Search Publications
A high-resolution ultraviolet absorption spectrum of supernova ejecta in SN1006
Blair, William P.; Fesen, Robert A.; Hamilton, Andrew J. S.
We report a high-resolution, far-ultraviolet, Space Telescope Imaging Spectrograph (STIS) E140M spectrum of the strong, broad SiII, III and IV features produced by the ejecta of the supernova of 1006 AD (SN1006) seen in absorption against the background Schweizer-Middleditch OB subdwarf star. The spectrum confirms the extreme sharpness of the red …
New flaring of an ultraluminous X-ray source in NGC1365
Zezas, A.; La Parola, V.; Baldi, A. +4 more
We have studied a highly variable ultraluminous X-ray source (ULX) in the Fornax galaxy NGC1365, with a series of 12 Chandra and XMM-Newton observations between 2002 and 2006. In 2006 April, the source peaked at a luminosity ~3 × 1040erg s-1 in the 0.3-10 keV band (similar to the maximum luminosity found by ASCA in 1995), and…
Wind-wind collision in the η Carinae binary system - III. The HeII λ4686 line profile
Falceta-Gonçalves, D.; Abraham, Z.
We modelled the HeII λ4686 line profiles observed in the η Carinae binary system close to the 2003.5 spectroscopic event, assuming that they were formed in the shocked gas that flows at both sides of the contact surface formed by wind-wind collision. We used a constant flow velocity and added turbulence in the form of a Gaussian velocity distribut…
Semiregular variables in the solar neighbourhood
Glass, I. S.; van Leeuwen, F.
Period-luminosity sequences have been shown to exist among the semiregular variables (SRVs) in the Magellanic Clouds, the bulge of the Milky Way galaxy and elsewhere. Using modern-period and revised Hipparcos parallax data, this paper demonstrates that they also appear among the M giant SRVs of the solar neighbourhood. Their distribution in the K,…
The stellar halo of the edge-on galaxy NGC 891
Rejkuba, M.; Mouhcine, M.; Ibata, R.
Using the Advanced Camera for Surveys on board the Hubble Space Telescope, we have resolved individual red giant branch stars in the outskirts of the edge-on galaxy NGC 891, down to ~2 mag fainter than the tip of the red giant branch. The data set allows investigation of the stellar populations in the outer regions of an analogue galaxy to the Mil…
Timing evidence in determining the accretion state of the Seyfert galaxy NGC 3783
Uttley, P.; Arévalo, P.; McHardy, I. M. +2 more
Previous observations with the Rossi X-ray Timing Explorer (RXTE) have suggested that the power spectral density (PSD) of NGC 3783 flattens to a slope near zero at low frequencies, in a similar manner to that of Galactic black hole X-ray binary systems (GBHs) in the `hard' state. The low radio flux emitted by this object, however, is inconsistent …
0.5 Mpc-scale extended X-ray emission in the z = 2.48 radio galaxy 4C 23.56
Dunlop, J.; Almaini, O.; Best, P. N. +1 more
We present an XMM-Newton observation of the radio galaxy 4C 23.56 at z = 2.48 which reveals extended X-ray emission coincident with the radio lobes spanning ~0.5 Mpc. These are the largest X-ray-bright lobes known at z > 2. Under the assumption that these features result from inverse-Compton scattering of cosmic microwave background photons by …
Needles in haystacks: how to use contemporaneous data in the search for low-frequency modes of oscillation of the Sun
Chaplin, W. J.; Elsworth, Y.; Appourchaux, T. +1 more
We show how to take advantage of contemporaneous data from two different instruments in the search for low-frequency modes of oscillation of the Sun. Contemporaneous data allow searches to be made for prominent, sharp concentrations of power which are coincident in frequency. Crucial to determining objective measures of the joint probability of th…
The long-term evolution and initial size of comets 46P/Wirtanen and 67P/Churyumov-Gerasimenko
Lamy, P. L.; Groussin, O.; Hahn, G. +2 more
We present a new method to study the long-term evolution of cometary nuclei in order to estimate their original size, and we consider the case of comets 46P/Wirtanen (hereafter 46P) and 67P/Churyumov-Gerasimenko (hereafter 67P). We calculate the past evolution of the orbital elements of both comets over 100000yr using a Bulirsch-Stoer integrator a…
The effect of dust on Tremaine-Weinberg measurements
Gerssen, Joris; Debattista, Victor P.
We investigate the effect of dust on the observed rotation rate of a stellar bar. The only direct way to measure this quantity relies on the Tremaine & Weinberg (TW) method which requires that the tracer satisfies the continuity equation. Thus, it has been applied largely to early-type barred galaxies. We show using numerical simulations of ba…