Search Publications

On the complex X-ray structure tracing the motion of Geminga

Caraveo, P. A.; Bignami, G. F.; de Luca, A. +2 more

A deep (100 ks) XMM-Newton observation of Geminga has shown two faint tails of diffuse X-ray emission, extending for ~2' behind the pulsar, well aligned with the proper motion (PM) direction. We report here on a recent ~20 ks Chandra observation, which unveils a new structure, ~25'' long and ~5'' thick, starting at the pulsar position and perfectl…

Comments on the amplitude-phase relationship of asteroid lightcurves. Effects of topography, surface scattering properties, and obliquity

Rodrigo, R.; Gutiérrez, P. J.; Ortiz, J. L. +2 more

Aims.We present a theoretical study on the amplitude-phase relationship (APR) for lightcurves of simulated asteroids.
Methods: .In support of the Rosetta (ESA) mission, we developed a numerical model for the investigation of the light reflectance properties of asteroidal bodies. The code is able to deal with irregular and chemically inhomogene…

Unveiling the nature of the highly absorbed X-ray source SAX J1748.2-2808 with XMM-Newton

Mereghetti, S.; Parmar, A. N.; Sidoli, L. +2 more

We report on the results of an EPIC XMM-Newton observation of the faint source SAX J1748.2-2808 and the surrounding field. This source was discovered during the BeppoSAX Galactic center survey performed in 1997-1998. A spatial analysis resulted in the detection of 31 sources within the EPIC field of view. SAX J1748.2-2808 is clearly resolved into …

The old globular cluster system of the dIrr galaxy NGC 1427A in the Fornax cluster

Infante, L.; Hilker, M.; Georgiev, I. Y. +5 more

We present a study of the old globular cluster (GC) population of the dwarf irregular galaxy NGC 1427A using multi-wavelength VLT observations in U,B,V,I, Hα and J bands under excellent observing conditions. We applied color and size selection criteria to select old GC candidates and made use of archival ACS images taken with the Hubble Space Tele…

Surface-brightness fluctuations in stellar populations. IAC-star models for the optical and near-IR wavelengths

Marín-Franch, A.; Aparicio, A.

Aims.A new theoretical calibration of surface-brightness fluctuations (SBF) for single age, single metallicity stellar populations is presented for the optical and near-IR broad-band filters, as well as for the HST WFPC2 and ACS filters.
Methods: .The IAC-star code is used. Two Padua and the Teramo stellar evolution libraries have been conside…

Filling the infrared gap: ISO observations of 1 Jy BL Lacertae objects

Giommi, P.; Ábrahám, P.; Moór, A. +2 more

Aims.The large majority of BL Lacertae objects belonging to the 1 Jy sample, the class prototype for radio-selected sources, are thought to emit most of their synchrotron power in the far infrared band. Ironically, this spectral region is very sparsely sampled, with only a minority of the objects having IRAS data (most of them being upper limits o…

GMRT observations of the field of INTEGRAL X-ray sources - I

Durouchoux, P.; Manchanda, R. K.; Pandey, M. +2 more

Since its launch the INTEGRAL observatory has discovered a variety of hard X-ray sources in the Galactic plane. Using GMRT, we have made repeated observations of these sources to search for the radio counterparts of seventeen of them at low frequencies. The source positions were taken from the various ATEL and IAUC announcements reporting their di…

Chemical abundances of 32 mildly metal-poor stars

Zhao, G.; Zhang, H. W.

Context: .The formation scenario of the Galactic thick disk is an unresolved problem. Chemical abundances in long-lived dwarf stars of the thin and thick disks provide information of the Galactic disk formation.Aims.We present photospheric abundances of the O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Ni, and Ba elements for 32 mildly metal-poor star…

Thermal emission of spherical spinning ring particles. The standard model

Leyrat, C.; Ferrari, C.

A simple new thermal model was developed to study the effects of the spherical shape of ring particles, of their finite thermal inertia, and of their spinning properties on the rings thermal emission. Ring particles are assumed to be scattered in a monolayer,

a structure that might exist at least in the population of large particles embedded …

Accurate photometry of extended spherically symmetric sources

Gieles, M.; de Grijs, R.; Anders, P.

We present a new method to derive reliable photometry of extended spherically symmetric sources from HST images (WFPC2, ACS/WFC and NICMOS/NIC2 cameras), extending existing studies of point sources and marginally resolved sources. We develop a new approach to accurately determine intrinsic sizes of extended spherically symmetric sources, such as s…