Search Publications
Accretion, jets and winds: High-energy emission from young stellar objects
Günther, H. M.
This article summarizes the processes of high-energy emission in young stellar objects. Stars of spectral type A and B are called Herbig Ae/Be (HAeBe) stars in this stage, all later spectral types are termed classical T Tauri stars (CTTS). Both types are studied by high-resolution X-ray and UV spectroscopy and modeling. Three mechanisms contribute…
Water in star-forming regions with Herschel
van Dishoeck, E. F.; Kristensen, L. E.
The Herschel Space Observatory is well suited to address several important questions in star- and planet formation, as is evident from its first year of operation. This paper focuses on observations of water, a key molecule in the physics and chemistry of star-formation. In the WISH Key Program, a comprehensive set of water lines is being obtained…
A 2007 photometric study and UV spectral analysis of the Wolf-Rayet binary V444 Cyg
Ekmekçi, F.; Eriş, F. Z.
Photometric and spectroscopic characteristics of the WN5+O6 binary system, V444 Cyg, were studied. The Wilson-Devinney (WD) analysis, using new BV observations carried out at the Ankara University Observatory, revealed the masses, radii, and temperatures of the components of the system as MWR=10.64 M⊙, MO=24.68 M
Six years of XMM-Newton observations of NGC 1313 X-1 and X-2
Pintore, F.; Zampieri, L.
We present a systematic analysis of the X-ray spectra of NGC 1313 X-1 and NGC 1313 X-2, using six years of XMM-Newton observations (17 observations). We fitted the continuum with a Comptonization model plus a multicolor blackbody disc, that describes the effects of an accretion disc plus an optically thick corona. We checked the consistency of thi…
Optical variability of the ultraluminous X-ray source NGC 1313 X-2
Falomo, R.; Soria, R.; Zampieri, L. +2 more
We analyzed the longest phase-connected photometric dataset available for NGC 1313 X-2, looking for the ∼6 day modulation reported by Liu et al. (2009). The folded B-band light curve shows a 6 days periodicity with a significance slightly larger than 3σ. The low statistical significance of this modulation, along with the lack of detection in the V…
Key results from an XMM-Newton and Chandra study of a new sample of extreme ULXs from the 2XMM catalogue
Roberts, T. P.; Walton, D. J.; Sutton, A. D.
We present highlights from a study of a sample of 10 extreme-luminosity candidate ultraluminous X-ray sources (L_X>5 × 1040 erg s-1), all at distances <100 Mpc, identified from a cross-correlation of the RC3 catalogue of galaxies with the 2XMM catalogue. Five of the sample have also been observed by Chandra. Of the 10 s…
A large catalogue of ultraluminous X-ray source candidates in nearby galaxies
Roberts, T. P.; Walton, D. J.; Gladstone, J. C. +1 more
Since their discovery, Ultraluminous X-ray sources (ULXs) have attracted attention due to their combination of extreme luminosities and extra-nuclear locations. However, they are a fairly rare phenomenon, and attempts to investigate the general properties of the population have been hindered by a relative lack of known sources. Here, we present a …
Does NGC 5408 X-1 really contain an intermediate-mass black hole?
Done, C.; Roberts, T. P.; Middleton, M. J. +1 more
NGC 5408 X-1 is one of only a handful of ultraluminous X-ray sources (ULXs) to demonstrate a strong quasi-periodic oscillation (QPO) in its lightcurve. This has been interpreted as being analogous to the type C low-frequency QPO seen in black hole binaries (BHBs) when accreting at sub-Eddington rates, implying an intermediate-mass black hole (IMBH…
Rest-frame UV to optical X-shooter spectrum of the gravitationally lensed galaxy ``the 8 o'clock arc'': Dissection of its physical properties
Schaerer, D.; Dessauges-Zavadsky, M.; Richard, J. +2 more
We present the rest-frame UV to optical spectrum of the gravitationally lensed galaxy, the ``8 o'clock arc'' at z=2.735, obtained with the X-shooter spectrograph. This is one of the rare comprehensive study of a high-redshift star-forming galaxy, usually not feasible due to the faintness of these objects. The spectrum of the 8 o'clock arc is rich …
Masses and luminosities of O- and B-type stars and red supergiants
Neuhäuser, R.; Hohle, M. M.; Schutz, B. F.
Massive stars are of interest as progenitors of supernovae, i.e. neutron stars and black holes, which can be sources of gravitational waves. Recent population synthesis models can predict neutron star and gravitational wave observations but deal with a fixed supernova rate or an assumed initial mass function for the population of massive stars. He…