Search Publications
X-Rays from the Globular Cluster G1: Intermediate-Mass Black Hole or Low-Mass X-Ray Binary?
Pooley, David; Rappaport, Saul
The globular cluster G1 (Mayall II) in M31 is the most massive (~107 Msolar) stellar cluster in the Local Group, and it has the highest central velocity dispersion (~28 km s-1). It has been claimed to host a central ~20,000 Msolar black hole, but these claims have been controversial. We investigate here …
Spectral-timing evidence for a very high state in the narrow-line Seyfert 1 Ark 564
Papadakis, I. E.; Uttley, P.; Arévalo, P. +2 more
We use a 100ks long XMM-Newton observation of the narrow-line Seyfert 1 galaxy Ark 564 and combine it with the month-long monitoring of the same source produced by ASCA, to calculate the phase lags and coherence between different energy bands, over frequencies from ~10-6 to 10-3Hz. This is the widest frequency range for which…
Hydrostatic Modeling of the Integrated Soft X-Ray and Extreme Ultraviolet Emission in Solar Active Regions
Winebarger, Amy R.; Warren, Harry P.
Many studies of the solar corona have shown that the observed X-ray luminosity is well correlated with the total unsigned magnetic flux. In this paper we present results from the extensive numerical modeling of active regions observed with the Solar and Heliospheric Observatory (SOHO) EUV Imaging Telescope (EIT), the Yohkoh Soft X-Ray Telescope (S…
A global circulation model of Saturn's thermosphere
Yelle, R. V.; Müller-Wodarg, I. C. F.; Aylward, A. D. +1 more
We present the first 3-dimensional self-consistent calculations of the response of Saturn's global thermosphere to different sources of external heating, giving local time and latitudinal changes of temperatures, winds and composition at equinox and solstice. Our calculations confirm the well-known finding that solar EUV heating alone is insuffici…
High-Resolution Observations of Multiwavelength Emissions during Two X-Class White-Light Flares
Xu, Yan; Cao, Wenda; Liu, Chang +5 more
We observed two X-class white-light flares (WLFs) on 2003 October 29 (~20:40 UT) and November 2 (~17:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76 cm aperture, and the cadence was as high as 2 s. This is the …
Mid infrared properties of distant infrared luminous galaxies
Elbaz, D.; Morrison, G.; Dickinson, M. +3 more
We present evidence that the mid infrared (MIR, rest frame 5-30 µm) is a good tracer of the total infrared luminosity, L(IR)(=L[8{-}1000 µm]), and star formation rate (SFR), of galaxies up to z∼ 1.3. We use deep MIR images from the Infrared Space Observatory (ISO) and the Spitzer Space Telescope in the Northern field of the Great Obser…
The auroral and ionospheric flow signatures of dual lobe reconnection
Milan, S. E.; Imber, S. M.; Hubert, B.
We present the first substantial evidence for the occurrence of dual lobe reconnection from ionospheric flows and auroral signatures. The process of dual lobe reconnection refers to an interplanetary magnetic field line reconnecting with lobe field lines in both the northern and southern hemispheres. Two bursts of sunward plasma flow across the no…
Accretion and Nuclear Activity of Quiescent Supermassive Black Holes. I. X-Ray Study
Elvis, M.; Graham, Alister W.; Pellegrini, S. +5 more
We have studied the nuclear activity in a sample of six quiescent early-type galaxies, with new Chandra data and archival HST optical images. Their nuclear sources have X-ray luminosities ~1038-1039 ergs s-1 (LX/LEdd~10-8 to 10-7) and colors or spectra consistent with acc…
Effect of adiabatic cooling on the fitted parallel mean free path of solar energetic particles
Zhang, M.; Qin, G.; Dwyer, J. R.
The focused transport equation without adiabatic energy loss is widely used to model solar energetic particles' (SEP) interplanetary propagation by fitting spacecraft data. We incorporate the adiabatic energy loss effect, provided by the divergence of the solar wind flows, into the focused transport equation. The equation is then solved numericall…
The radio to TeV orbital variability of the microquasar LS I +61 303
Paredes, J. M.; Romero, G. E.; Ribó, M. +1 more
Context: .The microquasar LS I +61 303 has recently been detected at TeV energies by the Cherenkov telescope MAGIC, presenting variability on timescales similar to its orbital period. This system has been intensively observed at different wavelengths during the last three decades, showing a very complex behavior along the orbit.
Aims: .We aim …