Search Publications
X-Raying the Beating Heart of a Newborn Star: Rotational Modulation of High-energy Radiation from V1647 Ori
Hamaguchi, Kenji; Petre, Robert; Kastner, Joel H. +5 more
We report a periodicity of ~1 day in the highly elevated X-ray emission from the protostar V1647 Ori during its two recent multiple-year outbursts of mass accretion. This periodicity is indicative of protostellar rotation at near-break-up speed. Modeling of the phased X-ray light curve indicates that the high-temperature (~50 MK), X-ray-emitting p…
Toward Identifying the Unassociated Gamma-Ray Source 1FGL J1311.7-3429 with X-Ray and Optical Observations
Cheung, C. C.; Kataoka, J.; Kawai, N. +9 more
We present deep optical and X-ray follow-up observations of the bright unassociated Fermi-LAT gamma-ray source 1FGL J1311.7-3429. The source was already known as an unidentified EGRET source (3EG J1314-3431, EGR J1314-3417), hence its nature has remained uncertain for the past two decades. For the putative counterpart, we detected a quasi-sinusoid…
Discovery of a Significant Magnetic Cataclysmic Variable Population in the Limiting Window
van den Berg, Maureen; Grindlay, Jonathan E.; Servillat, Mathieu +2 more
We have discovered 10 periodic X-ray sources from the 1 Ms Chandra ACIS observation of the Limiting Window (LW), a low-extinction region (AV ~ 3.9) at 1fdg4 south of the Galactic center. The observed periods (~1.3-3.4 hr) and the X-ray luminosities (1031.8-32.9 erg s-1 at 8 kpc) of the 10 periodic sources, combined…
X-Ray Binaries in the Ultrahigh Encounter Rate Globular Cluster NGC 6388
Heinke, Craig O.; Bailyn, Charles D.; Cohn, Haldan N. +5 more
We report the results of a joint Chandra Hubble Space Telescope study of the X-ray binary (XRB) population in the massive, high-density globular cluster NGC 6388. NGC 6388 has one of the highest predicted XRB production rates of any Galactic cluster. We detected a large population of 61 Chandra sources within the half-mass radius with LX
Multiscale Dynamics of Solar Magnetic Structures
Davila, Joseph M.; Uritsky, Vadim M.
Multiscale topological complexity of the solar magnetic field is among the primary factors controlling energy release in the corona, including associated processes in the photospheric and chromospheric boundaries. We present a new approach for analyzing multiscale behavior of the photospheric magnetic flux underlying these dynamics as depicted by …
Determination of Prominence Plasma β from the Dynamics of Rising Plumes
Tripathi, Durgesh; Hillier, Andrew; Hillier, Richard
Observations by the Hinode satellite show in great detail the dynamics of rising plumes, dark in chromospheric lines, in quiescent prominences that propagate from large (~10 Mm) bubbles that form at the base of the prominences. These plumes present a very interesting opportunity to study magnetohydrodynamic (MHD) phenomena in quiescent prominences…
Chandra Observations of Five INTEGRAL Sources: New X-Ray Positions for IGR J16393-4643 and IGR J17091-3624
Rahoui, F.; Tomsick, J. A.; Rodriguez, J. +1 more
The Chandra High Resolution Camera observed the fields of five hard X-ray sources in order to help us obtain X-ray coordinates with subarcsecond precision. These observations provide the most accurate X-ray positions known for IGR J16393-4643 and IGR J17091-3624. The obscured X-ray pulsar IGR J16393-4643 lies at R.A. (J2000) = 16h39
Sizes, Half-mass Densities, and Mass Functions of Star Clusters in the Merger Remnant NGC 1316: Clues to the Fate of Second-generation Globular Clusters
Goudfrooij, Paul
We study mass functions of globular clusters derived from Hubble Space Telescope/Advanced Camera for Surveys images of the early-type merger remnant galaxy NGC 1316, which hosts a significant population of metal-rich globular clusters of intermediate age (~3 Gyr). For the old, metal-poor ("blue") clusters, the peak mass of the mass function {\cal …
Sound-speed Inversion of the Sun Using a Nonlocal Statistical Convection Theory
Deng, Licai; Christensen-Dalsgaard, Jørgen; Zhang, Chunguang +1 more
Helioseismic inversions reveal a major discrepancy in sound speed between the Sun and the standard solar model just below the base of the solar convection zone. We demonstrate that this discrepancy is caused by the inherent shortcomings of the local mixing-length theory adopted in the standard solar model. Using a self-consistent nonlocal convecti…
Possible Detection of an Emission Cyclotron Resonance Scattering Feature from the Accretion-powered Pulsar 4U 1626-67
Mihara, T.; Tashiro, M. S.; Yamada, S. +7 more
We present analysis of 4U 1626-67, a 7.7 s pulsar in a low-mass X-ray binary system, observed with the hard X-ray detector of the Japanese X-ray satellite Suzaku in 2006 March for a net exposure of ~88 ks. The source was detected at an average 10-60 keV flux of ~4 × 10-10 erg cm-2 s-1. The phase-averaged spectrum i…