Search Publications
The Hard X-Ray Continuum of Cen A Observed With INTEGRAL SPI
Jourdain, Elisabeth; Roques, Jean-Pierre; Evans, Daniel A. +1 more
We revisit the average hard X-ray spectrum from the active galactic nucleus (AGN) of Centaurus A (Cen A) using 10 yr worth of observations with INTEGRAL SPI. This source has the highest flux observed from any AGNs in the SPI bandpass (23 keV-8 MeV). The 10 year light curve of Cen A is presented, and hardness ratios confirm that the spectral shape …
Separable Solutions of Force-Free Spheres and Applications to Solar Active Regions
Mangalam, A.; Ravindra, B.; Prasad, A.
We present a systematic study of the force-free field equation for simple axisymmetric configurations in spherical geometry and apply it to the solar active regions. The condition of separability of solutions in the radial and angular variables leads to two classes of solutions: linear and nonlinear force-free fields (NLFF). We have studied these …
Hubble Space Telescope Far Ultraviolet Spectroscopy of the Recurrent Nova T Pyxidis
Williams, Robert E.; Livio, Mario; Woodward, Charles E. +5 more
With six recorded nova outbursts, the prototypical recurrent nova T Pyxidis (T Pyx) is the ideal cataclysmic variable system to assess the net change of the white dwarf mass within a nova cycle. Recent estimates of the mass ejected in the 2011 outburst ranged from a few ~10-5 M ⊙ to 3.3 × 10-4 M ⊙, and a…
Hard X-Ray Emission and 44Ti Line Features of the Tycho Supernova Remnant
Wang, Wei; Li, Zhuo
A deep hard X-ray survey of the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellite has detected for the first time non-thermal emission up to 90 keV in the Tycho supernova (SN) remnant. Its 3-100 keV spectrum is fitted with a thermal bremsstrahlung of kT ~ 0.81 ± 0.45 keV plus a power-law model of Γ ~ 3.01 ± 0.16. Based on diffus…
A Combined Study of Photospheric Magnetic and Current Helicities and Subsurface Kinetic Helicities of Solar Active Regions during 2006-2013
Komm, R.; Petrie, G. J. D.; Seligman, D.
We compare the average photospheric current helicity Hc , photospheric twist parameter α (a well-known proxy for the full relative magnetic helicity), and subsurface kinetic helicity Hk for 194 active regions observed between 2006-2013. We use 2440 Hinode photospheric vector magnetograms, and the corresponding subsurface flui…
Entropy Flattening, Gas Clumping, and Turbulence in Galaxy Clusters
Lapi, A.; Fusco-Femiano, R.
Several physical processes and formation events are expected in cluster outskirts, a vast region up to now essentially not covered by observations. The recent Suzaku (X-ray) and Planck (Sunyaev-Zel'dovich (SZ) effect) observations out to the virial radius have highlighted in these peripheral regions a rather sharp decline of the intracluster gas t…
Emission Measure Distribution for Diffuse Regions in Solar Active Regions
Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A. +1 more
Our knowledge of the diffuse emission that encompasses active regions is very limited. In this paper we investigate two off-limb active regions, namely, AR 10939 and AR 10961, to probe the underlying heating mechanisms. For this purpose, we have used spectral observations from Hinode/EIS and employed the emission measure (EM) technique to obtain t…
CLASH: Extending Galaxy Strong Lensing to Small Physical Scales with Distant Sources Highly Magnified by Galaxy Cluster Members
Infante, L.; Zheng, W.; Molino, A. +35 more
We present a complex strong lensing system in which a double source is imaged five times by two early-type galaxies. We take advantage in this target of the extraordinary multi-band photometric data set obtained as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) program, complemented by the spectroscopic measurements of the VL…
Circumnuclear Molecular Gas in Megamaser Disk Galaxies NGC 4388 and NGC 1194
Greene, Jenny E.; van de Ven, Glenn; Seth, Anil +3 more
We explore the warm molecular and ionized gas in the centers of two megamaser disk galaxies using K-band spectroscopy. Our ultimate goal is to determine how gas is funneled onto the accretion disk, here traced by megamaser spots on sub-parsec scales. We present NIR IFU data with a resolution of ~50 pc for two galaxies: NGC 4388 with VLT/SINFONI an…
ALMA Observations of the Host Galaxy of GRB 090423 at z = 8.23: Deep Limits on Obscured Star Formation 630 Million Years after the Big Bang
Berger, E.; Chary, R. -R.; Chornock, R. +7 more
We present rest-frame far-infrared (FIR) and optical observations of the host galaxy of GRB 090423 at z = 8.23 from the Atacama Large Millimeter Array (ALMA) and the Spitzer Space Telescope, respectively. The host remains undetected to 3σ limits of F ν(222 GHz) <~ 33 µJy and F ν(3.6 µm) <~ 81 nJy. The FIR li…