Search Publications
Large-scale Magnetic Helicity Fluxes Estimated from MDI Magnetic Synoptic Charts over the Solar Cycle 23
Zhang, Hongqi; Yang, Shangbin
To investigate the characteristics of large-scale and long-term evolution of magnetic helicity with solar cycles, we use the method of Local Correlation Tracking to estimate the magnetic helicity evolution over solar cycle 23 from 1996 to 2009 using 795 MDI magnetic synoptic charts. The main results are as follows: the hemispheric helicity rule st…
Hard X-Ray and Ultraviolet Observations of the 2005 January 15 Two-ribbon Flare
Qiu, J.; Cheng, J. X.; Kerr, G.
It is well known that two-ribbon flares observed in Hα and ultraviolet (UV) wavelengths mostly exhibit compact and localized hard X-ray (HXR) sources. In this paper, we present comprehensive analysis of a two-ribbon flare observed in UV 1600 Å by Transition Region and Coronal Explorer and in HXRs by Reuven Ramaty High Energy Solar Spectroscopic Im…
Suzaku Observations of the Non-thermal Supernova Remnant HESS J1731-347
Acero, Fabio; Klochkov, Dmitry; Bamba, Aya +7 more
A detailed analysis of the non-thermal X-ray emission from the northwestern and southern parts of the supernova remnant (SNR) HESS J1731-347 with Suzaku is presented. The shell portions covered by the observations emit hard and lineless X-rays. The spectrum can be reproduced by a simple absorbed power-law model with a photon index Γ of 1.8-2.7 and…
Spin-down Measurement of PSR J1813-1749: The Energetic Pulsar Powering HESS J1813-178
Camilo, F.; Gotthelf, E. V.; Halpern, J. P.
Two new X-ray timing observations of the 44.7 ms pulsar in G12.82-0.02/HESS J1813-178 were obtained with Chandra and XMM-Newton to determine its precise spin-down rate. With a period derivative of \dot{P} = 1.265\times 10^{-13}, PSR J1813-1749 is the third most energetic pulsar in the Galaxy, having spin-down luminosity \dot{E} = 5.6\times 10^{37}…
Herschel PACS Observations and Modeling of Debris Disks in the Tucana-Horologium Association
Ménard, F.; Dent, W. R. F.; Krivov, A. V. +9 more
We present Herschel PACS photometry of 17 B- to M-type stars in the 30 Myr old Tucana-Horologium Association. This work is part of the Herschel Open Time Key Programme "Gas in Protoplanetary Systems". 6 of the 17 targets were found to have infrared excesses significantly greater than the expected stellar IR fluxes, including a previously unknown d…
A Refined QSO Selection Method Using Diagnostics Tests: 663 QSO Candidates in the Large Magellanic Cloud
Trichas, Markos; Alcock, Charles; Rowan-Robinson, Michael +4 more
We present 663 QSO candidates in the Large Magellanic Cloud (LMC) selected using multiple diagnostics. We started with a set of 2566 QSO candidates selected using the methodology presented in our previous work based on time variability of the MACHO LMC light curves. We then obtained additional information for the candidates by crossmatching them w…
The Nature of the UV/Optical Emission of the Ultraluminous X-Ray Source in Holmberg II
Tao, Lian; Feng, Hua; Grisé, Fabien +1 more
We report on UV and X-ray spectroscopy and broadband optical observations of the ultraluminous X-ray source in Holmberg II. Fitting various stellar spectral models to the combined, non-simultaneous data set, we find that normal metallicity stellar spectra are ruled out by the data, while low-metallicity, Z = 0.1 Z ⊙, late O-star spectra…
The HST/ACS Coma Cluster Survey. VIII. Barred Disk Galaxies in the Core of the Coma Cluster
Ferguson, Henry C.; Mobasher, Bahram; Balcells, Marc +16 more
We use high-resolution (~0farcs1) F814W Advanced Camera for Surveys (ACS) images from the Hubble Space Telescope ACS Treasury survey of the Coma cluster at z ~ 0.02 to study bars in massive disk galaxies (S0s), as well as low-mass dwarf galaxies in the core of the Coma cluster, the densest environment in the nearby universe. Our study helps to con…
Discovery of Crystallized Water Ice in a Silhouette Disk in the M43 Region
Tokunaga, Alan T.; Terada, Hiroshi
We present the 1.9-4.2 µm spectra of the five bright (L <= 11.2) young stars associated with silhouette disks with a moderate to high inclination angle of 39°-80° in the M42 and M43 regions. The water ice absorption is seen toward d121-1925 and d216-0939, while the spectra of d182-316, d183-405, and d218-354 show no water ice feature arou…
Titan's Transport-driven Methane Cycle
Mitchell, Jonathan L.
The mechanisms behind the occurrence of large cloud outbursts and precipitation on Titan have been disputed. A global- and annual-mean estimate of surface fluxes indicated only 1% of the insolation, or ~0.04 W m-2, is exchanged as sensible and/or latent fluxes. Since these fluxes are responsible for driving atmospheric convection, it ha…