Search Publications

Relationship between decrease of net magnetic flux and solar major events

Liu, Y.; Tian, L. R.

Using the full disk magnetograms taken by SOHO/MDI, we studied the evolution of magnetic fluxes in the line-of-sight for twelve solar active regions in the 23rd cycle, which produced strong solar activities. It is measured that the fluxes of these regions were appreciably imbalanced when they moved past the central meridian, where reliable measure…

Anomalously bright UV lines of Fe II as a probe of gas condensations in the vicinity of hot stars

Johansson, S.; Letokhov, V. S.

Two UV lines of Fe II at 2507/2509 Å are extremely bright in spatially resolved HST/STIS spectra of dense gas condensations (the so called Weigelt blobs) close to the central star of η Carinae. The lines also appear unresolved in HST/FOS spectra of the star AE And. Under normal conditions the lines should hardly be observable. Based on recent stud…

The in-flight background of IBIS/PICsIT

Di Cocco, G.; Malizia, A.; Bassani, L. +3 more

The PICsIT instrument is the high-energy imaging detector of IBIS on board INTEGRAL and comprises 4096 individual scintillator elements each working in the energy range from about 175 keV to 10 MeV. Images of the sky are created using the coded aperture technique wherein each point in the detection plane contributes to the final image. For this re…

IBIS ground calibration

Di Cocco, G.; Malaguti, G.; Bird, A. J. +13 more

We present an overview of results obtained from IBIS ground calibrations. The spectral and spatial characteristics of the detector planes and surrounding passive materials have been determined through a series of calibration campaigns. Measurements of pixel gain, energy resolution, detection uniformity, efficiency and imaging capability are presen…

Spectroscopic mode identification for the slowly pulsating B star HD 147394

Mathias, P.; Aerts, C.; Briquet, M. +2 more

We present ground-based high-resolution high S/N spectra of the slowly pulsating B star HD 147394. Two frequencies are clearly found in the moments of the Si II 4128-4130 doublet: f₁=0.8008 c d^-1 and f₂=0.7813 c d^-1. The frequency f₁ is also found in the HIPPARCOS data. A third frequency is al…

JEM-X observations of the Be/X-ray binary EXO 2030+375

Reig, P.; Kretschmar, P.; Lund, N. +3 more

We have used data from the Joint European Monitor (JEM-X) to perform an X-ray spectral and timing analysis of the 42-s transient pulsar EXO 2030+375 during an X-ray outburst. X-ray pulsations are clearly detected with an average pulse period of 41.66+/-0.05 s and an average pulse fraction of 60%. The profile of the energy spectrum did not change a…

X-ray observations of the Crab Pulsar and Nebula with JEM-X on INTEGRAL

Walter, R.; Schmidt, M.; Westergaard, N. J. +8 more

The Crab pulsar is the best studied rotation powered pulsar. We report the results obtained in the 3-35 keV energy band with the X-ray monitor, JEM-X, on ESAs recently launched gamma -ray mission, INTEGRAL.

Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the …

Deriving effective sunspot temperatures from SOHO/VIRGO irradiance measurements. A starspot modelling approach

Hanslmeier, A.; Eker, Z.; Otruba, W. +2 more

A method is developed to obtain mean effective sunspot temperatures from satellite irradiance deficits. Using a formalism derived from a star spot modelling approach, this method only requires accurate positions and areas of sunspots - but not intensities. The method is applied to SOHO/VIRGO spectral solar irradiance (SSI) at 402, 500, and 862 nm …

Outbursts in the Be star HR 2501

Carrier, F.; Burki, G.

The Be star HR 2501 was monitored in photometry, from 1978 to 1998 in the GENEVA system and from 1990 to 1992 by the HIPPARCOS satellite, and in spectroscopy from 1998 to 2001 by using the CORALIE spectrograph. Several mostly unrelated periods or time scales characterize the variability of HR 2501. First, the …

Optical design of the Optical Monitoring Camera (OMC) of INTEGRAL

Mas-Hesse, J. M.; Renotte, E.; Rochus, P. +5 more

The Optical Monitoring Camera (OMC) will observe the optical emission from the main targets of the gamma-ray instruments onboard the ESA mission INTEGRAL. The OMC is based on a refractive optics with an aperture of 50 mm focused onto a large format CCD (1024 x 2048 pixels), and a field of view of 5degrx5 degr . This paper describes the design of t…