Search Publications
In-depth studies of the NGC253 ULXs with XMM-Newton: remarkable variability in ULX1, and evidence for extended coronae
Barnard, R.
We examined the variability of three ultraluminous X-ray sources (ULXs) in the 2003, 110ks XMM-Newton observation of NGC253. Remarkably, we discovered ULX1 to be three times more variable than ULX2 in the 0.3-10 keV band, even though ULX2 is brighter. Indeed, ULX1 exhibits a power density spectrum that is consistent with the canonical high state o…
Associated spectral and temporal state transition of the bright ULXNGC1313 X-1
Rao, A. R.; Misra, R.; Dewangan, G. C. +1 more
Stellar mass black hole X-ray binaries exhibit X-ray spectral states which also have distinct and characteristic temporal properties. These states are believed to correspond to different accretion disc geometries. We present analysis of two XMM-Newton observations of the ultra-luminous X-ray source (ULX)NGC1313 X-1, which reveal that the system wa…
XMM-Newton and Swift observations prove GRB090709A to be a distant, standard, long GRB
Tiengo, A.; de Luca, A.; Götz, D. +4 more
GRB090709A is a long gamma-ray burst (GRB) discovered by Swift, featuring a bright X-ray afterglow as well as a faint infrared transient with very red and peculiar colours. The burst attracted a large interest because of a possible quasi-periodicity at P = 8.1s in the prompt emission, suggesting that it could have a different origin with respect t…
The first gigayear of bulge star formation in Virgo ellipticals: constraints from their globular cluster systems
Spitler, Lee R.
Data products from the Advanced Camera for Surveys Virgo cluster survey are used to understand the bulge star formation history in early-type galaxies at redshifts z >~2. A new technique is developed whereby observed high-redshift age-metallicity relationships are utilized to constrain the typical formation epochs of metal-rich or `bulge' globu…
Study of a homogeneous QSO sample: relations between the QSO and its host galaxy
Magain, P.; Letawe, G.; Letawe, Y.
We analyse a sample of 69 quasi-stellar objects (QSOs) which have been randomly selected in a complete sample of 104 QSOs (R <= 18,0.142 < z < 0.198,δ < 10°). 60 have been observed with the NTT/SUSI2 at La Silla, through two filters in the optical band (WB 655 and V 812), and the remaining nine are taken from archive data bases. The fi…
XMM-Newton and INTEGRAL study of the SFXT IGR J18483-0311 in quiescence: hint of a cyclotron emission feature?
Sidoli, L.; Ducci, L.; Bassani, L. +2 more
We report the results from archival XMM-Newton and INTEGRAL observations of the Supergiant Fast X-ray Transient (SFXT) IGR J18483-0311 in quiescence. The 18-60 keV hard X-ray behaviour of the source is presented here for the first time; it is characterized by a spectral shape (Γ ~ 2.5) similar to that during outburst activity, and the lowest measu…
A study of the massive star-forming region M8 using images from the Spitzer Infrared Array Camera
Kumar, Dewangan Lokesh; Anandarao, B. G.
We present photometry and images (3.6, 4.5, 5.8 and 8.0 µm) from the Spitzer Infrared Array Camera (IRAC) of the star-forming region Messier 8 (M8). The IRAC photometry reveals ongoing star formation in the M8 complex, with 64 class 0/I and 168 class II sources identified in several locations in the vicinity of submm gas cores/clumps. Nearly…
A faint extended cluster in the outskirts of NGC 5128: evidence of a low mass accretion
Rejkuba, M.; Mouhcine, M.; Ibata, R. +1 more
We report the discovery of an extended globular cluster in a halo field in Centaurus A (NGC 5128), situated from the centre of that galaxy, imaged with the Advanced Camera for Surveys on board the Hubble Space Telescope. At the distance of the galaxy, the half-light radius of the cluster is rh ~ 17pc, placing it among the largest globul…
Weighing dark matter haloes with gravitationally lensed supernovae
Goobar, A.; Hook, I.; Mörtsell, E. +2 more
High-redshift Type Ia supernovae (SNe Ia) are likely to be gravitationally lensed by dark matter haloes of galaxies in the foreground. Since SNe Ia have very small dispersion after light-curve shape and colour corrections, their brightness can be used to measure properties of the dark matter haloes via gravitational magnification. We use observati…
Multifrequency nature of the 0.75 mHz feature in the X-ray light curves of the nova V4743 Sgr
Ness, J. -U.; Dobrotka, A.
We present timing analyses of eight X-ray light curves and one optical/UV light curve of the nova V4743 Sgr (2002) taken by Chandra and XMM-Newton on the following days after outburst: 50 (early hard emission phase), 180, 196, 302, 371, 526 [super soft source (SSS) phase], and 742 and 1286 (quiescent emission phase). We have studied the multifrequ…