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Research Interests: Physics, Star Formation, Astrophysics, Astronomy, Gamma Ray Burst, and 5 moreBlack Hole, Sky, Gamma Ray, Supernova, and Telescope
We report MMT Echelle radial velocity observations of 52 giants within 3 core radii of the center of NGC 6712. The mean radial velocity of these stars is −107.5 km/s, with a line of sight velocity dispersion of 4.0 km/s. We use these... more
We report MMT Echelle radial velocity observations of 52 giants within 3 core radii of the center of NGC 6712. The mean radial velocity of these stars is −107.5 km/s, with a line of sight velocity dispersion of 4.0 km/s. We use these data, together with CCD photometry of the cluster, to derive a mass to light ratio for the center of the cluster of 0.7, an unusually low value.
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The development of a survey that exploits the event-by-event data capture ca-pabilities of the Swift-BAT during periods of spacecraft slewing is instrumental in expanding the overall capabilities of the Swift mission by expanding its... more
The development of a survey that exploits the event-by-event data capture ca-pabilities of the Swift-BAT during periods of spacecraft slewing is instrumental in expanding the overall capabilities of the Swift mission by expanding its spa-tial and time coverage without affecting any of its conventional pointing-mode operations. We hereby demonstrate both the importance and the feasibility of a BAT Slew Survey (BATSS), by first showing that the imaging method em-ployed not only extends coverage but also deepens the instrument sensitivity when compared to pointing observations of equivalent source exposure time and coding fraction. An imaging and detection algorithm for slew-mode data has been devised and implemented for real-time data taking, and the automated pipeline has been shown to handle the required data rates and is capable of reporting positions of candidate GRBs in as short as 2.5 hours for the fastest speeds of spacecraft telemetry downlink. The BATSS system is also equippe...
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KU Cygni is an Algol-type eclipsing binary consisted of a F-type main sequence star (gainer) with a large accretion disk, and a K5III red giant (donor). Here we present the discovery of an 8-yr dimming begining in 1895 found from its 100... more
KU Cygni is an Algol-type eclipsing binary consisted of a F-type main sequence star (gainer) with a large accretion disk, and a K5III red giant (donor). Here we present the discovery of an 8-yr dimming begining in 1895 found from its 100 yr DASCH light curve. It showed a 0.7 mag slow dimming from 1895 to 1903, and then quickly
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We present initial HST results of our deep (100 ks), simultaneous Chandra/HST observations of two low-extinction "windows" in the Galactic Bulge: Baade's Window (Av=1.3) and Stanek's Window (Av=2.8). These fields offer a... more
We present initial HST results of our deep (100 ks), simultaneous Chandra/HST observations of two low-extinction "windows" in the Galactic Bulge: Baade's Window (Av=1.3) and Stanek's Window (Av=2.8). These fields offer a unique opportunity to look for low-luminosity X-ray sources at only a few degrees ( 4 and 2 degr) from the Galactic Center. As part of the ongoing Chandra
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BJ Wilkes, P. Green, R. Brissenden, R. Cameron, A. Dobrzycki, J. Drake, N. Evans, A. Fruscione, T. Gaetz, M. Garcia, H. Ghosh, J. Grimes, J. Grindlay, E. Hooper, M. Karovska, V. Kashyap, D.-W. Kim, K. Kowal, H. Marshall, A. Mossman, D.... more
BJ Wilkes, P. Green, R. Brissenden, R. Cameron, A. Dobrzycki, J. Drake, N. Evans, A. Fruscione, T. Gaetz, M. Garcia, H. Ghosh, J. Grimes, J. Grindlay, E. Hooper, M. Karovska, V. Kashyap, D.-W. Kim, K. Kowal, H. Marshall, A. Mossman, D. Morris, J. Nichols, A. ...
Research Interests: History, Geology, Physics, X Ray Astronomy, Data Analysis, and 15 moreActive Galactic Nuclei, Optical Spectroscopy, Astrophysics, Optical Imaging, Astronomy, X Rays, High Redshift Universe, Luminosity, Observatory, Luminosity function, Spatial resolution, Sky, Astronomy and Astrophysics, Redshift, and Chandra X-ray Observatory
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ABSTRACT The X-ray burster 1E1724-3045, located in the globular cluster Terzan 2 was observed on November 1996 for 100 ksec with the PCA and HEXTE experiments aboard the Rossi X-ray Timing Explorer. During the observation, the PCA count... more
ABSTRACT The X-ray burster 1E1724-3045, located in the globular cluster Terzan 2 was observed on November 1996 for 100 ksec with the PCA and HEXTE experiments aboard the Rossi X-ray Timing Explorer. During the observation, the PCA count rate was about 470 cts/s in the 2-20 keV range (background substracted). We have characterized the aperiodic variability of the source over a wide frequency band (2 10-3-40 Hz). The 2-20 keV emission of this source shows a light level of noise variability (RMS ~25%). The Fourier spectrum can be modelled in terms of the shot noise model with two characteristic lifetimes of 670 and 16 msec although a continuous distribution of shots lifetimes can not be excluded. These two components account for about the same contribution to the total RMS of the source (~10%). In addition to these components, a broad and asymetric peaked noise feature, located at 0.8 Hz, appears in the spectrum. This QPO-like feature accounts for a ~5% of the RMS. Both the lifetimes of the shots and the QPO frequency seems independent on the energy but the integrated RMS of all three components increases between the 2-5 keV and 5-20 keV range. We show that 1E1724-3045 has striking timing similarities with the black hole candidate GRO J0422+32 (Nova Persei 1992).
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ABSTRACT Motivated by the proposed EXIST mission, a “medium-class” space observatory to survey black holes and the Early Universe proposed to the 2010 NAS/NRC Astronomy and Astrophysics Decadal Survey, we have developed the first “large”... more
ABSTRACT Motivated by the proposed EXIST mission, a “medium-class” space observatory to survey black holes and the Early Universe proposed to the 2010 NAS/NRC Astronomy and Astrophysics Decadal Survey, we have developed the first “large” area 256cm2 close-tiled (0.6mm gaps) hard X-ray (20–600keV) imaging detector employing pixelated (2.5mm) CdZnTe (CZT) detectors, each 2×2×0.5cm3. We summarize the design, development and operation of this detector array (8×8 CZTs) and its performance as the imager for a coded aperture telescope on a high altitude (40km) balloon flight in October, 2009, as the ProtoEXIST1 payload. We then outline our current development of a second-generation imager, ProtoEXIST2, with 0.6mm pixels on a 32×32 array on each CZT, and how it will lead to the ultimate imaging system needed for EXIST. Other applications of this technology will also be mentioned.
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B-MINE is a concept for a balloon mission designed to probe thedeepest regions of a supernova explosion by detecting Ti emission at 68 keV with spatial and spectral resolutions that are sufficient to determine the extent and velocity... more
B-MINE is a concept for a balloon mission designed to probe thedeepest regions of a supernova explosion by detecting Ti emission at 68 keV with spatial and spectral resolutions that are sufficient to determine the extent and velocity distribution of the Ti emitting region. The payload ...
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... LIKELY 22 MAGNITUDE OPTICAL COUNTERPART FOR THE X-RAY BURSTER 4U 1915 _Q51 FM WALTER,2 S. BowyER,2'3 K. 0. MASON, AND JT ... source 4U 1915-05 has been previously studied with 050 8 by Becker et aL (1977) and with... more
... LIKELY 22 MAGNITUDE OPTICAL COUNTERPART FOR THE X-RAY BURSTER 4U 1915 _Q51 FM WALTER,2 S. BowyER,2'3 K. 0. MASON, AND JT ... source 4U 1915-05 has been previously studied with 050 8 by Becker et aL (1977) and with SAS 3 (Lewin, Hoffman, and Doty ...
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Research Interests: Physics, Variable Stars, Astrometry, Astronomy, Data Reduction, and 3 moreOpen Clusters, Sky, and Astronomical
The ProtoEXIST1 mission, a pathfinder for the EXIST high energy telescope (HET), is slated for a spring 2009 flight out of Ft. Sumner, NM. The ProtoEXIST payload consists of two coded aperture telescopes, each with a 10^ 10^deg field of... more
The ProtoEXIST1 mission, a pathfinder for the EXIST high energy telescope (HET), is slated for a spring 2009 flight out of Ft. Sumner, NM. The ProtoEXIST payload consists of two coded aperture telescopes, each with a 10^ 10^deg field of view and an angular resolution of approximately 10'. One telescope will be outfitted with passive Pb/Sn/Cu rear and side shielding while the other will utilize a rear active CsI anti-coincidence shield and passive side shielding for comparison of background rejection efficiency. The detector plane of each telescope consists of a 8 times 8 large tiled array of 2.04 cm times 2.04 cm CZT detectors, each with thickness of 0.5 cm and a pixilated anode consisting of 2.5 mm pixels. Each detector is read out utilizing the Caltech RADNET ASIC. In total the detector plane of a single telescope measures 16 cm times 16 cm and is sensitive over an energy range of 10 keV up to 500 keV, with an energy resolution of 3.1 keV FWHM at 59 keV. The ProtoEXIST1 fligh...
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ABSTRACT Measurements obtained with the Utrecht (1–8 keV) and Cambridge (1–28 keV) instruments on board the Astronomical Netherlands Satellite are discussed. Particularly, the 4.8 hr period is investigated.
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... G. ZAMOBANI, M~ ELVIS, G, FABBIANO, E. FEIGELSON, R. GIACCONI, J~ GRThIDLAY, J~P~ HENRY, T. MACCACARO, S~ MURRAY, D~A~ SCHWARTZ, A. SOLTAN*, J~ STENER, IL TANANBAUM, Harvard~' Smithsonian Center for Astrophysics,... more
... G. ZAMOBANI, M~ ELVIS, G, FABBIANO, E. FEIGELSON, R. GIACCONI, J~ GRThIDLAY, J~P~ HENRY, T. MACCACARO, S~ MURRAY, D~A~ SCHWARTZ, A. SOLTAN*, J~ STENER, IL TANANBAUM, Harvard~' Smithsonian Center for Astrophysics, *Cop~r~t~ Astro nomical ...
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Observations that detected the first X-ray emission from flare stars are described. An X-ray flare was detected from YZ CMi at 0.28 keV and approximately 1-7 keV, although no optical or radio coverage was available. During a very large... more
Observations that detected the first X-ray emission from flare stars are described. An X-ray flare was detected from YZ CMi at 0.28 keV and approximately 1-7 keV, although no optical or radio coverage was available. During a very large optical flare from UV Ceti, X-ray emission at (only) 0.28 keV was detected. Upper limits for X-ray emission from several small
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... 30 (NGC 6624) is presented. The temporal and spectral variations observed in the bursts are interpreted as Compton scattering of a primary pulse in a hot cloud surrounding the X-ray source. The cloud parameters derived imply ...