A5004065675- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Galaxies: Formation, Evolution, Phenomena
- Radio Astronomy Observations and Technology
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Particle Detector Development and Performance
- Geophysics and Sensor Technology
- Astrophysics and Star Formation Studies
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Dark Matter and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Nuclear Physics and Applications
- Medical Imaging Techniques and Applications
- GNSS positioning and interference
- Neutrino Physics Research
- High-pressure geophysics and materials
- Advanced X-ray Imaging Techniques
Columbia University
2006-2024
Quest University Canada
2009-2016
Beverly Hospital
2016
Association of Universities For Research In Astronomy
2000-2003
U.S. National Science Foundation
2000-2003
Kitt Peak National Observatory
2000-2003
University of Cambridge
1993-2001
Institute of Astronomy
1994-2001
Goddard Space Flight Center
1986
University of Massachusetts Amherst
1977
view Abstract Citations (2408) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The FIRST Survey: Faint Images of the Radio Sky at Twenty Centimeters Becker, Robert H. ; White, Richard L. Helfand, David J. survey to produce centimeters is now underway using NRAO Very Large Array. We describe here scientific motivation for a large-area sky radio frequencies which has sensitivity and angular resolution comparable Palomar Observatory Survey, we...
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates band from 3 to 79 keV, extending sensitivity of far beyond ∼10 keV cutoff achieved by all previous satellites. inherently low background associated with concentrating light enables probe hard sky a more than 100-fold improvement over collimated or coded mask instruments that have operated this bandpass. Using its unprecedented...
We present a catalog of 138,665 radio sources derived from the initial 1550 deg2 FIRST survey. The survey parameters are reviewed, and map depicting coverage for first two observing sessions is presented. then describe in detail our algorithm source detection parameterization, as well procedures constructing final catalog. results extensive tests astrometric photometric accuracy, uncertainties extent morphological characterization, Source positions all good to better than 1'', flux density...
The Palomar Transient Factory (PTF) is a wide-field experiment designed to investigate the optical transient and variable sky on time scales from minutes years. PTF uses CFH12k mosaic camera, with field of view 7.9 deg2 plate scale 1'' pixel-1, mounted Observatory 48 inch Samuel Oschin Telescope. operation strategy devised probe existing gaps in phase space search for theoretically predicted, but not yet detected, phenomena, such as fallback supernovae, macronovae,. Ia orphan afterglows...
view Abstract Citations (834) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Einstein (HEAO 2) X-ray Observatory. Giacconi, R. ; Branduardi, G. Briel, U. Epstein, A. Fabricant, D. Feigelson, E. Forman, W. Gorenstein, P. Grindlay, J. Gursky, H. Harnden, F. Henry, Jones, C. Kellogg, Koch, Murray, S. Schreier, Seward, Tananbaum, Topka, K. Van Speybroeck, L. Holt, Becker, Boldt, Serlemitsos, Clark, Canizares, Markert, T. Novick, Helfand,...
The FIRST survey, begun over twenty years ago, provides the definitive high-resolution map of radio sky. This VLA survey reaches a 20cm detection sensitivity 1 mJy 10,575 deg**2 largely coincident with SDSS area. Images and catalog containing 946,432 sources are available through web site (http://sundog.stsci.edu). We record here authoritative history, including hardware software changes that affect catalog's reliability completeness. use recent JVLA observations to test astrometry flux...
We present the Multi-Array Galactic Plane Imaging Survey (MAGPIS), which maps portions of first quadrant with an angular resolution, sensitivity, and dynamic range that surpass existing radio images Milky Way by more than order magnitude. The source detection threshold at 20 cm is in 1-2 mJy over 85% survey region (5° < l 32°, |b| 08) not covered bright extended emission; resolution ∼6''. catalog 3000 discrete sources (diameters mostly <30'') atlas ∼400 diffuse emission regions. New archival...
view Abstract Citations (432) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A solf X-ray study of the Large Magellanic Cloud. Long, K. S. ; Helfand, D. J. Grabelsky, A. It is estimated on statistical grounds that 97 sources detected in a survey Cloud (LMC) by means Einstein Laboratory's imaging telescope, less than 25 are likely to be either foreground stars or background quasars. The largest class identified discovered supernova remnants...
We present high-resolution Chandra X-ray observations of PSR B0833-45, the 89 ms pulsar associated with Vela supernova remnant. have acquired two separated by 1 month to search for changes in and its environment following an extreme glitch rotation frequency. find a well-resolved nebula toroidal morphology remarkably similar that observed Crab Nebula, along axial Crab-like jet. Between observations, taken ~3 × 105 s 106 after glitch, flux from is found be steady within 0.75%; 3 σ limit on...
We have used the Very Large Array (VLA) FIRST survey and Automated Plate Measuring Facility (APM) catalog of Palomar Observatory Sky Survey I (POSS-I) plates as basis for constructing a new radio-selected sample optically bright quasars. This is first that competitive in size with current selected quasar surveys. Using only two basic criteria, radio-optical positional coincidence optical morphology, quasars BL Lac objects can be identified 60% selection efficiency; efficiency increases to...
view Abstract Citations (234) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A 5 GHz VLA Survey of the Galactic Plane Becker, Robert H. ; White, Richard L. Helfand, David J. Zoonematkermani, S. We have used Very Large Array (VLA) to survey inner Galaxy (absolute value b less than 0.4 deg, l = 350-40 deg) at a limiting sensitivity between 2.5 and 10 mJy. The has resulted in catalog 1272 discrete sources (including 100 outside formal area)...
We present a technique to explore the radio sky into nanoJansky regime by employing image stacking using FIRST survey. first discuss non-intuitive relationship between mean and median values of distribution that is dominated noise, followed an analysis systematic effects in FIRST's 20cm VLA snapshot images. Image allows us recover properties source populations with fluxes factor 30 or more below rms noise level. Mean estimates flux density, luminosity, etc., are derivable for any class...
We present a near-infrared quasar composite spectrum spanning the wavelength range 0.58 - 3.5 um. The has been constructed from observations of 27 quasars obtained at NASA IRTF telescope and satisfying criteria Ks < 14.5 Mi -23; redshift is 0.118 z 0.418. signal-to-noise moderate, reaching maximum 150 between 1.6 1.9 While power-law fit to continuum requires two breaks, single slope alpha=-0.92 plus 1260 K blackbody provides an excellent description H-alpha um, strongly suggesting...
view Abstract Citations (283) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Supernova remnants in the Magellanic Clouds. [FORMAT HHMM+DD.d] Mathewson, D. S. ; Ford, V. L. Dopita, M. A. Tuohy, I. R. Long, K. Helfand, J. The present updated catalog of SNRs Large and Small Clouds (LMC SMC) incorporates recently discovered as a result coordinated X-ray, optical, radio surveys, contains 25 confirmed LMC six SMC. Optical images are included for...
view Abstract Citations (165) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Pulsar timing .III. Timing noise of 50 pulsars. Cordes, J. M. ; Helfand, D. An examination the behavior pulsars has shown that activity is more than 50% correlated with pulsar period derivative, weakly period, and uncorrelated radio luminosity, galactic altitude, other source parameters. upper limit placed on for binary PSR 1913 + 16 consistent its small derivative....
view Abstract Citations (169) References (67) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Classification of IRAS-selected X-Ray Galaxies in the ROSAT All-Sky Survey Moran, Edward C. ; Halpern, Jules P. Helfand, David J. To explore possibility that star-forming galaxies or obscured Seyfert galaxies, both which are known to be luminous infrared sources, contribute significantly cosmic X-ray background, we have carried out an extensive program obtain...
The infrared-luminous galaxy NGC 3256 is a classic example of merger-induced nuclear starburst system. We find here that it the most X-ray-luminous star-forming yet detected (L0.5-10 keV = 1.6 × 1042 ergs s-1). Long-slit optical spectroscopy and deep, high-resolution ROSAT X-ray image show driving "superwind" which accounts for ~20% observed soft emission. Analysis spectral data from ASCA indicates this gas has characteristic temperature kT ≈ 0.3 keV. Our model broadband emission contains...
We present an investigation of the spectral and spatial structure X-ray emission from 3C 58 based on a 350 ks observation with Chandra Observatory. This deep image, obtained as part Large Project program, reveals new information nearly all scales in pulsar wind nebula (PWN). On smallest we derive improved limit T < 1.02 X 10^6 K for blackbody entire surface central neutron star (NS), confirming need rapid, nonstandard cooling stellar interior. Furthermore, show that data are consistent...
We have discovered two low-ionization broad absorption line quasars in programs to obtain optical spectra for radio-selected quasar candidates from the VLA FIRST Survey (Becker, White, & Helfand 1995). Both belong extremely rare class of BAL QSOs that exhibit narrow lines metastable excited levels Fe II and III. Until now, there was just a single object this class, 0059-2735 (Hazard et al. 1987). In addition, one our new objects is first known radio-loud QSO. The properties these three...
view Abstract Citations (185) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Discovery of a 50 millisecond pulsar in the Large Magellanic Cloud. Seward, F. D. ; Harnden, R., Jr. Helfand, J. The authors have discovered ms X-ray Crab-like LMC supernova remnant 0540-693. is spinning down with P= 4.79×10-13s s-1, implying characteristic age 1660 yr and an energy loss rate E= 1.5×1038ergs one-third that Crab pulsar. luminosity surrounding nebula...
Combining radio observations with optical and infrared color selection, demonstrated in our pilot study to be an efficient selection algorithm for finding red quasars, we have obtained spectroscopy 120 objects a complete sample of 156 candidates from sky area 2716 deg2. Consistent initial results, find that criteria (J - K > 1.7, R 4.0) yield ~50% success rate discovering quasars substantially redder than those found surveys. Comparison UVX- color-selected samples shows ≳10% the are missed...
We report on observations of a type II quasar at redshift z = 3.288, identified as hard X-ray source in 185 ks observation with the Chandra X-Ray Observatory and high-redshift photometric candidate from deep, multiband optical imaging. CXO J084837.9+445352 (hereafter 52) shows an unusually spectrum which we infer absorbing column density NH (4.8 ± 2.1) × 1023 cm-2 (90% confidence) implied unabsorbed 2-10 keV rest-frame luminosity L2-10 3.3 1044 ergs s-1, well within regime. Hubble Space...
view Abstract Citations (144) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS ASCA Observations of the Large Magellanic Cloud Supernova Remnant Sample: Typing Supernovae from Their Remnants Hughes, John P. ; Hayashi, Ichizo Helfand, David Hwang, Una Itoh, Masayuki Kirshner, Robert Koyama, Katsuji Markert, Thomas Tsunemi, Hiroshi Woo, Jonathan We present our first results a study supernova remnants (SNRs) in (LMC) using data ASCA. The three we...
view Abstract Citations (150) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Catalog of Small-Diameter Radio Sources in the Galactic Plane Zoonematkermani, S. ; Helfand, D. J. Becker, R. H. White, L. Perley, A. survey plane longitude range -20^deg^ <= l 120^deg^ for latitudes |b| 0.8^deg^ has been carried out at 1400 MHz using VLA B configuration. We present here a catalog 1992 discrete sources detected this which is ~ 75% complete to...