Search Publications
Reconnection Electric Field and Hardness of X-Ray Emission of Solar Flares
Liu, Chang; Wang, Haimin
Magnetic reconnection is believed to be the prime mechanism that triggers solar flares and accelerates electrons up to energies of MeV. In the classical two-dimensional reconnection model, the separation motion of chromospheric ribbons, manifests the successive reconnection that takes place higher up in the corona. Meanwhile, downward traveling en…
Overdensities of Galaxies at z ~ 3.7 in Chandra Deep Field-South
Im, Myungshin; Kang, Eugene
We report the discovery of possible overdensities of galaxies at z ~ 3.7 in Chandra Deep Field-South (CDF-S). These overdensities are identified from a photometric redshift-selected sample and a BVz-selected sample. One overdensity is identified in the proximity of two active galactic nuclei and Lyman break galaxies at z = 3.66 and z = 3.70 at 7σ …
INTEGRAL and XMM-Newton Spectroscopy of GX 339-4 during Hard/Soft Intermediate and High/Soft States in the 2007 Outburst
Mas-Hesse, J. M.; Fabian, A. C.; Miller, J. M. +5 more
We present simultaneous XMM-Newton and International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the luminous black hole transient and relativistic jet source GX 339-4. GX 339-4 started an outburst on 2006 November and our observations were undertaken from 2007 January to March. We triggered five INTEGRAL and three XMM-Newton Targ…
V3885 Sagittarius: A Comparison with a Range of Standard Model Accretion Disks
Szkody, Paula; Sion, Edward M.; Godon, Patrick +3 more
A \widetilde{χ}^2 analysis of standard model accretion disk synthetic spectrum fits to combined Far Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph spectra of V3885 Sagittarius, on an absolute flux basis, selects a model that accurately represents the observed spectral energy distribution. Calculation of the synthetic s…
On the Radial Distribution of Horizontal Branch Stars in NGC 2808
Walker, A. R.; Degl'Innocenti, S.; Zoccali, M. +18 more
We present accurate new ultraviolet and optical BVI photometry for the Galactic globular cluster NGC 2808 based on both ground-based and archival Hubble Space telescope imagery. From this we have selected a sample of ~2000 Horizontal Branch (HB) stars; given the extensive wavelength range considered and the combination of both high angular resolut…
Spectroscopic Signatures of the Superorbital Period in the Neutron Star Binary LMC X-4
Lee, Julia C.; Nowak, Michael A.; Neilsen, Joseph +2 more
We present the first high-resolution X-ray study of emission line variability with superorbital phase in the neutron star binary LMC X-4. Our analysis provides new evidence from X-ray spectroscopy confirming accretion disk precession as the origin of the superorbital period. The spectra, obtained with the Chandra High-Energy Transmission Grating S…
A Collimated, Ionized Bipolar Structure and a High Density Torus in the Planetary Nebula IRAS 17347-3139
de Gregorio-Monsalvo, I.; Anglada, G.; Tafoya, D. +5 more
We present observations of continuum (λ = 0.7, 1.3, 3.6, and 18 cm) and OH maser (λ = 18 cm) emission toward the young planetary nebula IRAS 17347-3139, which is one of the three planetary nebulae that are known to harbor water maser emission. From the continuum observations, we show that the ionized shell of IRAS 17347-3139 consists of two main s…
Galactic Wind in the Nearby Starburst Galaxy NGC 253 Observed with the Kyoto3DII Fabry-Perot Mode
Sugai, H.; Ishigaki, T.; Hattori, T. +5 more
We have observed the central region of the nearby starburst galaxy NGC 253 with the Kyoto Tridimensional Spectrograph II Fabry-Perot mode in order to investigate the properties of its galactic wind. Since this galaxy has a large inclination, it is easy to observe its galactic wind. We produced the Hα, [N II]λ6583, and [S II]λλ6716,6731 images, as …
Probing The Solar Surface: The Oblateness and Astrophysical Consequences
Damiani, C.; Rozelot, J. P.; Pireaux, S.
Based on historical records, the Sun's dimensions are temporally dependent. Until the recent past, varying dimensions were keenly disputed. Recent accurate observations have removed the doubt, whether from direct limb observations or from helioseismology f-modes analysis. A shrinking or an expanding shape is ultimately linked to solar activity, as…
Massive Protoplanetary Disks in Orion Beyond the Trapezium Cluster
Williams, Jonathan P.; Mann, Rita K.
We present Submillimeter Array1The Submillimeter Array is a joint project between the Submillimeter Astrophysical Observatory and the Academica Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academica Sinica. observations of the 880 µm continuum emission from three circumstellar…