Search Publications
Inferring Small-Scale Flatfields from Solar Rotation
Schou, J.; Wachter, R.
We present a method to infer small-scale flatfields for imaging solar instruments using only regular-observation intensity images with a fixed field of view. The method is related to the flatfielding method developed by Kuhn, Lin, and Loranz (Publ. Astron. Soc. Pac. 103, 1097 - 1108, 1991), but does not require image offsets. Instead, it takes adv…
The chromospherically active binary CFTuc revisited
Erdem, A.; Zola, S.; Doǧru, D. +1 more
This paper presents results derived from analysis of new spectroscopic and photometric observations of the chromospherically active binary system CFTuc. New high-resolution spectra, taken at the Mt. John University Observatory in 2007, were analysed using two methods: cross-correlation and Fourier-based disentangling. As a result, new radial veloc…
Can magnetotail reconnection produce the auroral intensities observed in the conjugate ionosphere?
Snekvik, K.; Østgaard, N.; Haaland, S. E. +5 more
In a recent case study, Borg et al. (2007) reported that an inverted V structure, caused by a field-aligned potential drop of 30 kV producing very strong X-ray aurora, was found in connection with tail reconnection. However, the in situ particle measurements indicated clearly that the particles responsible for the X-ray aurora were not accelerated…
The Impact of Geometry on Observations of CME Brightness and Propagation
Webb, D. F.; Howard, R. A.; Vourlidas, A. +2 more
Coronal mass ejections (CMEs) have a significant impact on space weather and geomagnetic storms and so have been the subject of numerous studies. Most CME observations have been made while these events are near the Sun (e.g., SOHO/LASCO). Recent data from the Coriolis/SMEI and STEREO/SECCHI-HI instruments have imaged CMEs farther into the heliosph…
Interpreting Helioseismic Structure Inversion Results of Solar Active Regions
Basu, Sarbani; Li, Linghuai; Lin, Chia-Hsien
Helioseismic techniques such as ring-diagram analysis have often been used to determine the subsurface structural differences between solar active and quiet regions. Results obtained by inverting the frequency differences between the regions are usually interpreted as the sound-speed differences between them. These in turn are used as a measure of…
The very short supersoft X-ray state of the classical nova M31N 2007-11a
Della Valle, M.; Pietsch, W.; Haberl, F. +9 more
Context: Short supersoft X-ray source (SSS) states (durations ≤100 days) of classical novae (CNe) indicate massive white dwarfs that are candidate progenitors of supernovae type Ia.
Aims: We carry out a dedicated optical and X-ray monitoring program of CNe in the bulge of M 31.
Methods: We discovered M31N 2007-11a and determined its optica…
Exploring the spreading layer of GX 9+9 using RXTE and INTEGRAL
Hakala, P.; Paizis, A.; Vilhu, O. +3 more
We have fitted ~200 RXTE and INTEGRAL spectra of the neutron star (NS) low-mass X-ray binary (LMXB) GX 9+9 from 2002 to 2007 with a model consisting of a disc blackbody and another blackbody representing the spreading layer (SL), i.e. an extended accretion zone on the NS surface as opposed to the more traditional disc-like boundary layer. Contrary…
Ethane aerosol phase evolution in Titan's atmosphere
Dartois, Emmanuel; Bauerecker, Sigurd
Strong experimental evidence is presented that the northern polar cloud observed in Titan's atmosphere by the Cassini orbiter (VIMS) was indeed composed of ethane aerosol as proposed by Griffith et al. [2006. Science 313, 1620-1622]. We report on the condensation and phase behavior of ethane aerosol under atmospheric conditions of Titan (145 hPa, …
On the Anticorrelation Between Galaxy Light Concentration and X-ray-to-Optical Flux Ratio
Cepa, J.; Bongiovanni, A.; Pérez García, A. M. +6 more
Active galactic nuclei (AGNs) play an important role in many aspects of modern cosmology, and of particular interest is the issue of the interplay between AGNs and their host galaxy. Using X-ray and optical data sets, we have explored the properties of a large sample of AGNs in the Subaru/XMM-Newton Deep Survey field, and studied their evolution i…
The evolution of cluster early-type galaxies over the past 8 Gyr
Fritz, A.; Jørgensen, I.; Schiavon, R. P. +1 more
We present the Fundamental Plane (FP) of early-type galaxies in the clusters of galaxies RXJ1415.1+3612 at z=1.013. This is the first detailed FP investigation of cluster early-type galaxies at redshift z=1. The distant cluster galaxies follow a steeper FP relation compared to the local FP. The change in the slope of the FP can be interpreted as a…