Search Publications
The model constraints from the observed trends for the quasi-periodic oscillation in RE J1034+396
Dovčiak, M.; Karas, V.; Czerny, B. +3 more
We analyze the time variability of the X-ray emission of RE J1034+396 - an active galactic nucleus with the first firm detection of a quasi-periodic oscillations (QPO). Based on the results of a wavelet analysis, we find a drift in the QPO central frequency. The change in the QPO frequency correlates with the change in the X-ray flux with a short …
The Rotation Rates of Solar Magnetic Fields During Solar Cycles 21 - 23
Zhang, J.; Li, T.; Chu, Z. +1 more
Employing the synoptic maps of the photospheric magnetic fields from the beginning of solar cycle 21 to the end of 23, we first build up a time - longitude stackplot at each latitude between ±35°. On each stackplot there are many tilted magnetic structures clearly reflecting the rotation rates, and we adopt a cross-correlation technique to explore…
Golden Gravitational Lensing Systems from the Sloan Lens ACS Survey. I. SDSS J1538+5817: One Lens for Two Sources
Grillo, C.; Lombardi, M.; Gobat, R. +4 more
We present a gravitational lensing and photometric study of the exceptional strong lensing system SDSS J1538+5817, identified by the Sloan Lens Advanced Camera for Survey. The lens is a luminous elliptical galaxy at redshift zl = 0.143. Using Hubble Space Telescope public images obtained with two different filters, the presence of two b…
Localization of the X-ray source in the globular cluster G1 with Chandra
Barmby, P.; Heinke, C. O.; Cohn, H. N. +5 more
We report the most accurate X-ray position of the X-ray source in the giant globular cluster G1 in M31 by using the Chandra X-ray Observatory, Hubble Space Telescope (HST) and Canada-France-Hawaii Telescope (CFHT). G1 is clearly detected with Chandra and by cross-registering with HST and CFHT images, we derive a 1σ error radius of 0.15arcsec, sign…
Penetrometry of granular and moist planetary surface materials: Application to the Huygens landing site on Titan
Zarnecki, John C.; Lorenz, Ralph D.; Leese, Mark R. +8 more
The Huygens probe landed on the then unknown surface of Titan in January 2005. A small, protruding penetrometer, part of the Surface Science Package (SSP), was pushed into the surface material measuring the mechanical resistance of the ground as the probe impacted the landing site. We present laboratory penetrometry into room temperature surface a…
Suzaku Observation of the Brightest Broad-line Radio Galaxy 4C 50.55 (IGR J21247+5058)
Isobe, Naoki; Ueda, Yoshihiro; Terashima, Yuichi +4 more
We report the results from a deep Suzaku observation of 4C 50.55 (IGR J21247+5058), the brightest broad-line radio galaxy in the hard X-ray (>10 keV) sky. The simultaneous broadband spectra over 1-60 keV can be represented by a cutoff power law with two layers of absorption and a significant reflection component from cold matter with a solid an…
J004457+4123 (Sharov 21): not a remarkable nova in M 31 but a background quasar with a spectacular UV flare
Pietsch, W.; Hatzidimitriou, D.; Ertel, S. +8 more
Aims: We announce the discovery of a quasar behind the disk of M 31, which was previously classified as a remarkable nova in our neighbour galaxy. It is shown here to be a quasar with a single strong flare where the UV flux has increased by a factor of 20. The present paper is primarily aimed at the remarkable outburst of J004457+4123 (Sharov…
HR 7355 - another rapidly braking He-strong CP star?
Zejda, M.; Paunzen, E.; Henry, G. W. +3 more
Context. Strong meridional mixing induced by rapid rotation is one reason why all hot main-sequence stars are not chemically peculiar. However, the finding that the He-strong CP star HR 7355 is a rapid rotator complicates this concept.
Aims: Our goal is to explain the observed behaviour of HR 7355 based on period analysis of all available pho…
Evidence for Convection in Sunspot Penumbrae
Solanki, S. K.; Bharti, L.; Hirzberger, J.
We present an analysis of twisting motions in penumbral filaments in sunspots located at heliocentric angles from 30° to 48° using three time series of blue continuum images obtained by the Broadband Filter Imager (BFI) on board Hinode. The relations of the twisting motions to the filament brightness and the position within the filament and within…
New seismic analysis of the exoplanet-host star µ Arae
Vauclair, S.; Soriano, M.
Aims: We present detailed modelling of the exoplanet-host star µ Arae, using a new method for the asteroseismic analysis, and taking into account the new value recently derived for the Hipparcos parallax. The aim is to obtain precise parameters for this star and its internal structure, including constraints on the core overshooting.