R. D. Blandford
A5035206337- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Radio Astronomy Observations and Technology
- Dark Matter and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Cosmology and Gravitation Theories
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Relativity and Gravitational Theory
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- History and Developments in Astronomy
- Particle Detector Development and Performance
- Particle Accelerators and Free-Electron Lasers
- Neutrino Physics Research
- Ionosphere and magnetosphere dynamics
- Magnetic confinement fusion research
- Nuclear Physics and Applications
- Earthquake Detection and Analysis
Kavli Institute for Particle Astrophysics and Cosmology
2015-2024
Stanford University
2015-2024
SLAC National Accelerator Laboratory
2014-2023
Film Independent
2023
Menlo School
2003-2022
Foundation for Research and Technology Hellas
2022
Ames Research Center
2019
Institute of Space and Astronautical Science
2018
Max Planck Society
2018
California Institute of Technology
2000-2009
When a rotating black hole is threaded by magnetic field lines supported external currents flowing in an equatorial disc, electric potential difference will be induced. If the strength large enough, vacuum unstable to cascade production of electron–positron pairs and surrounding force-free magnetosphere established. Under these circumstances it demonstrated that energy angular momentum extracted electromagnetically. As further consequence shown charge can never contribute significantly...
(Abridged) The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on Fermi Gamma-ray Space (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering energy range from below 20 MeV to more than 300 GeV. This paper describes LAT, its pre-flight expected performance, and summarizes key science objectives that will be addressed. On-orbit performance presented in detail a subsequent paper. LAT pair-conversion telescope with precision...
We examine the possibility that energy and angular momentum are removed magnetically from accretion discs, by field lines leave disc surface extend to large distances. illustrate this mechanism solving equations of magnetohydrodynamics, assuming infinite conductivity, for axially symmetric, self-similar, cold magnetospheric flow a Keplerian in which strength B scales with radius r as |$B\,\propto\,{r}^{-5/4}$.| show centrifugally driven outflow matter is possible, if poloidal component...
(Abridged) We describe here the most ambitious survey currently planned in optical, Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST have unique capability faint time domain. The design is driven four main themes: probing dark energy matter, taking an inventory Solar System, exploring transient optical sky, mapping Milky Way. wide-field ground-based system sited at Cerro Pach\'{o}n northern Chile. telescope 8.4 m...
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...
view Abstract Citations (1990) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Relativistic jets as compact radio sources. Blandford, R. D. ; Königl, A. It is suggested that the variable emission from active galactic nuclei and quasars originates within a collimated relativistic jet of type has been inferred to supply extended sources with mass, momentum, energy directly observed in several cases. An idealized description steady presented,...
view Abstract Citations (1682) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Particle acceleration by astrophysical shocks. Blandford, R. D. ; Ostriker, J. P. A new mechanism is proposed for of a power-law distribution cosmic rays with approximately the observed slope. High-energy particles in vicinity shock are scattered Alfven waves carried converging fluid flow leading to first-order process which escape time automatically comparable...
Powerful extragalactic radio sources comprise two extended regions containing magnetic field and synchrotron-emitting relativistic electrons, each linked by a jet to central compact source located in the nucleus of associated galaxy. These jets are collimated streams plasma that emerge from opposite directions, along which flow mass, momentum, energy, flux. Methods using observations diagnostically infer pressures, densities, fluid velocities within explained. The terminate components, where...
We present the third Fermi Large Area Telescope (LAT) source catalog (3FGL) of sources in 100 MeV–300 GeV range. Based on first 4 yr science data from Gamma-ray Space mission, it is deepest yet this energy Relative to Second LAT catalog, 3FGL incorporates twice as much data, well a number analysis improvements, including improved calibrations at event reconstruction level, an updated model for Galactic diffuse γ-ray emission, refined procedure detection, and methods associating with...
ABSTRACT We present a catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), primary science instrument on Fermi Gamma-ray Space (Fermi) , during first 11 months phase mission, which began 2008 August 4. The First -LAT (1FGL) contains 1451 and characterized in 100 MeV to GeV range. Source detection was based average flux over month period, threshold likelihood Test Statistic is 25, corresponding significance just 4σ. 1FGL includes source location regions,...
Gas supplied conservatively to a black hole at rates well below the Eddington rate may not be able radiate effectively and net energy flux, including transported by viscous torque, is likely close zero all radii. This has consequence that gas accretes with positive so it escape. Accordingly, we propose only small fraction of actually falls on hole, binding releases radially outward torque as drive away remainder in form wind. generalization an alternative 'ADAF' solution. Some observational...
We present the second catalog of high-energy gamma-ray sources detected by Large Area Telescope (LAT), primary science instrument on Fermi Gamma-ray Space (Fermi), derived from data taken during first 24 months phase mission, which began 2008 August 4. Source detection is based average flux over 24-month period. The Second Fermi-LAT (2FGL) includes source location regions, defined in terms elliptical fits to 95% confidence regions and spectral power-law, exponentially cutoff or log-normal...
We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on first eight years science data from Gamma-ray Space mission in energy range 50 MeV to 1 TeV, it is deepest yet this range. Relative 3FGL catalog, 4FGL has twice as much exposure well a number analysis improvements, including an updated model for Galactic diffuse emission, and two sets light curves (1-year 2-month intervals). The includes 5064 sources above 4 sigma significance, which we provide...
The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some most dark matter (DM) dominated objects known. We report on gamma-ray observations dSphs based 6 years Fermi Large Area Telescope data processed with new Pass 8 event-level analysis. None significantly detected in gamma rays, and we present upper limits DM annihilation cross section from a combined analysis 15 dSphs. These constraints among strongest robust to date lie below canonical thermal relic for mass $\lesssim$...
A fluid dynamical treatment of an ultra-relativistic spherical blast wave enclosed by a strong shock is presented. simple similarity solution describing the explosion fixed amount energy in uniform medium derived, and this generalized to include cases which power supplied central source density external varies with radius. Radiative shocks, escaping photons carry away momentum as well energy, are also discussed. Formulas that interpolate between non- limits proposed.
We present a measurement of the Hubble constant ($H_{0}$) and other cosmological parameters from joint analysis six gravitationally lensed quasars with measured time delays. All lenses except first are analyzed blindly respect to parameters. In flat $\Lambda$CDM cosmology, we find $H_{0} = 73.3_{-1.8}^{+1.7}$, 2.4% precision measurement, in agreement local measurements $H_{0}$ type Ia supernovae calibrated by distance ladder, but $3.1\sigma$ tension $Planck$ observations cosmic microwave...
view Abstract Citations (956) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Reverberation mapping of the emission line regions Seyfert galaxies and quasars. Blandford, R. D. ; McKee, C. F. An indirect method is outlined for quasars having variable intensities profiles, provided that (1) galactic nuclei in question comprise a compact, central continuum source surrounded by an extended distribution line-emitting gas, (2) covering factor gas be...
(Abridged) We have conducted a detailed investigation of the broad-band spectral properties \gamma-ray selected blazars Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months LBAS data taking period, we were able to assemble high-quality quasi-simultaneous Spectral Energy Distributions (SED) for 48 blazars.The SED these sources is similar that...
Designed as a high-sensitivity gamma-ray observatory, the Fermi Large Area Telescope is also an electron detector with large acceptance exceeding 2 m;{2} sr at 300 GeV. Building on analysis, we have developed efficient detection strategy which provides sufficient background rejection for measurement of steeply falling spectrum up to 1 TeV. Our high precision data show that falls energy E-3.0 and does not exhibit prominent spectral features. Interpretations in terms conventional diffusive...
Black hole (BH) accretion flows and jets are qualitatively affected by the presence of ordered magnetic fields. We study fully three-dimensional global general relativistic magnetohydrodynamic (MHD) simulations radially extended thick (height $H$ to cylindrical radius $R$ ratio $|H/R|\sim 0.2--1$) around BHs with various dimensionless spins ($a/M$, BH mass $M$) initially toroidally-dominated ($\phi$-directed) poloidally-dominated ($R-z$ directed) Firstly, for toroidal field models high...
The γ-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, a residual all-sky component commonly called isotropic background (IGRB). IGRB comprises all extragalactic emissions too faint or resolved in given survey, as well any foregrounds that are approximately isotropic. first measurement Large Area Telescope (LAT) on board Fermi Gamma-ray Space (Fermi) used 10 months sky-survey...
A mechanism is proposed for the formation of radio components in strong double sources such as Cygnus A. Relativistic plasma generated an active galactic nucleus cannot escape isotropically if surrounded by too much dense thermal gas. There is, however, a possible equilibrium flow which escapes along two oppositely-directed channels or 'exhausts'. At all points on boundary these channels, pressure relativistic (possibly magnetized) must balance static gas cloud. The outflow velocity becomes...