9C: a survey of radio sources at 15 GHz with the Ryle Telescope   总被引：1，自引：0，他引：1  

Elizabeth M. Waldram  Guy G. Pooley  Keith J. B. Grainge  Michael E. Jones  Richard D. E. Saunders  Paul F. Scott  Angela C. Taylor 《Monthly notices of the Royal Astronomical Society》2003,342(3):915-925

The fields chosen for the first observations of the cosmic microwave background with the Very Small Array have been surveyed with the Ryle Telescope at 15 GHz. We have covered three regions around RA  00^h 20^m Dec. +30°  , RA  09^h 40^m Dec. +32°  and RA  15^h 40^m Dec. +43° (J2000.0)  , an area of  520 deg²  . There are 465 sources above the current completeness limit of  ≈25 mJy  , although a total of  ≈760  sources have been detected, some as faint as 10 mJy. This paper describes our techniques for observation and data analysis; it also includes source counts and some discussion of spectra and variability. Preliminary source lists are presented.  相似文献   

A measurement of H₀ from Ryle Telescope, ASCA and ROSAT observations of Abell 773     

Richard Saunders  Rüdiger Kneissl  Keith Grainge  William F. Grainger  Michael E. Jones  Alessia Maggi  Rhiju Das  †  Alastair C. Edge  Anthony N. Lasenby  G. G. Pooley  Shigeru J. Miyoshi  Taisuke Tsuruta  Koujun Yamashita  Yuzuru Tawara  Akihiro Furuzawa  Akihiro Harada  Izamu Hatsukade 《Monthly notices of the Royal Astronomical Society》2003,341(3):937-940

  相似文献   

A maximum-likelihood approach to removing radio sources from observations of the Sunyaev–Zel'dovich effect, with application to Abell 611     

William F. Grainger  Rhiju Das†  Keith Grainge  Michael E. Jones  Rüdiger Kneissl  G. G. Pooley  Richard D. E. Saunders 《Monthly notices of the Royal Astronomical Society》2002,337(4):1207-1214

  相似文献   

Variable circular polarization associated with relativistic ejections from GRS 1915 + 105     

R. P. Fender  D. Rayner  D. G. McCormick  T. W. B. Muxlow  G. G. Pooley  R. J. Sault  R. E. Spencer 《Monthly notices of the Royal Astronomical Society》2002,336(1):39-46

We describe H α , SCUBA and MERLIN imaging of the interacting galaxy pair NGC 4490 and 4485. We detect an H α filament emerging from the disc of NGC 4490 to a projected distance of 3 kpc which has counterparts in both the radio continuum and H  i . The H  i counterpart extends to a projected distance of ∼30 kpc from NGC 4490 and we argue that this is evidence that the giant H  i envelope in this system has its origins in star formation. We use SCUBA and radio continuum data to attempt to place constraints on the distribution of dust with respect to the star forming regions. This analysis is limited by the lack of an independent estimate of the dust temperature, something that both 'SIRTF' and 'SOFIA' will be able to provide, however we find some evidence that most obscuring dust is not located within H  ii regions themselves.  相似文献   

A search for periodicities in the radio emission from XTE J1118+480     

G.G. Pooley 《Monthly notices of the Royal Astronomical Society》2001,324(1):L23-L24

A search for modulation of the 15-GHz radio flux density at the orbital period from the X-ray nova XTE J1118+480 during its outburst in 2000 April–June found no signal ≳ a few per cent of the mean. No orbital modulation was found in the RXTE ASM data over the same interval.  相似文献   

Spectral, polarization and time-lag properties of GRS 1915+105 radio oscillations     

R.P.Fender  D.Rayner  S.A.Trushkin  K.O'Brien  R.J.Sault  G.G.Pooley  R.P.Norris 《Monthly notices of the Royal Astronomical Society》2002,330(1):212-218

We report high-sensitivity dual-frequency observations of radio oscillations from GRS 1915+105 following the decay of a major flare event in 2000 July. The oscillations are clearly observed at both frequencies, and the time-resolved spectral index traces the events between optically thin and thick states. While previously anticipated from sparse observations and simple theory, this is the first time a quasi-periodic signal has been seen in the radio spectrum, and is a clear demonstration that flat radio spectra can arise from the combination of emission from optically thick and thin regions. In addition, we measure the linear polarization of the oscillations, at both frequencies, at a level of about  1–2  per cent, with a flat spectrum. Cross-correlating the two light curves we find a mean delay, in the sense that the emission at 8640 MHz leads that at 4800 MHz, of around 600 s. Comparison with frequency-dependent time-delays reported in the literature reveals that this delay is variable between epochs. We briefly discuss possible origins for a varying time-delay, and suggest possible consequences.  相似文献   

How rapidly do neutron stars spin at birth? Constraints from archival X-ray observations of extragalactic supernovae     

Rosalba Perna  Roberto Soria  Dave Pooley  Luigi Stella 《Monthly notices of the Royal Astronomical Society》2008,384(4):1638-1648

Traditionally, studies aimed at inferring the distribution of birth periods of neutron stars are based on radio surveys. Here we propose an independent method to constrain the pulsar spin periods at birth based on their X-ray luminosities. In particular, the observed luminosity distribution of supernovae (SNe) poses a constraint on the initial rotational energy of the embedded pulsars, via the     correlation found for radio pulsars, and under the assumption that this relation continues to hold beyond the observed range. We have extracted X-ray luminosities (or limits) for a large sample of historical SNe observed with Chandra , XMM and Swift , which have been firmly classified as core-collapse SNe. We have then compared these observational limits with the results of Monte Carlo simulations of the pulsar X-ray luminosity distribution for a range of values of the birth parameters. We find that a pulsar population dominated by millisecond periods at birth is ruled out by the data.  相似文献   

Excess submillimetre emission from GRS 1915+105     

R. N. Ogley  S. J. Bell Burnell  R. P. Fender  G. G. Pooley  E. B. Waltman 《Monthly notices of the Royal Astronomical Society》2000,317(1):158-162

We present the first detections of the black hole X-ray binary GRS 1915+105 at submillimetre (submm) wavelengths. We clearly detect the source at 350 GHz in two epochs, with significant variability over the 24 h between epochs. Quasi-simultaneous radio monitoring indicates an approximately flat spectrum from 2 to 350 GHz, although there is marginal evidence for a minimum in the spectrum between 15 and 350 GHz. The flat spectrum and correlated variability imply that the submm emission arises from the same synchrotron source as the radio emission. This source is likely to be a quasi-steady partially self-absorbed jet, in which case these submm observations probe significantly closer to the base of the jet than do radio observations and may be used in future as a valuable diagnostic of the disc–jet connection in this source.  相似文献   

Orbital, precessional and flaring variability of Cygnus X-1     

C. Brocksopp  R. P. Fender  V. Larionov  V. M. Lyuty  A. E. Tarasov  G. G. Pooley  W. S. Paciesas  P. Roche 《Monthly notices of the Royal Astronomical Society》1999,309(4):1063-1073

We present the results of a 2.5-yr multiwavelength monitoring programme of Cygnus X-1, making use of hard and soft X-ray data, optical spectroscopy, UBVJHK photometry and radio data. In particular, we confirm that the 5.6-d orbital period is apparent in all wavebands, and note the existence of a wavelength dependence to the modulation, in the sense that higher energies reach minimum first. We also find a strong modulation at a period of 142±7 d, which we suggest is caused by precession and/or radiative warping of the accretion disc. Strong modulation of the hard and soft X-ray flux at this long period may not be compatible with simple models of an optically thin accretion flow and corona in the low state. We present the basic components required for more detailed future modelling of the system – including a partially optically thick jet, quasi-continuous in the low state, the base of which acts as the Comptonizing corona. In addition, we find that there are a number of flares that appear to be correlated in at least two wavebands and generally in more. We choose two of these flares to study in further detail, and find that the hard and soft X-rays are well correlated in the first, and that the soft X-rays and radio are correlated in the second. In general, the optical and infrared show similar behaviour to each other, but are not correlated with the X-rays or radio.  相似文献   

Opacity effects and shock-in-jet modelling of low-level activity in Cygnus X-3     

James C. A. Miller-Jones  Michael P. Rupen  Marc Türler  Elina J. Lindfors  Katherine M. Blundell  Guy G. Pooley 《Monthly notices of the Royal Astronomical Society》2009,394(1):309-322

We present simultaneous dual-frequency radio observations of Cygnus X-3 during a phase of low-level activity. We constrain the minimum variability time-scale to be 20 min at 43 GHz and 30 min at 15 GHz, implying source sizes of 2–4 au. We detect polarized emission at a level of a few per cent at 43 GHz which varies with the total intensity. The delay of ∼10 min between the peaks of the flares at the two frequencies is seen to decrease with time, and we find that synchrotron self-absorption and free–free absorption by entrained thermal material play a larger role in determining the opacity than absorption in the stellar wind of the companion. A shock-in-jet model gives a good fit to the light curves at all frequencies, demonstrating that this mechanism, which has previously been used to explain the brighter, longer lived giant outbursts in this source, is also applicable to these low-level flaring events. Assembling the data from outbursts spanning over two orders of magnitude in flux density shows evidence for a strong correlation between the peak brightness of an event, and the time-scale and frequency at which this is attained. Brighter flares evolve on longer time-scales and peak at lower frequencies. Analysis of the fitted model parameters suggests that brighter outbursts are due to shocks forming further downstream in the jet, with an increased electron normalization and magnetic field strength both playing a role in setting the strength of the outburst.  相似文献