Search Publications
Spectral response of the pulsationally induced shocks in the atmosphere of BW Vulpeculae
Smith, Myron A.; Jeffery, C. Simon
BW Vulpeculae (BW Vul) is remarkable for exciting an extremely strong radial pulsation mode which grows through its outer envelope and forms visible shock features in the atmosphere. Material propelled upwards by the shock returns violently to the lower photosphere where it creates a second shock just before the start of the next cycle. We have ob…
HST/WFPC2 snapshot imaging of symbiotic stars
Eyres, S. P. S.; Bode, M. F.; Brocksopp, C.
The results of a HST/WFPC2 snapshot imaging survey of selected symbiotic stars in 1999/2000 are presented. Seven sources - HD 149427 (PC 11), PU Vul, RT Ser, He2-104 (Southern Crab), V1329 Cyg (HBV 475), V417 Cen and AS 201 - were observed in filters F218W (ultraviolet continuum), F502N ([O III]λλ 4959, 5007) and F656N (Hαλ 6563); an eighth source…
XMM-Newton observations of an absorbed z= 0.67 QSO: no dusty torus?
Georgakakis, A.; Georgantopoulos, I.; Griffiths, R. E. +4 more
We present XMM-Newton observations of AX J0341.4-4453, a mildly reddened AV < 7 quasi-stellar object (QSO) at a redshift of z= 0.672. The XMM-Newton spectrum shows a large obscuring column NH~ 1023 cm-2 corresponding to AV~ 70, in agreement with previous results based on the lower limit of …
A search for X-ray variability in the open cluster NGC 2516
Ramsay, Gavin; Harra, Louise; Kay, Hilary
We present the results of a search for X-ray variability in the Galactic open cluster NGC 2516. This cluster has been observed on eight occasions using XMM-Newton, making it an excellent target for such a study. We find four sources that show significant variability, implying the detection of one significantly variable source every 25 ks. All sour…
A study of velocity fields in the transition region of ɛ Eri (K2 V)
Jordan, C.; Sim, S. A.
Analyses of the widths and shifts of optically thin emission lines in the ultraviolet spectrum of the active dwarf ɛ Eri (K2 V) are presented. The spectra were obtained using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. The linewidths are used to find the non-thermal energy …
The optical jet in 3C 31 on 15 arcsec scales
Croston, J. H.; Birkinshaw, M.; Davies, R. L. +1 more
Evidence has been found for optical emission from the northern radio jet of 3C 31, the radio source associated with NGC 383. The jet emerges from the dust disc and ring of emission at a radius of 5 arcsec, and within 10.4 arcsec is measured to have a B-band flux of 2.1 µJy and an R-band flux of 2.3 µJy. The radio-to-optical spectral in…
The obscured QSO 1SAX J1218.9+2958
Page, M. J.; Ramsay, G.; Loaring, N. S.
We present results from XMM-Newton observations of the obscured quasi-stellar object 1SAX J1218.9+2958. We find that the previously reported optical and soft X-ray counterpart positions are incorrect. However, we confirm the spectroscopic redshift of 0.176. The optical counterpart has a K magnitude of 13.5 and an R-K colour of 5.0 and is therefore…
The brightness temperature problem in extreme intra-day variable quasars: a model for PKS 0405-385
Protheroe, R. J.
I re-examine the brightness temperature problem in PKS 0405-385, which is an extreme intra-day variable radio quasar with an inferred brightness temperature of ~5 × 1014 K at 5 GHz, well above the Compton catastrophe limit of ~1011 K that is reached when the synchrotron photon energy density exceeds the energy density of the …
Implementing TOPbase/Iron Project: continuous absorption from FeII
Bautista, Manuel; Cowley, Charles R.
We discuss implementation of TOPbase and Iron Project opacities for stellar spectral codes. We use a technique employed by Peach, where a Boltzmann-averaged cross-section is calculated for selected temperatures, and the opacity obtained from double interpolation in temperature and wavelength. It is straightforward to include all levels for which c…
Spectroscopic diagnostics of UV power and accretion in T Tauri stars
Brooks, D. H.; Costa, V. M.
It is known that in the upper atmospheres of the Sun and some late-type stars there is a systematic relationship between the optically thin total radiated power and the power emitted by single spectral lines. Using recently derived emission-measure distributions from IUE spectra for BP Tau, CV Cha, RY Tau, RU Lupi and GW Ori, we demonstrate that t…