Search Publications
The ancient stellar population of M 32: RR Lyrae variable stars confirmed
Saha, A.; Clementini, G.; Contreras Ramos, R. +2 more
Using archival multi-epoch ACS/WFC images in the F606W and F814W filters of a resolved stellar field in Local Group dwarf elliptical galaxy M 32 we have made an accurate colour-magnitude diagram and a careful search for RR Lyr variable stars. We identified 416 bona fide RR Lyr stars over our field of view, and their spatial distribution shows a ri…
The horizontal branch luminosity vs. metallicity in M 31 globular clusters
Cacciari, C.; Bellazzini, M.; Galleti, S. +3 more
Context. Thanks to the outstanding capabilites of the HST, our current knowledge about the M 31 globular clusters (GCs) is similar to our knowledge of the Milky Way GCs in the 1960s - 1970s, which set the basis for studying the halo and galaxy formation using these objects as tracers, and established their importance in defining the cosmic distanc…
Timing properties of gamma-ray bursts detected by SPI-ACS detector onboard INTEGRAL
Savchenko, V.; Courvoisier, T. J. -L.; Neronov, A.
Aims: We study timing properties of a large sample of gamma-ray bursts (GRB) detected by the anti-coincidence shield (ACS) of the SPI spectrometer of INTEGRAL telescope.
Methods: We identify GRB-like events in the SPI-ACS data. The data set under investigation is the history of count rate of the SPI-ACS detector recorded with a binning o…
The reawakening of the sleeping X-ray pulsar XTE J1946+274
Wilms, J.; Ferrigno, C.; Pottschmidt, K. +9 more
We report on a series of outbursts of the high-mass X-ray binary XTE J1946+274 in 2010/2011 observed with INTEGRAL, RXTE, and Swift. We discuss possible mechanisms resulting in the extraordinary outburst behavior of this source. The X-ray spectra can be described by standard phenomenological models, enhanced by an absorption feature of unknown ori…
An updated catalog of OH-maser-emitting planetary nebulae
Gómez, J. F.; Miranda, L. F.; Suárez, O. +1 more
Aims: We studied the characteristics of planetary nebulae (PNe) that show both OH maser and radio continuum emission (hereafter OHPNe). These have been proposed to be very young PNe, and therefore, they could be key objects for understanding the formation and evolution of PNe.
Methods: We consulted the literature searching for interferom…
Spatially resolved X-ray spectroscopy and modeling of the nonthermal emission of the pulsar wind nebula in G0.9+0.1
Stegmann, C.; Eger, P.; Schöck, F. M. +3 more
Aims: We performed a spatially resolved spectral X-ray study of the pulsar wind nebula (PWN) in the supernova remnant G0.9+0.1. Furthermore, we modeled its nonthermal emission in the X-ray and very high-energy (VHE, E > 100 GeV) γ-ray regime.
Methods: Using Chandra ACIS-S3 data, we investigated the east-west dependence of the spectral…
Statistics and implications of substructure detected in a representative sample of X-ray clusters
Böhringer, H.; Smith, G. P.; Chon, G.
We present a morphological study of 35 X-ray luminous galaxy clusters at 0.15 < z < 0.3, selected in a similar manner to the Local Cluster Substructure Survey (LoCuSS), for which deep XMM-Newton observations are available. We characterise the structure of the X-ray surface brightness distribution of each cluster by measuring both their power…
High-velocity stars in the cores of globular clusters: the illustrative case of NGC 2808
Kruijssen, J. M. D.; Kissler-Patig, M.; de Zeeuw, P. T. +7 more
Context. We report the detection of five high-velocity stars in the core of the globular cluster NGC 2808. The stars lie on the red giant branch and show total velocities between 40 and 45 km s-1. For a core velocity dispersion σc = 13.4 km s-1, this corresponds to up to 3.4σc. These velocities are close…
Sub-millimetre spectroscopy of Saturn's trace gases from Herschel/SPIRE
Fletcher, L. N.; Hartogh, P.; Lellouch, E. +15 more
Aims: We provide an extensive new sub-millimetre survey of the trace gas composition of Saturn's atmosphere using the broad spectral range (15-51 cm-1) and high spectral resolution (0.048 cm-1) offered by Fourier transform spectroscopy by the Herschel/SPIRE instrument (Spectral and Photometric Imaging REceiver). Observat…
Searching for X-ray emission from AGB stars
Montez, R.; Kastner, J.; Ramstedt, S. +1 more
Context. Magnetic fields have been measured around asymptotic giant branch (AGB) stars of all chemical types using maser polarization observations. If present, a large-scale magnetic field would lead to X-ray emission, which should be observable using current X-ray observatories.
Aims: The aim is to search the archival data for AGB stars that…