Search Publications
The X-ray coronae of the two brightest galaxies in the Coma cluster
Simionescu, A.; Churazov, E.; Fabian, A. C. +4 more
We use deep Chandra X-ray Observatory observations to examine the coronae of the two brightest cluster galaxies in the Coma cluster of galaxies, NGC 4874 and NGC 4889. We find that NGC 4889 hosts a central depression in X-ray surface brightness consistent with a cavity or pair of cavities of radius 0.6 kpc. If the central cavity is associated with…
Symbiotic stars in OGLE data - I. Large Magellanic Cloud systems
Udalski, A.; Pietrukowicz, P.; Masetti, N. +10 more
Symbiotic stars are long-orbital-period interacting binaries characterized by extended emission over the whole electromagnetic range and by complex photometric and spectroscopic variability. In this paper, the first of a series, we present Optical Gravitational Lensing Experiment (OGLE) light curves of all the confirmed symbiotic stars in the Larg…
Discovery of a correlation between the frequency of the mHz quasi-periodic oscillations and the neutron-star temperature in the low-mass X-ray binary 4U 1636-53
Méndez, Mariano; Altamirano, Diego; Lyu, Ming
We detected millihertz quasi-periodic oscillations (QPOs) in an XMM-Newton observation of the neutron-star low-mass X-ray binary 4U 1636-53. These QPOs have been interpreted as marginally stable burning on the neutron-star surface. At the beginning of the observation the QPO was at around 8 mHz, together with a possible second harmonic. About 12 k…
Hard X-ray emission of Sco X-1
Tsygankov, Sergey S.; Revnivtsev, Mikhail G.; Krivonos, Roman A. +1 more
We study hard X-ray emission of the brightest accreting neutron star Sco X-1 with INTEGRAL observatory. Up to now INTEGRAL have collected ∼4 Ms of deadtime corrected exposure on this source. We show that hard X-ray tail in time average spectrum of Sco X-1 has a power-law shape without cutoff up to energies ∼200-300 keV. An absence of the high ener…
Spectral detection of multiple stellar populations in z ∼ 1 early-type galaxies
Longhetti, M.; Gargiulo, A.; Saracco, P. +2 more
We present a spectroscopic analysis based on measurements of two mainly age-dependent spectrophotometric indices in the 4000 Å rest-frame region, i.e. H+K(Ca II) and Δ4000, for a sample of 15 early-type galaxies (ETGs) at 0.7 < zspec < 1.1, morphologically selected in the GOODS-South field. Ages derived from the two different indi…
Swift J2218.4+1925: a new hard-X-ray-selected polar observed with XMM-Newton
Mukai, K.; de Martino, D.; Bernardini, F. +1 more
Swift J2218.4+1925, a hard-X-ray source detected by Swift Burst Alert Telescope (BAT), has been proposed as a candidate magnetic cataclysmic variable of the polar type from optical spectroscopy. Using XMM-Newton we perform detailed timing and spectral analysis with simultaneous X-ray (0.3-10 keV) and optical B-band data. We complement the spectral…
Spectral state transitions of the Ultraluminous X-ray Source IC 342 X-1
Kaaret, P.; Mushotzky, R. F.; Miller, N. +6 more
We observed the Ultraluminous X-ray Source (ULX) IC 342 X-1 simultaneously in X-ray and radio with Chandra and the JVLA to investigate previously reported unresolved radio emission coincident with the ULX. The Chandra data reveal a spectrum that is much softer than observed previously and is well modelled by a thermal accretion disc spectrum. No s…
The ionized nebula surrounding the red supergiant W26 in Westerlund 1
Drake, Jeremy J.; Barlow, Michael J.; Wright, Nicholas J. +7 more
We present Hα images of an ionized nebula surrounding the M2-5Ia red supergiant (RSG) W26 in the massive star cluster Westerlund 1. The nebula consists of a circumstellar shell or ring ∼0.1 pc in diameter and a triangular nebula ∼0.2 pc from the star that in high-resolution Hubble Space Telescope images shows a complex filamentary structure. The e…
HST optical polarimetry of the Vela pulsar and nebula
Mignani, R. P.; Moran, P.; Shearer, A.
Polarization measurements of pulsars offer a unique insight into the geometry of the emission regions in the neutron star magnetosphere. Therefore, they provide observational constraints on the different models proposed for the pulsar emission mechanisms. Optical polarization data of the Vela pulsar was obtained from the Hubble Space Telescope (HS…
Resolving different sources of fast X-ray variability of the dwarf nova RU Peg in quiescence
Ness, J. -U.; Dobrotka, A.; Mineshige, S.
We analysed an X-ray light curve of the dwarf nova RU Peg taken by XMM-Newton with a duration of 46300 s. The power density spectrum has a complicated shape with two red noise and two white noise components, indicating the presence of two turbulent regions. We developed a statistical `toy model' to study light curves with variability produced by a…