Search Publications
Early SPI/INTEGRAL measurements of 511 keV line emission from the 4th quadrant of the Galaxy
Strong, A. W.; Gehrels, N.; Knödlseder, J. +18 more
We report the first measurements of the 511 keV line emission from the Galactic Centre (GC) region performed with the spectrometer SPI on the space observatory INTEGRAL (International Gamma-Ray Astrophysics Laboratory). Taking into account the range of spatial distribution models which are consistent with the data, we derive a flux of 9.9+4.7…
Distances and ages of NGC 6397, NGC 6752 and 47 Tuc
Grundahl, F.; Clementini, G.; Bragaglia, A. +4 more
New improved distances and absolute ages for the Galactic globular clusters NGC 6397, NGC 6752, and 47 Tuc are obtained using the Main Sequence Fitting Method. We derived accurate estimates of reddening and metal abundance for these three clusters using a strictly differential procedure, where the Johnson B-V and Strömgren b-y colours and UVES hig…
Abundances for metal-poor stars with accurate parallaxes. I. Basic data
Barbieri, M.; Claudi, R.; Carretta, E. +2 more
We present element-to-element abundance ratios measured from high dispersion spectra for 150 field subdwarfs and early subgiants with accurate Hipparcos parallaxes (errors <20%). For 50 stars new spectra were obtained with the UVES on Kueyen (VLT UT2), the McDonald 2.7 m telescope, and SARG at TNG. Additionally, literature equivalent widths wer…
The INTEGRAL/IBIS scientific data analysis
Foschini, L.; David, P.; Bird, A. J. +6 more
The gamma-ray astronomical observatory INTEGRAL, succesfully launched on 17th October 2002, carries two large gamma-ray telescopes. One of them is the coded-mask imaging gamma-ray telescope onboard the INTEGRAL satellite (IBIS) which provides high-resolution (~12') sky images of 29degx29deg in the energy range from 15 keV to …
Reconstruction of solar irradiance variations in cycle 23: Is solar surface magnetism the cause?
Solanki, S. K.; Krivova, N. A.; Unruh, Y. C. +1 more
A model of solar irradiance variations is presented which is based on the assumption that solar surface magnetism is responsible for all total irradiance changes on time scales of days to years. A time series of daily magnetograms and empirical models of the thermal structure of magnetic features (sunspots, faculae) are combined to reconstruct tot…
Vertical distribution of Galactic disk stars. I. Kinematics and metallicity
Soubiran, C.; Siebert, A.; Bienaymé, O.
Nearly 400 Tycho-2 stars have been observed in a 720 square degree field in the direction of the North Galactic Pole with the high resolution echelle spectrograph ELODIE. Absolute magnitudes, effective temperatures, gravities and metallicities have been estimated, as well as distances and 3D velocities. Most of these stars are clump giants and spa…
Multiplicity among solar-type stars. III. Statistical properties of the F7-K binaries with periods up to 10 years
Arenou, F.; Udry, S.; Mayor, M. +1 more
Two CORAVEL radial velocity surveys - one among stars in the solar neighbourhood, the other in the Pleiades and in Praesepe - are merged to derive the statistical properties of main-sequence binaries with spectral types F7 to K and with periods up to 10 years. A sample of 89 spectroscopic orbits was finally obtained. Among them, 52 relate to a fre…
Determination of the gas-to-dust ratio in nearby dense clouds using X-ray absorption measurements
Grosso, N.; Montmerle, T.; Feigelson, E. D. +3 more
We present a comparison of the gas and dust properties of the dense interstellar matter in six nearby star-forming regions (d<500 pc): rho Oph, Cha I, R CrA, IC 348, NGC 1333, and Orion. We measure from Chandra and XMM-Newton observations the X-ray absorption toward pre-main sequence stars (PMS) without accretion disks (i.e., Class III sources)…
Distances to nearby galaxies in Sculptor
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +7 more
We present an analysis of Hubble Space Telescope/WFPC2 images of nine nearby galaxies in Sculptor. We derive their distances from the luminosity of the tip of the red giant branch stars with a typical accuracy of ~ 12%. Their distances are 4.21 Mpc (Sc 22), 4.92 Mpc (DDO 226), 3.94 Mpc (NGC 253), 3.40 Mpc (KDG 2), 3.34 Mpc (DDO 6), 3.42 Mpc (ESO 5…
Steps toward interstellar silicate mineralogy. VII. Spectral properties and crystallization behaviour of magnesium silicates produced by the sol-gel method
Mutschke, H.; Henning, Th.; Posch, Th. +2 more
Amorphous silicate particles are generally assumed to be the main dust component in the envelopes of oxygen-rich evolved stars and may be considered the precursors of the pure crystalline enstatite and forsterite particles detected by ISO. We present optical constants in the broad wavelength range 0.2-500 mu m for a unique series of pure amorphous…