Search Publications
Spectral variability of GX339-4 in a hard-to-soft state transition
Belloni, T.; Ubertini, P.; Malzac, J. +2 more
We report on INTEGRAL observations of the bright black hole transient GX339-4 performed during the period 2004 August-September, including the fast transition (10h) observed simultaneously with INTEGRAL and RXTE on August 15 and previously reported. Our data cover three different spectral states, namely hard/intermediate state (HIMS), soft/interme…
X-ray spectra from magnetar candidates - II. Resonant cross-sections for electron-photon scattering in the relativistic regime
Zane, S.; Nobili, L.; Turolla, R.
Recent models of spectral formation in magnetars called renewed attention on electron-photon scattering in the presence of ultrastrong magnetic fields. Investigations presented so far mainly focused on mildly relativistic particles and magnetic scattering was treated in the non-relativistic (Thomson) limit. This allows for consistent spectral calc…
The 2008 May burst activation of SGR1627-41
Sakamoto, T.; Tiengo, A.; de Luca, A. +16 more
In 2008 May, the soft gamma-ray repeater (SGR) SGR1627-41 resumed its bursting activity after nearly a decade of quiescence. After detection of a bright burst, Swift pointed its X-ray telescope in the direction of the source in less than five hours and followed it for over five weeks. In this Letter, we present an analysis of the data from these S…
The kinematic footprints of five stellar streams in Andromeda's halo
Tanvir, N.; Rich, R. M.; Koch, A. +12 more
We present a spectroscopic analysis of five stellar streams (`A', `B', `Cr', `Cp' and `D') as well as the extended star cluster, EC4, which lies within Stream`C', all discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey. These spectroscopic results were initially serendipitous, making use of our existing observation…
The faint and extremely red K-band-selected galaxy population in the DEEP2/Palomar fields
Conselice, C. J.; Bundy, K.; Lotz, J. +3 more
We present in this paper an analysis of the faint and red near-infrared (NIR) selected galaxy population found in NIR imaging from the Palomar Observatory Wide-Field Infrared Survey. This survey covers 1.53 deg2 to 5σ detection limits of Kvega = 20.5-21 and Jvega = 22.5, and overlaps with the DEEP2 spectroscopic re…
X-ray variability of the Seyfert 1 Markarian 335: power spectrum and time lags
Arévalo, P.; McHardy, I. M.; Summons, D. P.
To investigate further the comparison between active galactic nuclei (AGN) and black hole X-ray binaries, we have studied the main X-ray variability properties of the Seyfert 1 galaxy Mrk 335. We put particular emphasis on the X-ray time lags, which is a potentially important diagnostic of physical models. From a 100 ks observation by XMM-Newton, …
On the nature of unabsorbed Seyfert 2 galaxies
Nandra, Kirpal; Brightman, Murray
We present an analysis of six 12µm selected Seyfert 2 galaxies that have been reported to be unabsorbed in the X-ray. By comparing the luminosities of these galaxies in the mid-infrared (12µm), optical ([OIII]) and hard X-ray (2-10keV), we show that they are all underluminous in the 2-10keV X-ray band. Four of the objects exhibit X-ray…
Anatomy of a young massive star cluster: NGC 1569-B
Larsen, S. S.; Gallagher, J. S.; Origlia, L. +1 more
We present new H-band echelle spectra, obtained with the NIRSPEC spectrograph at Keck II, for the massive star cluster `B' in the nearby dwarf irregular galaxy NGC 1569. From spectral synthesis and equivalent width measurements, we obtain abundances and abundance patterns. We derive an Fe abundance of [Fe/H] = -0.63 +/- 0.08, a supersolar [α/Fe] a…
Structural parameters for globular clusters in NGC 5128 - III. ACS surface brightness profiles and model fits
Forbes, Duncan A.; Barmby, Pauline; Harris, William E. +2 more
We present internal surface brightness profiles, based on Hubble Space Telescope/ACS imaging in the F606W bandpass, for 131 globular cluster (GC) candidates with luminosities L ~= 104-3 × 106Lsolar in the giant elliptical galaxy NGC 5128. Several structural models are fitted to the profile of each cluster and combi…
A search for the progenitors of two TypeIa Supernovae in NGC 1316
Maoz, Dan; Mannucci, Filippo
Recent evidence of a young progenitor population for many TypeIa supernovae (SNeIa) raises the possibility that evolved intermediate-mass progenitor stars may be detected in pre-explosion images. NGC 1316, a radio galaxy in the Fornax cluster, is a prolific producer of SNeIa, with four detected since 1980. We analyse Hubble Space Telescope (HST) p…