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Wolf-Rayet stars in M33 - II. Optical spectroscopy of emission-line stars in giant HII regions
Drissen, Laurent; Úbeda, Leonardo; Crowther, Paul A. +1 more
We present optical spectra of 14 emission-line stars in M33's giant HII regions NGC 592,595 and 604: five of them are known Wolf-Rayet (WR) stars, for which we present a better quality spectrogram, eight are WR candidates based on narrow-band imagery and one is a serendipitous discovery. Spectroscopy confirms the power of interference filter image…
Luminosity-colour relations for thin-disc main-sequence stars
Cabrera-Lavers, A.; Bilir, S.; Yaz, E. +3 more
In this study we present the absolute magnitude calibrations of thin-disc main-sequence stars in the optical , and in the near-infrared . Thin-disc stars are identified by means of Padova isochrones, and absolute magnitudes for the sample are evaluated via the newly reduced Hipparcos data. The obtained calibrations cover a large range of spectral …
Exploring the disc/jet interaction in the radio-loud quasar 4C+74.26 with Suzaku
Larsson, J.; Fabian, A. C.; Miniutti, G. +1 more
We report on a 90 ks Suzaku observation of the radio-loud quasar 4C+74.26. The source was observed in its highest flux state to date, and we find that it brightened by about 20 per cent during the observation. We see evidence of spectral hardening as the count rate increases and also find that the rms variability increases with energy up to about …
Evolution in the discs and bulges of group galaxies since z = 0.4
Mulchaey, John S.; Balogh, Michael L.; Oemler, Augustus, Jr. +4 more
We present quantitative morphology measurements of a sample of optically selected group galaxies at 0.3 < z < 0.55 using the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) and the GIM2D surface brightness fitting software package. The group sample is derived from the Canadian Network for Observational Cosmology Field Galaxy R…
Origin of X-ray emission from transient black hole candidates in quiescence
Yuan, Feng; Zhang, Hui; Cui, Wei +1 more
We report results from a systematic study of X-ray emission from black hole transients in quiescence. In this state, mass accretion is thought to follow the geometry of an outer optically thick, geometrically thin disc and an inner optically thin, geometrically thick radiatively inefficient accretion flow (RIAF). The inner flow is likely also coup…
GD 552: a cataclysmic variable with a brown dwarf companion?
Gänsicke, B. T.; Dhillon, V. S.; Marsh, T. R. +7 more
GD 552 is a high proper motion star with the strong, double-peaked emission lines characteristic of the dwarf nova class of cataclysmic variable (CV) star, and yet no outburst has been detected during the past 12yr of monitoring. We present spectroscopy taken with the aim of detecting emission from the mass donor in this system. We fail to do so a…
Reflection-dominated X-ray spectra of narrow-line Seyfert 1 galaxies: Mrk 478 and EXO 1346.2+2645
Fabian, A. C.; Gallo, L. C.; Zoghbi, A.
Multi-epoch XMM-Newton spectra of the two narrow-line Seyfert 1 (NLS1), Mrk 478 and EXO 1346.2+2645, are presented. The data were fitted with different models, including the relativistically blurred reflection model REFLIONX, which was found to give a good description of both spectra in all epochs. The two sources are reflection dominated with the…
PKS2250-41: a case study for triggering
Villar-Martín, M.; Morganti, R.; Tadhunter, C. N. +3 more
We present the results of a multiwavelength study of the z = 0.31 radio source PKS2250-41. Integral field unit and long-slit spectroscopy obtained using VIMOS and FORS1 on the VLT, and archival Hubble Space Telescope optical imaging observations are used to study the morphology, kinematics and ionization state of the extended emission-line region …
Peering through the stellar wind of IGR J19140+0951 with simultaneous INTEGRAL/RXTE observations
Rodriguez, J.; Shaw, S. E.; Hannikainen, D. C. +1 more
We have used the RXTE and INTEGRAL satellites simultaneously to observe the high-mass X-ray binary (HMXB) IGR J19140+0951. The spectra obtained in the 3-80 keV range have allowed us to perform a precise spectral analysis of the system along its binary orbit. The spectral evolution confirms the supergiant nature of the companion star and the neutro…
High-resolution polarimetry of Parsamian 21: revealing the structure of an edge-on FUOri disc
Apai, D.; Ábrahám, P.; Kóspál, Á. +6 more
We present the first high spatial resolution near-infrared direct and polarimetric observations of Parsamian 21, obtained with the Nasmyth Adaptive Optics System-CONICA instrument at the Very Large Telescope (VLT). We complemented these measurements with archival infrared observations, such as Hubble Space Telescope (HST)/Wide Field Planetary Came…