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The Thermal Structure of an Active Region Observed Outside the Solar Disk
Landi, E.; Feldman, U.
In the present work we analyze an extensive active region spectrum observed by the SUMER instrument on board SOHO with the aim of determining the thermal structure of the emitting plasma. We found that the plasma is made of three distinct, isothermal components, whose physical properties are similar to coronal hole, quiet-Sun, and active region pl…
IGRJ16479-4514: the first eclipsing supergiant fast X-ray transient?
Campana, S.; Israel, G.; Stella, L. +2 more
Supergiant fast X-ray transients (SFXTs) are a new class of high-mass X-ray binaries recently discovered with INTEGRAL. Hours-long outbursts from these sources have been observed on numerous occasions at luminosities of ~1036-1037ergs-1, whereas their low-level activity at ~1032-1034ergs-…
Evidence of a type 1/type 2 dichotomy in the correlation between quasar optical polarization and host-galaxy/extended emission position angles
Magain, P.; Hutsemékers, D.; Borguet, B. +2 more
Aims:For Seyfert galaxies, the AGN unification model provides a simple and well-established explanation of the type 1/type 2 dichotomy through orientation-based effects. The generalization of this unification model to the higher luminosity AGNs that quasars are remains a key question. The recent detection of type 2 radio-quiet quasars seems to sup…
Spitzer Space Telescope observations of the nucleus of comet 67P/Churyumov-Gerasimenko
Jorda, L.; Lamy, P. L.; Groussin, O. +3 more
Context: Comet 67P/Churyumov-Gerasimenko is the target of the Rosetta mission, and an early characterization of its nucleus is required to assist in preparing the orbital strategy of the spacecraft, the delivery of the Philae surface module and the science operations. We detected the nucleus using the Hubble Space Telescope in March 2003, but had …
The Suzaku Observation of NGC3516: Complex Absorption and the Broad and Narrow FeK Lines
Fabian, Andrew C.; Kunieda, Hideyo; Okajima, Takashi +10 more
We present results from a 150ks Suzaku observation of the Seyfert 1.5 NGC3516 in 2005 October. The source was in a relatively highly absorbed state. Our best-fit model is consistent with the presence of a low-ionization absorber having a column density near 5×1022 cm-2 and covering most of the X-ray continuum source (covering…
Comparative Analysis of Nonthermal Emissions and Electron Transport in a Solar Flare
Yokoyama, T.; Minoshima, T.; Mitani, N.
We study nonthermal emission in a solar flare occurring on 2003 May 29 using RHESSI hard X-ray (HXR) and Nobeyama microwave observations. This flare shows several typical behaviors of HXR and microwave emission: time delay of microwave peaks relative to HXR peaks, loop-top microwave and footpoint HXR sources, and a harder electron energy distribut…
XMM-Newton Observations of the TeV BL Lacertae Object PKS 2155-304 in 2006: Signature of Inverse Compton X-Ray Emission?
Zhang, Y. H.
This paper reports the first discovery of possible inverse Compton (IC) X-ray emission below 10 keV in the typical high-energy peaked BL Lac object (HBL) PKS 2155-304. Two XMM-Newton observations performed in 2006 reveal that the 0.6-10 keV X-ray spectra of the source harden (Δ Γ ~ 0.1-0.3) at break energies of ~4 keV. The concave X-ray spectra of…
On the Origin of Magnetic Helicity in the Solar Corona
Alexander, David; Tian, Lirong
Twenty-three active regions associated with pronounced sigmoidal structure in Yohkoh soft X-ray observations are selected to investigate the origin of magnetic helicity in the solar corona. We calculate the radial magnetic flux of each polarity, the rate of magnetic helicity injection, and total flux of the helicity injection (Δ HLCT) o…
A Jet Associated with the Classical T Tauri Star RY Tauri
Bastien, Pierre; St-Onge, Gilbert
High spatial resolution images have been taken on the Gemini North telescope of the classical T Tauri star RY Tauri. The Hα image, with the continuum properly subtracted, shows a jet extending out to at least 31'' at a position angle of about 295° from the star. A counterjet extending to at least 3.5' in the opposite direction is also visible. The…
Hen 2-104: a close-up look at the Southern Crab
Morisset, C.; Schirmer, M.; Balick, B. +5 more
Aims: The kinematics, shaping, density distribution, expansion distance, and ionized mass of the nebula Hen 2-104, and the nature of its symbiotic Mira are investigated.
Methods: A combination of multi-epoch HST images and VLT integral field high-resolution spectroscopy is used to study the nebular dynamics both along the line of sight and in …