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The IMF of open star clusters with Tycho-2
Geffert, M.; Sanner, J.
We studied the fields of nine nearby open star clusters based on the Tycho-2 catalogue. We determined membership probabilities for the stars in the cluster fields from the stellar proper motions and used the Tycho-2 photometry to compute the initial mass function (IMF) of the clusters from the main sequence turn-off point down to approx. 1 M_sun. …
Magnetic Flux Cancellation Observed in the Sunspot Moat
Wang, Haimin; Yurchyshyn, Vasyl B.
In this paper we study the evolution of magnetic fields of a 1F/2.4C solar flare and following magnetic flux cancellation. The data are Big Bear Solar Observatory and SOHO/MDI observations of active region NOAA 8375. The active region produced a multitude of subflares, many of them being clustered along the moat boundary in the area with mixed pol…
RR Lyrae Variables in the Globular Clusters of M31: A First Detection of Likely Candidates
Clementini, G.; Cacciari, C.; Bellazzini, M. +3 more
The purpose of this Letter is to show that RR Lyrae variables exist and can be detected in M31 globular clusters. We report on the first tentative identification of RR Lyrae candidates in four globular clusters of the Andromeda galaxy, i.e., G11, G33, G64, and G322. Based on Hubble Space Telescope Wide Field Planetary Camera 2 archive observations…
Cluster PEACE observations of electrons of spacecraft origin
Fazakerley, A. N.; André, M.; Eriksson, A. +6 more
The two PEACE (Plasma Electron And Current Experiment) sensors on board each Cluster spacecraft sample the electron velocity distribution across the full 4<pi> solid angle and the energy range 0.7 eV to 26 keV with a time resolution of 4 s. We present high energy and angular resolution 3D observations of electrons of spacecraft origin in the…
The Infrared Continuum Spectrum of VY Canis Majoris
Decin, Leen; Feuchtgruber, Helmut; Melnick, Gary J. +3 more
We combine spectra of VY CMa obtained with the short- and long-wavelength spectrometers, SWS and LWS, on the Infrared Space Observatory3 to provide a first detailed continuum spectrum of this highly luminous star. The circumstellar dust cloud through which the star is observed is partially self-absorbing, which makes for complex computational mode…
Solar differential rotation determined by tracing coronal bright points in SOHO-EIT images. I. Interactive and automatic methods of data reduction
Vršnak, B.; Wöhl, H.; Clette, F. +3 more
Full-disc solar images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse solar differential rotation determined by tracing coronal bright points. Two different procedures were developed and compared: an interactive and an automatic method. The interactive metho…
The European Large-Area Infrared Space Observatory Survey V: A BeppoSAX Hard X-Ray Survey of the S1 Region
Danese, L.; Alexander, D. M.; Perola, G. C. +18 more
We present BeppoSAX observations of the southern S1 region in the European Large-Area Infrared Space Observatory (ISO) Survey (ELAIS). These observations cover an area of ~1.7 deg2 and reach an on-axis (~0.7 deg2) 2-10 keV (hard X-ray, or HX) sensitivity of ~10-13 ergs s-1 cm-2. This is the fi…
Detection of an X-ray periodicity in the Narrow-line Seyfert 1 Galaxy Mrk 766 with XMM-Newton
Boller, Th.; O'Brien, P. T.; Trümper, J. +3 more
We have analyzed the timing properties of the Narrow-line Seyfert 1 galaxy Mrk 766 observed with XMM-Newton during the PV phase. The source intensity changes by a factor of 1.3 over the 29 000 s observation. If the soft excess is modeled by a black body component, as indicated by the EPIC pn data, the luminosity of the black body component scales …
SwSt 1: an O-rich planetary nebula around a C-rich central star
Crowther, P. A.; Barlow, M. J.; de Koter, A. +2 more
The hydrogen-deficient [WCL] type central star HD 167362 and its planetary nebula (PN) SwSt 1 are investigated. The central star has a carbon-rich emission-line spectrum, and yet the nebula exhibits a 10-µm emission feature from warm silicate dust, perhaps indicating a recent origin for the carbon-rich stellar spectrum. Its stellar and nebul…
Processes associated with particle transport in corotating interaction regions and near stream interfaces
Horbury, T. S.; Forsyth, R. J.; Kunow, H. +5 more
Pioneer and Ulysses observations of energetic particles and solar wind plasma and magnetic fields are analyzed to study particle transport in corotating interaction regions (CIRs) and near stream interfaces (SIs). Energetic particle diffusion with a lowered coefficient near the SIs as compared with the free solar wind may account for the energetic…