Search Publications
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…
Some statistical aspects of estimating the local red clump absolute magnitude
Koen, Chris; Lombard, Fred
Various statistical issues regarding estimation of the mean absolute magnitude of the red clump stars, using Hipparcos parallaxes, are discussed. The problem is put in the broader context of estimation of the functional dependence of the absolute magnitude on colour of local giant stars, as derived from Hipparcos observations. The methods used inc…
On the origin of the X-ray emission from a narrow-line radio quasar at z > 1
Barcons, X.; Carballo, R.; Warwick, R. S. +5 more
We present new XMM-Newton X-ray observations of the z= 1.246 narrow-line radio quasar RX J1011.2+5545 serendipitously discovered by ROSAT. The flat X-ray spectrum previously measured by ROSAT and ASCA is shown to be the result of a steep Γ~ 1.8 power-law spectrum seen through a moderate intrinsic absorbing column (NH~ 4 × 1021
On the importance of searching for oscillations of the Jovian inner radiation belt with a quasi-period of 40 minutes
Lou, Yu-Qing; Zheng, Chen
Experiments aboard the Ulysses spacecraft discovered quasi-periodic bursts of relativistic electrons and of radio emissions with ~40-min period (QP-40) from the south polar direction of Jupiter in 1992 February. Such polar QP-40 burst activities were found to correlate well with arrivals of high-speed solar winds at Jupiter. We advance the physica…