Search Publications
Maximum-likelihood detection of sources among Poissonian noise
Stewart, I. M.
A maximum likelihood (ML) technique for detecting compact sources in images of the X-ray sky is examined. Such images, in the relatively low exposure regime accessible to present X-ray observatories, exhibit Poissonian noise at background flux levels. A variety of source detection methods are compared via Monte Carlo, and the ML detection method i…
Multiwavelength analysis of a solar quiet region
Heinzel, P.; Schwartz, P.; Tziotziou, K. +1 more
Context: We examine oscillatory phenomena in a solar network region from multi-wavelength observations obtained by the ground-based Dutch Open Telescope (DOT) and by the Coronal Diagnostic Spectrometer (CDS) on the spacecraft Solar and Heliospheric Observatory (SoHO). The observations were obtained during a coordinated observing campaign in Octobe…
Abundances in planetary nebulae: NGC 2792
Pottasch, S. R.; Bernard-Salas, J.; Surendiranath, R. +1 more
The mid-infrared spectrum of the rather circular planetary nebula
The FERRUM project: transition probabilities for forbidden lines in [Fe II] and experimental metastable lifetimes
Nilsson, H.; Hartman, H.; Gurell, J. +5 more
Context: Accurate transition probabilities for forbidden lines are important diagnostic parameters for low-density astrophysical plasmas. In this paper we present experimental atomic data for forbidden [ion{Fe}{ii}] transitions that are observed as strong features in astrophysical spectra.
Aims: We measure lifetimes for the 3d^6(^3G)4s a ^4G{…
Oxygen in dense interstellar gas. The oxygen abundance of the star forming core ρ Ophiuchi A
Liseau, R.; Justtanont, K.
Context: Oxygen is the third most abundant element in the universe, but its chemistry in the interstellar medium is still not understood well.
Aims: To critically examine the entire oxygen budget, we initially attempt to estimate the abundance of atomic oxygen, O, in the only region where molecular oxygen, O{2}, has been detected to date.
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An extreme EXO: a type 2 QSO at z = 1.87
Akiyama, M.; Carrera, F. J.; Watson, M. G. +6 more
Aims: We aim to understand the multi-wavelength properties of 2XMM J123204+215255, the source with the most extreme X-ray-to-optical flux ratio amongst a sample of bright X-ray selected EXOs drawn from a cross-correlation of the 2XMMp catalogue with the SDSS-DR5 catalogue.
Methods: We use 2XMMp X-ray data, SDSS-DR5, NOT and UKIRT optical/NIR p…
A FEROS spectroscopic study of the extreme O supergiant He 3-759
Crowther, P. A.; Evans, C. J.
We present a study of the extreme O-type supergiant He 3-759 using new high-resolution FEROS data, revealing that it is a near spectroscopic twin of HD 151804 (O8 Iaf). We investigate the extinction towards He 3-759 using a variety of methods, revealing AV ∼ 4.7^m. If we assume He 3-759 has an identical absolute K-band magnitude to HD 1…
Neutral absorber dips in the periodic burster LMXB XB 1323-619 from Suzaku
Church, M. J.; Dotani, T.; Bałucińska-Church, M. +1 more
We present results of an observation with Suzaku of the dipping, periodic bursting low mass X-ray binary XB 1323-619. Using the energy band 0.8-70 keV, we show that the source spectrum is well-described as the emission of an extended accretion disk corona, plus a small contribution of blackbody emission from the neutron star. The dip spectrum is w…
INTEGRAL observations of the Perseus cluster
Paltani, S.; Eckert, D.
We present the results of a 500 ks observation of the Perseus cluster with INTEGRAL, with the aim of investigating the possible diffuse non-thermal component detected in a previous Chandra observation. In the 3-20 keV band with the JEM-X instrument, we detect the source with high significance and resolve it spatially. Above 20 keV with IBIS/ISGRI,…
Cluster and cluster galaxy evolution history from IR to X-ray observations of the young cluster RX J1257.2+4738 at z = 0.866
Ilbert, O.; Adami, C.; Gavazzi, R. +8 more
Context: The cosmic time around the z ~ 1 redshift range appears crucial in the cluster and galaxy evolution, since it is probably the epoch of the first mature galaxy clusters. Our knowledge of the properties of the galaxy populations in these clusters is limited because only a handful of z ~ 1 clusters are presently known.
Aims: In this fram…