Search Publications
Multi-scale magnetic field intermittence in the plasma sheet
Balogh, A.; Zhang, T. L.; Klecker, B. +9 more
This paper demonstrates that intermittent magnetic field fluctuations in the plasma sheet exhibit transitory, localized, and multi-scale features. We propose a multifractal-based algorithm, which quantifies intermittence on the basis of the statistical distribution of the strength of burstiness , estimated within a sliding window. Interesting mult…
The radio-mid-infrared correlation and the contribution of 15-µm galaxies to the 1.4-GHz source counts
Pozzi, F.; Calabrese, E.; Gruppioni, C. +5 more
The radio counterparts to the 15-µm sources in the European Large Area ISO Survey southern fields are identified in 1.4-GHz maps down to ~80 µJy. The radio-mid-infrared correlation is investigated and derived for the first time at these flux densities for a sample of this size. Our results show that radio and mid-infrared (MIR) luminos…
A multiwavelength study of the S 106 region. II. Characteristics of the photon dominated region
Schneider, N.; Stutzki, J.; Kramer, C. +3 more
The O star S 106 IR powers a bright, spatially extended 10'x 3' (1.75x 0.5 pc at a distance of 600 pc) photon dominated region (PDR) traced by our observations of FIR fine structure lines and submm molecular transitions. The [C II] 158 mu m, [C I] 609 and 370 mu m, CO 7->6, and CO 4->3 measurements probe the large scale (1.2 pc) PDR emission…
The Age of the Oldest Stars in the Local Galactic Disk from Hipparcos Parallaxes of G and K Subgiants
Sandage, Allan; VandenBerg, Don A.; Lubin, Lori M.
We review the history of the discovery of field subgiant stars, the role that they played in the development of the early understanding of stellar evolution, and their importance in the age dating of the Galactic disk. We use the cataloged data from the Hipparcos satellite in this latter capacity.
Based on Hipparcos parallaxes with relative a…Discovery of a Tight Brown Dwarf Companion to theLow-Mass Star LHS 2397a
Close, Laird M.; Siegler, Nick; Freed, Melanie
Using the adaptive optics system, Hokupa`a, at Gemini North, we have directly imaged a companion around the UKIRT faint standard M8 star LHS 2397a (FS 129) at a separation of 2.96 AU. Near-infrared photometry of the companion has shown it to be an L7.5 brown dwarf and confirmed the spectral type of the primary to be M8. We also derive a substellar…
The X-Ray Spectrum of the Seyfert I Galaxy Markarian 766: Dusty Warm Absorber or Relativistic Emission Lines?
Maraschi, L.; Behar, E.; Page, M. J. +10 more
Competing models for broad spectral features in the soft X-ray spectrum of the Seyfert I galaxy Mrk 766 are tested against data from a 130 ks XMM-Newton observation. A model including relativistically broadened Lyα emission lines of O VIII, N VII, and C VI is a better fit to 0.3-2 keV XMM RGS data than a dusty warm absorber. Moreover, the measured…
The X-ray afterglow of GRB 030329
Ghirlanda, G.; Ghisellini, G.; Tiengo, A. +3 more
We report on XMM and XTE observations of the bright (fluence ~ 10-4 erg cm-2) and nearby (z=0.1685) Gamma-Ray Burst \gr associated to SN2003dh. The first XTE observation, 5 hours after the burst, shows a flux decreasing with time as a power law with index 0.9+/-0.3. Such a decay law is only marginally consistent with a furthe…
A two-component ionized reflection model of MCG-6-30-15
Vaughan, S.; Fabian, A. C.; Ballantyne, D. R.
Ionized reflection has often been considered as the explanation for the unusual Fe Kα variability observed in MCG-6-30-15. In this paper, we test this model using a 325-ks observation of MCG-6-30-15 by XMM-Newton and BeppoSAX. The data are fitted between 2.5 and 80 keV with the constant-density models of Ross & Fabian. The best-fitting ionized…
Soft X-ray emission lines in the afterglow spectrum of GRB 011211: A detailed XMM-Newton analysis
Watson, D.; O'Brien, P. T.; Reeves, J. N. +2 more
We report on an XMM-Newton observation of the X-ray afterglow of the Gamma Ray Burst GRB 011211, originally detected by Beppo-SAX on 11th December 2001. The early afterglow spectrum obtained by XMM-Newton, observed 11 hours after the initial burst, appeared to reveal decaying H-like Kalpha emission lines of Mg, Si, S, Ar and Ca, arising in enriche…
Do bulges of early- and late-type spirals have different morphology?
Peletier, R. F.; Fathi, K.
We study HST/NICMOS H-band images of bulges of two equal-sized samples of early- (TRC3 <= 3) and late-type spiral (mainly Sbc-Sc) galaxies matched in outer disk axis ratio. We find that bulges of late-type spirals are more elongated than their counterparts in early-type spirals. Using a KS-test we find that the two distributions are …