Search Publications

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data

Santos-Lleó, M.; Krongold, Y.; Rodríguez-Pascual, P. +3 more

Aims: The detailed analysis of all data taken by the XMM-Newton satellite of UGC 11763 to characterize the different components that are emitting and absorbing radiation in the vicinity of the active nucleus.
Methods: The continuum emission was studied through the EPIC spectra taking profit of the spectral range of these cameras. The high reso…

Direct measurement of the formation height difference of the 630 nm Fe I solar lines

Faurobert, M.; Uitenbroek, H.; Ricort, G. +4 more

Context: Spectral lines formed over a limited height range in either a stellar or planetary atmosphere provide us with information about the physical conditions within this height range. In this context, an important quantity is the so-called line formation depth. It is usually determined from numerical calculation of the atmospheric opacity in th…

On oscillations found in an active region with EIS on Hinode

Doyle, J. G.; O'Shea, E.

Aims: Using temporal series (40'' slot) data in the ion{Fe}{xii} 195 Å line from the extreme-ultraviolet imaging spectrometer (EIS) on board the Hinode satellite, we seek to carry out a statistical study of oscillations in an active region.
Methods: Using wavelet techniques, we measure the frequency and duration of oscillations found in the ti…

The Crab pulsar and its pulsar-wind nebula in the optical and infrared

Lundqvist, P.; Tziamtzis, A.; Djupvik, A. A.

Aims. We investigate the emission mechanism and evolution of pulsars that are associated with supernova remnants.
Methods: We used imaging techniques in both the optical and near infrared, using images with very good seeing (≤0.^primeprime6) to study the immediate surroundings of the Crab pulsar. In the case of the infrared, we took …

SN 1999ga: a low-luminosity linear type II supernova?

Smartt, S. J.; Altavilla, G.; Turatto, M. +11 more

Context: Type II-linear supernovae are thought to arise from progenitors that have lost most of their H envelope by the time of the explosion, and they are poorly understood because they are only occasionally discovered. It is possible that they are intrinsically rare, but selection effects due to their rapid luminosity evolution may also play an …

Magnetic evolution of superactive regions. Complexity and potentially unstable magnetic discontinuities

Romano, P.; Zuccarello, F.; Giorgi, F. +1 more

Context: It is widely accepted that solar flares are manifestations of magnetic reconnection events taking place in the solar atmosphere. Several aspects of these events remain unclear, although many efforts have been devoted to the investigation of magnetic field configurations at flare occurrence sites.
Aims: In this work, we have studied th…

X-ray emission from the M9 dwarf 1RXS J115928.5-524717. Quasi-quiescent coronal activity at the end of the main-sequence

Schmitt, J. H. M. M.; Robrade, J.

Aims: X-ray emission is an important diagnostic for studying magnetic activity in presumably fully convective, very low-mass stars with virtually neutral photospheres.
Methods: We analyse an XMM-Newton observation of 1RXS J115928.5-524717, an ultracool dwarf with spectral type M9, and compare its X-ray properties to those of other similar very…

The Hipparcos catalog. Commentary on: Perryman M. A. C., Lindegren L., Kovalevsky J., et al., 1997, A&A, 323, L49

van Leeuwen, F.

On the origin of reverse polarity patches found by Hinode in sunspot penumbrae

Ichimoto, K.; Sánchez Almeida, J.

Context: The topology of penumbral magnetic fields is poorly known. The satellite Hinode has recently revealed penumbral structures of a magnetic polarity that is opposite to the main sunspot polarity. They may be direct confirmation that magnetic field lines and mass flows return to the solar interior throughout the penumbra, a configuration prev…

Radial distribution of near-UV flux in disc galaxies in the range 0 ⪉ z ⪉ 1

Beckman, J. E.; Trujillo, I.; Azzollini, R.

Context: In the last 8 Gyr of cosmic time the global star formation rate (SFR) has declined by roughly an order of magnitude, and most of this activity has been progressively confined to ever less massive galaxies (“downsizing”). Previous studies show that the main drivers of the decline in the global SFR are the spiral galaxies. However, we still…