A5070431412- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Experimental and Theoretical Physics Studies
- Astro and Planetary Science
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Solar and Space Plasma Dynamics
- Advanced X-ray Imaging Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Particle Accelerators and Free-Electron Lasers
- Spacecraft Dynamics and Control
- Scientific Research and Discoveries
- Planetary Science and Exploration
- Adaptive optics and wavefront sensing
- High-pressure geophysics and materials
- Historical Astronomy and Related Studies
- Atomic and Subatomic Physics Research
- Ionosphere and magnetosphere dynamics
- Spacecraft Design and Technology
Grossmont College
2015-2024
San Diego State University
2016-2024
United States Naval Academy
2019
University of California, San Diego
1994-2005
University of Edinburgh
1990
The High Energy X-Ray Timing Experiment (HEXTE) is one of three scientific instruments aboard the Rossi Explorer (RXTE), which was launched on 1995 December 30. RXTE performs timing and spectral studies bright X-ray sources to determine physical parameters these systems. HEXTE consists two independent clusters detectors, each cluster containing four NaI(Tl)/CsI(Na) phoswich scintillation counters sharing a common 1° FWHM field view. view switched off source provide near real-time background...
We present the 2-60 keV spectrum of supernova remnant Cassiopeia A measured using Proportional Counter Array and High Energy X-Ray Timing Experiment on Rossi Explorer satellite. In addition to previously reported strong emission-line features produced by thermal plasmas, broadband has a high-energy "tail" that extends energies at least as high 120 keV. This tail may be described broken power law photon indices Γ1 = 1.8+ 0.5−0.6 Γ2 3.04+ 0.15−0.13 break energy Eb 15.9+ 0.3−0.4 argue...
The Coma Cluster was observed in 1996 for ≃90 ks by the PCA and HEXTE instruments aboard Rossi X-ray Timing Explorer (RXTE) satellite—the first simultaneous, pointing measurement of broad, 2-250 keV energy band. high sensitivity achieved during this long observation allows precise determination spectrum. Our analysis measurements clearly indicates that addition to main thermal emission from hot intracluster gas at kT ≃ 7.5 keV, a second spectral component is required best fit data. If...
We identify the extended Einstein IPC X-ray source, 1E0657-56, with a previously unknown cluster of galaxies at redshift $z=0.296$. Optical CCD images show presence gravitational arc in this and galaxy spectra yield velocity dispersion $1213^{+352}_{-191}$ km s$^{-1}$. data obtained ROSAT HRI ASCA indicate that 1E0657-56 is highly luminous which merger subclusters may be occurring. The temperature hot gas $\rm{kT}=17.4 \pm 2.5 keV$, makes it an unusually cluster, important cosmological implications.
We present the results of a 17 ks Chandra ACIS-S observation nearby dwarf spiral galaxy NGC 4395. affords first high-quality, broadband X-ray detection active nucleus this object that is uncontaminated by sources in field. find nuclear source to be unresolved and confirm rapid, large-amplitude variability reported previous studies. The light curve appears show ∼11 cycles quasi-periodic oscillation with period ∼400 s. If associated an orbital feature near innermost stable orbit accretion...
We report the detection of broad (FWHM 270 km s-1) H I · 21 cm absorption toward compact (<15 h-1 pc) radio nucleus nearby powerful galaxy Cygnus A. The corresponds to a column density hydrogen atoms at least 2.54 ± 0.44 × 1019 Tspin cm-2. Observations OH and H2CO yielded upper limits. While other possibilities exist, we argue that observed plausibly occurs within circumnuclear obscuring torus which is thought block our direct view quasar in this object.
NGC 4945 is one of the brightest Seyfert galaxies on sky at 100 keV, but completely absorbed below 10 keV; its absorption column probably largest that still allows a direct view nucleus hard X-ray energies. Our observations it with Rossi X-Ray Timing Explorer (RXTE) satellite confirm large absorption, which for simple phenomenological fit using an absorber solar abundances implies 4.5+0.4-0.4x1024 cm(-2). Using more realistic scenario (requiring Monte Carlo modeling scattering), we infer...
We report spectroscopic observations at |$\lambda /\delta \lambda \simeq 300$| of the Paschen β hydrogen recombination line in narrow X-ray galaxies NGC 5506 and A0945 – 30 ( = MCG-5-23-16), Seyfert 2 galaxy 4388. The profiles are both found to possess broad components |$\,\text{FWHM}\gt 1500\,\text{km s}^{-1};$| this removes previous controversy concerning presence their Hα profiles. use optical, X -ray mid-infrared data estimate extinction towards continuum sources these objects order test...
We present simultaneous infrared and X-ray observations of the Galactic microquasar GRS 1915+105 using Palomar 5 m telescope Rossi X-Ray Timing Explorer on 1998 July 10 UT. Over course hr, we observed six faint (IR) flares with peak amplitudes approximately 0.3-0.6 mJy durations 500-600 s. These are associated soft-dip/soft-flare cycles, as opposed to brighter IR hard-dip/soft-flare cycles seen in 1997 August by Eikenberry et al. Interestingly, begin before oscillations, implying an...
We present the results of observations PSR B1509-58/MSH 15-52 system in X-rays (2-250 keV) by Rossi X-Ray Timing Explorer. The spectra peak pulsed component (radio phase 0.17-0.53) is fitted a power law photon index 1.36±0.01, with no evidence high-energy spectral break seen up to ~200 keV. For off-pulse component, spectrum from 2-250 keV 2.215±0.005. An iron emission line at 6.7 an equivalent width 129 eV improves fit, but only marginal significance. Thermal bremsstrahlung and Raymond-Smith...
view Abstract Citations (61) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared Spectroscopy of Cygnus A: Implications for the Obscured Active Nucleus Ward, Martin J. ; Blanco, Philip R. Wilson, Andrew S. Nishida, Minoru We present near-infrared spectroscopic observations central regions luminous radio galaxy A (3C 405) and interpret these results in terms an obscured quasar nucleus. have detected strong emission molecular hydrogen lines...
Abstract We present the results of ASCA observations Seyfert galaxy Mkn 463. find that 1–10 keV X-ray spectrum consists at least two components: soft and hard. have found no evidence for a strong Fe-K fluorescent line (equivalent width &lt; 670 eV). The component dominates below 4 has steep slope; 0.2–4 flux is consistent with determined from Einstein observations. It would appear this emission comes distinct thermal component. hard component, which been detected first time by ASCA, only...
The role of work and mechanical energy in classical relativity has been a subject renewed interest this publication. Here we present problem that illustrates the relationship between impulse kinetic for rocket-powered object can also change its gravitational potential energy. same introductory physics principles lead to remarkable result when applied mechanics spaceflight—the Oberth effect—whereby small cause large rocket’s orbital without violating any conservation laws.
Abstract The citizen Continental-America Telescopic Eclipse (CATE) Experiment was a new type of science experiment designed to capture time sequence white-light coronal observations during totality from 17:16 18:48 UT on 2017 August 21. Using identical instruments the CATE group imaged inner corona 1 2.1 RSun with 1.″43 pixels at cadence s. A slow mass ejection (CME) started SW limb Sun before total eclipse began. An analysis data 17:22 17:39 maps spatial distribution flow velocities about...
We present the result of near-infrared spectroscopic observations on radio galaxy 3C 22 (z=0.937). Contrary to previous classification this object as a narrow-line galaxy, we report clear presence broad Hα line, showing directly that at least some powerful galaxies are simply reddened quasars.
We report the detection with ROSAT of a transient X-ray source at R.A. 17h44m331 and decl. -28°44'29'' (J2000), which we identify bursting pulsar GRO J1744-28. have made K-band observations ESO US Naval Observatory, Flagstaff Station. A counterpart this previously identified by us on an image taken 1996 February 8 Blanco et al. is found to be detected during only two (of seven) short exposures composed. cannot definitely reject reality variable object but feel that it not possible rule out...
The Rossi X-Ray Timing Explorer made a short (10 ks) observation of the radio galaxy Centaurus A on 1996 August 14. Analysis combined 2.5-240 keV spectrum has revealed heavily absorbed (NH=9.42±0.24×1022 cm-2) primary power law (Γ=1.86±0.015) and an iron line due to fluorescence cold matter (EW=162±25 eV). Flux from jet, flux scattered into sight, or seen through partial absorber was not required. iron-line width is unresolved at 95% confidence level (σ<0.54 keV). No significant variability...
We present results from a series of optical (g- and r-band) near-infrared (K'-band) observations the region sky including entire Rossi X-Ray Timing Explorer ROSAT error circles for "Bursting Pulsar," GRO J1744-28. These data were taken with Astrophysical Research Consortium's 3.5 m telescope at Apache Point Observatory 2.2 European Southern Observatory. see no new object, or any significant brightening known in these circles, exception an object detected our 1996 February 8 image. This has...
You have a rocket in high circular orbit around massive central body (a planet or the Sun) and wish to escape with fastest possible speed at infinity for given amount of fuel. In 1929, Hermann Oberth showed that firing two separate impulses (one retrograde one prograde) can be more effective than direct transfer expends all fuel once. This is due effect, whereby small impulse applied periapsis produce large change rocket's orbital mechanical energy, without violating energy conservation....
Most rockets convert the energy stored in their propellant mass into mechanical required to expel it as exhaust. The 'rocket equation', which describes how a rocket's speed changes with mass, is usually derived by assuming that this fuel expelled at constant relative velocity. However, poor assumption for cases where rocket promptly loses large fraction of its mass. Instead, I derive change emits N discrete pellets, produced per unit In model find greatest when all once (N = 1). limit many...
A rocket in free space accelerates from rest by continuously expelling fuel; as its speed increases, mass decreases. At what (and remaining mass) does the carry maximum momentum? Maximum kinetic energy? The answers provide insights into dynamics of variable-mass systems, and have applications to planetary defense that are engaging for students introductory mechanics.
In November 2014 the Rosetta mission to Comet 67P/Churyumov-Gerasimenko made headlines when its Philae lander completed a successful unpowered descent onto surface of comet nucleus after “7 hours terror” for scientists. 67P's irregular shape and rotation this task even more challenging. fell almost radially towards 67P, as shown in an animation produced by European Space Agency (ESA) prior event. Below, we investigate whether it is possible model spacecraft's time impact speed using concepts...
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