Search Publications
The XMM-NEWTON Ω project. I. The X-ray luminosity-temperature relation at z>0.4
Bartlett, J. G.; Giard, M.; Nichol, R. C. +9 more
We describe XMM-Newton Guaranteed Time observations of a sample of eight high redshift (0.45<z<0.62) clusters. The goal of these observations was to measure the luminosity and the temperature of the clusters to a precision of ∼10%, leading to constraints on the possible evolution of the luminosity-temperature (Lx-Tx) re…
Key parameters of W UMa-type contact binaries discovered by HIPPARCOS
Selam, S. O.
A sample of W UMa-type binaries which were discovered by the HIPPARCOS satellite was constructed with the aid of well defined selection criteria described in this work. The selection process showed up that several systems of which the variability types have been assigned as EB in HIPPARCOS catalogue are genuine contact binaries of W UMa-type. The …
Helicity of magnetic clouds and their associated active regions
Pevtsov, Alexei A.; Leamon, Robert J.; Canfield, Richard C. +3 more
In this work we relate the magnetic and topological parameters of twelve interplanetary magnetic clouds to associated solar active regions. We use a cylindrically symmetric constant-α force-free model to derive field line twist, total current, and total magnetic flux from in situ observations of magnetic clouds. We compare these properties with th…
Rings in the haloes of planetary nebulae
Corradi, R. L. M.; Sánchez-Blázquez, P.; Mellema, G. +2 more
We present a search for rings or arcs in the haloes of planetary nebulae (PNe). We discovered such structures in eight PNe, tripling the sample of PNe with known rings. This shows that, contrary to what was believed to date, the occurrence of mass loss fluctuations with timescales of 102-103 yrs at the end of the asymptotic g…
The Ultraluminous X-Ray Source NGC 1313 X-2 (MS 0317.7-6647) and Its Environment
Kaaret, Philip; Turolla, Roberto; Zampieri, Luca +5 more
We present new optical and Chandra observations of the field containing the ultraluminous X-ray source NGC 1313 X-2. On an ESO 3.6 m image, the Chandra error box embraces an R=21.6 pointlike object and excludes a previously proposed optical counterpart. The resulting X-ray/optical flux ratio of NGC 1313 X-2 is ~500. The value of fX/f
Helioseismology of Time-Varying Flows Through The Solar Cycle
Gizon, Laurent
Flows in the upper convection zone are measured by helioseismology on a wide variety of scales. These include differential rotation and meridional circulation, local flows around complexes of magnetic activity and sunspots, and convective flows. The temporal evolution of flows through cycle 23 reveals connections between mass motions in the solar …
Radio, optical and infrared observations of CLASS B0128+437
McKean, J. P.; Biggs, A. D.; Browne, I. W. A. +4 more
We present new observations of the gravitational lens system CLASS B0128+437 made in the optical, infrared and radio regimes. Hubble Space Telescope observations detect only a very faint, extended object in the I band with no obvious emission from the lensed images visible; no detection at all is made in the V band. The lens system is detected wit…
Similarities and Differences between Coronal Holes and the Quiet Sun: Are Loop Statistics the Key?
Solanki, S. K.; Wiegelmann, T.
Coronal holes (CH) emit significantly less at coronal temperatures than quiet-Sun regions (QS), but can hardly be distinguished in most chromospheric and lower transition region lines. A key quantity for the understanding of this phenomenon is the magnetic field. We use data from SOHO/MDI to reconstruct the magnetic field in coronal holes and the …
Evidence of Rapid Flux Emergence Associated with the M8.7 Flare on 2002 July 26
Qiu, Jiong; Jing, Ju; Wang, Haimin +5 more
In this paper, we present a detailed study of the M8.7 flare that occurred on 2002 July 26 using data from the Big Bear Solar Observatory (BBSO), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), the Transition Region and Coronal Explorer (TRACE), and the Solar and Heliospheric Observatory (SOHO). This flare has interesting properties simila…
Two-dimensional spectroscopy of a sunspot. I. Properties of the penumbral fine structure
Bellot Rubio, L. R.; Schlichenmaier, R.; Tritschler, A. +3 more
We investigate the properties of the fine structure of a sunspot penumbra based on spectroscopic measurements with high spectral (λ/δλ=250 000) and high spatial (≈0.5 arcsec) resolution. The magnetically insensitive Fe I 557.6 nm line is used to probe the penumbral atmosphere. The data was taken at the German Vacuum Tower Telescope with the 2D-spe…