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Quiet-Sun variability observed with SUMER and CDS
Solanki, S. K.; Brković, A.; Rüedi, I.
Brightness variations of solar features are investigated using time series of images and spectra of quiet-Sun regions at disc centre obtained with the Coronal Diagnostic Spectrometer (CDS) and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument onboard the SOHO spacecraft. Ultraviolet emission lines sampling temperatures of …
Constraints on ion outflow speeds and electron distribution function in the corona derived from sumer electron temperatures and SWICS ion fractions
Esser, R.; Edgar, R. J.
It has been a puzzle for quite some time that spectroscopic measurements in the inner corona indicate electron temperatures far too low to produce the ion fractions observed in the in situ solar wind. In the present paper we show that in order to reconcile the two sets of measurements, a number of conditions have to exist in the inner corona: 1) t…
On the Low-Mass End of the Globular Cluster Luminosity Function
Smith, Graeme H.; Burkert, Andreas
The low-mass globular cluster luminosity function (GCLF) in the Milky Way and in two elliptical galaxies is investigated. We find that the power-law slope of the Milky Way GCLF depends on the cluster concentration c. The origin of this trend is explored within the framework of a GC mass-loss model. It is also found that the low-mass GCLF of the Mi…
Influence of coronal mass ejection on geomagnetic activity during 1988–1993
Shrivastava, Pankaj Kumar; Singh, G. N.
The most rapid and dramatic evolution in the solar corona occurs in events now known as Coronal Mass Ejections (CMEs). There have considerable importance for our understanding of the evolution of the mass and energy injected into the interplanetary medium. In this work, we have studied the relation of CMEs with geomagnetic activity for the period …
Contribution to the search for binaries among Am stars - III. HD 7119: a double-lined spectroscopic binary and a triple system
Udry, S.; Ginestet, N.; Prieur, J. -L. +1 more
Radial velocity observations of HD 7119 with the CORAVEL instrument at Observatoire de Haute-Provence are reported. Known as an Amδδ Del metallic-line star, HD 7119 was included in our spectroscopic survey of Am-type stars, the purpose of which was to determine the frequency of binaries in this stellar family. This object is found to be a double-l…
Detecting low amplitude periodicities with HIPPARCOS
Kallinger, T.; Weiss, W. W.
The HIPPARCOS and TYCHO catalogues have proven to be a very powerful source for detection of variability in stars. The photometric errors for individual measurements are typically of the order of a few millimagnitudes. Amplitudes for periodic variability of stars and based on HIPPARCOS data are published which are of the same order. An example cou…
A Polarimetric Survey for Dust in 47 Tucanae
Forte, Juan C.; Vega, E. Irene; Cellone, Sergio A. +3 more
We present linear polarization measurements in the V band for 77 stars in the field of the globular cluster 47 Tucanae (NGC 104) and for 14 regions free of bright stars, located along an elliptical isophotal contour of the cluster, as well as UBVRI measurements for the cluster nucleus. The observations show variable foreground polarization that, o…
The multimode pulsation of the delta Scuti star V784 Cassiopeae
Thomson, J. R.; Derekas, A.; Garrido, R. +5 more
We present an analysis of new Johnson and Strömgren photometric and medium-resolution spectroscopic observations of the delta Scuti type variable star V784 Cassiopeae. The data were obtained in three consecutive years between 1999 and 2001. The period analysis of the light curve resulted in the detection of four frequencies ranging from 9.15 d
Observations of shock acceleration signatures by Ulysses: the 04:08:16, day147, 1991 UT shock
Sarris, E. T.; Anagnostopoulos, G. C.; Marhavilas, P. K.
We analyze the acceleration signatures of energetic ions (E>50keV) and electrons (E>30keV) observed on day 147, 1991 UT in the vicinity of the surface of a fast-mode hydromagnetic shock, using fine time resolution measurements by the HI-SCALE instrument onboard the Ulysses spacecraft. The observations present strong evidence for the accelera…
Timing analysis of the core of the Crab-like SNR G21.5-0.9
Mereghetti, S.; La Palombara, N.
The Crab-like SNR G21.5-0.9 was observed in the X-ray band (0.5-10 keV) by the XMM-Newton satellite for over 100 ks. The large effective area of the EPIC instrument has allowed us to perform a deep search for pulsations from the central core of . No pulsations were found with upper limits on the pulsed fraction between 7.5% and 40% (depending on f…