 mag on time-scales from 10 d to decades. We also found significant changes in the spectrum of Hen 3-1383 on a time-scale of similar or equal to 3 months, which provides additional support for the LBV classification of this star. Further spectrophotometric monitoring of both stars is required to firmly prove their LBV status. We discuss a connection between the location of massive stars in the field and their fast rotation, and suggest that the LBV activity of the newly discovered candidate LBVs might be directly related to their possible runaway status.
KW  - line: identification
KW  - circumstellar matter
KW  - stars: emission-line, Be
KW  - stars: evolution
KW  - stars: individual: Hen 3-1383
KW  - stars: massive
Y1  - 2012
U6  - https://doi.org/10.1111/j.1365-2966.2012.20556.x
SN  - 0035-8711
VL  - 421
IS  - 4
SP  - 3325
EP  - 3337
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Todt, Helge Tobias
A1  - Kniazev, A. Y.
A1  - Gvaramadze, V. V.
A1  - Hamann, Wolf-Rainer
A1  - Buckley, D.
A1  - Crause, L.
A1  - Crawford, S. M.
A1  - Gulbis, A. A. S.
A1  - Hettlage, C.
A1  - Hooper, E.
A1  - Husser, T. -O.
A1  - Kotze, P.
A1  - Loaring, N.
A1  - Nordsieck, K. H.
A1  - O'Donoghue, D.
A1  - Pickering, T.
A1  - Potter, S.
A1  - Romero-Colmenero, E.
A1  - Vaisanen, P.
A1  - Williams, T.
A1  - Wolf, M.
T1  - Abell 48-a rare WN-type central star of a planetary nebula
JF  - Monthly notices of the Royal Astronomical Society
N2  - A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. Almost all of these H-deficient central stars (CSs) display spectra with strong carbon and helium lines. Most of them exhibit emission-line spectra resembling those of massive WC stars. Therefore these stars are classed as CSPNe of spectral type [WC]. Recently, quantitative spectral analysis of two emission-line CSs, PB 8 and IC 4663, revealed that these stars do not belong to the [WC] class. Instead PB 8 has been classified as [WN/WC] type and IC 4663 as [WN] type. In this work we report the spectroscopic identification of another rare [WN] star, the CS of Abell 48. We performed a spectral analysis of Abell 48 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. We find that the expanding atmosphere of Abell 48 is mainly composed of helium (85 per cent by mass), hydrogen (10 per cent) and nitrogen (5 per cent). The residual hydrogen and the enhanced nitrogen abundance make this object different from the other [WN] star IC 4663. We discuss the possible origin of this atmospheric composition.
KW  - stars: abundances
KW  - stars: AGB and post-AGB
KW  - stars: mass-loss
KW  - stars: Wolf-Rayet
KW  - planetary nebulae: general
KW  - planetary nebulae: individual: PN G029.0+00.4
Y1  - 2013
U6  - https://doi.org/10.1093/mnras/stt056
SN  - 0035-8711
SN  - 1365-2966
VL  - 430
IS  - 3
SP  - 2302
EP  - 2312
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Grobler, J. P.
A1  - Hartl, G. B.
A1  - Grobler, N.
A1  - Kotze, A.
A1  - Botha, K.
A1  - Tiedemann, Ralph
T1  - The genetic status of an isolated black wildebeest (Connochaetes gnou) population from the Abe Bailey Nature Reserve, South Africa : Microsatellite data on a putative past hybridization with blue wildebeest (C-taurinus)
N2  - The present study aimed at assessing genetic purity of black wildebeest (Connochoetes gnou) at Abe Bailey Nature Reserve, Gauteng Province, South Africa, using a multitocus microsatellite approach. Five loci were studied in black and blue (C. taurinus) wildebeest, the latter being a closely related species and known to produce hybrids with the morphologically very similar black wildebeest. In fact, the entire national black wildebeest population of South Africa potentially contains a significant proportion of introgressed blue wildebeest genes. In our case, eight out of 39 alleles were unique to black and 22 to blue wildebeest, with nine alleles shared between pure populations of the two species in Line with their taxonomic proximity. A possible Limited past introgression of blue wildebeest genes into the Abe Bailey population, corresponding to documents on population history, was only supported by the presence of a single allele otherwise exclusively found in samples of four pure blue but not in samples of two pure black wildebeest control populations. However, an assignment test and coefficients of population divergence did not support an extended introgression of C. taurinus alleles into the C. gnou population under study. Average heterozygosity at Abe Bailey proved to be intermediate between black and blue wildebeest, the tatter species generally harbouring more genetic variation than the former owing to larger population sizes and the absence of population bottlenecks in historical times. The implications of our data are discussed with reference to the persistence of introgressed genes and the conservation of pure black wildebeest gene pools
Y1  - 2005
SN  - 1616-5047
ER  -