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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Baryogenesis in extended inflation. 2: Baryogenesis via primordial black holes

Baryogenesis at the end of extended inflation is studied. Extended inflation is brought to an end by the collisions of bubble walls surrounding regions of true vacuum, a process which produces particles well out of thermal equilibrium. The possibility that the wall collisions may provide a significant density of primordial black holes is considered and their possible role in generating a baryon asymmetry is examined.

Barrow, John D.↗
NASA NTRS2010

The Fermi Gamma-Ray Space Telescope, Exploding Stars, Neutron Stars, and Black Holes

Since August, 2008, the Fermi Gamma-ray Space Telescope has been scanning the sky, producing a full-sky image every three hours. These cosmic gamma-rays come from extreme astrophysical phenomena, many related to exploding stars (supernovae) or what these explosions leave behind: supernova remnants, neutron stars, and black holes. This talk uses sample Fermi results, plus simple demonstrations, to illustrate the exotic properties of these endpoints of stellar evolution.

Thompson, David J.↗
NASA NTRS2019

Tests of General Relativity With the Binary Black Hole Signals from the LIGO-Virgo Catalog GWTC-1

The detection of gravitational waves by Advanced LIGO and Advanced Virgo provides an opportunity to test general relativity in a regime that is inaccessible to traditional astronomical observations and laboratory tests. We present four tests of the consistency of the data with binary black hole gravitational waveforms predicted by general relativity. One test subtracts the best-fit waveform from the data and checks the consistency of the residual with detector noise. The second test checks the consistency of the low- and high-frequency parts of the observed signals. The third test checks that phenomenological deviations introduced in the waveform model (including in the post-Newtonian coefficients) are consistent with 0. The fourth test constrains modifications to the propagation of gravitational waves due to a modified dispersion relation, including that from a massive graviton. We present results both for individual events and also results obtained by combining together particularly strong events from the first and second observing runs of Advanced LIGO and Advanced Virgo, as collected in the catalog GWTC-1. We do not find any inconsistency of the data with the predictions of general relativity and improve our previously presented combined constraints by factors of 1.1 to 2.5. In particular, we bound the mass of the graviton to be 𝑚𝑔≤4.7×10 −23 eV/𝑐 2 (90% credible level), an improvement of a factor of 1.6 over our previously presented results. Additionally, we check that the four gravitational-wave events published for the first time in GWTC-1 do not lead to stronger constraints on alternative polarizations than those published previously.

B P Abbott↗
DOE OSTI2021

Hot and dense quark-gluon plasma thermodynamics from holographic black holes

We present new results on the equation of state and transition line of hot and dense strongly interacting QCD matter, obtained from a bottom-up Einstein-Maxwell-Dilaton holographic model. We considerably expand the previous coverage in baryon densities in this model by implementing new numerical methods to map the holographic black hole solutions onto the QCD phase diagram. We are also able to obtain, for the first time, the first-order phase transition line in a wide region of the phase diagram. Comparisons with the most recent lattice results for the QCD thermodynamics are also presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1989

Space telescope searches for black holes in galactic nuclei

The Hubble Space Telescope (HST) will allow astronomers to obtain luminosity profiles, rotation curves, and velocity dispersions at angular scales that are an order of magnitude superior to those obtained previously. This enhanced spatial resolution will greatly improve the sensitivity for detecting centrally condensed matter in nearby galactic nuclei including, possibly, black holes.

Harms, Richard J.↗
NASA NTRS1992

Soft gamma rays from black holes versus neutron stars

The recent launches of GRANAT and GRO provide unprecedented opportunities to study compact collapsed objects from their hard x ray and gamma ray emissions. The spectral range above 100 keV can now be explored with much higher sensitivity and time resolution than before. The soft gamma ray spectral data is reviewed of black holes and neutron stars, radiation, and particle energization mechanisms and potentially distinguishing gamma ray signatures. These may include soft x ray excesses versus deficiencies, thermal versus nonthermal processes, transient gamma ray bumps versus power law tails, lines, and periodicities. Some of the highest priority future observations are outlines which will shed much light on such systems.

Liang, Edison P.↗
DOE OSTI2023

Comptonization by reconnection plasmoids in black hole coronae – III. Dependence on the guide field in pair plasma

ABSTRACT We perform non-radiative two-dimensional particle-in-cell simulations of magnetic reconnection for various strengths of the guide field (perpendicular to the reversing field), in magnetically dominated electron–positron plasmas. Magnetic reconnection under such conditions could operate in accretion disc coronae around black holes. There, it has been suggested that the transrelativistic bulk motions of reconnection plasmoids containing inverse-Compton-cooled electrons could Compton-upscatter soft photons to produce the observed non-thermal hard X-rays. Our simulations are performed for magnetizations 3 ≤ σ ≤ 40 (defined as the ratio of enthalpy density of the reversing field to plasma enthalpy density) and guide field strengths 0 ≤ Bg/B0 ≤ 1 (normalized to the reversing field strength B0). We find that the mean bulk energy of the reconnected plasma depends only weakly on the flow magnetization but strongly on the guide field strength – with Bg/B0 = 1 yielding a mean bulk energy twice smaller than Bg/B0 = 0. Similarly, the dispersion of bulk motions around the mean – a signature of stochasticity in the plasmoid chain’s motions – is weakly dependent on magnetization (for σ ≳ 10) but strongly dependent on the guide field strength – dropping by more than a factor of two from Bg/B0 = 0 to Bg/B0 = 1. In short, reconnection in strong guide fields (Bg/B0 ∼ 1) leads to slower and more ordered plasmoid bulk motions than its weak guide field (Bg/B0 ∼ 0) counterpart.

Astronomy & Astrophysics↗
NASA NTRS1988

On the formation of black holes

The paper explores the consequences of the existence of a burning process beyond ordinary nuclear processes (which stop at iron), involving the 'strange' particles. In effect, this idea has already had considerable discussion within the high energy physics community in terms of 'quark' matter. A possible consequence is that neutron stars may explode rather than collapse to black holes. It should be evident that such a possibility suggests radically new scenarios for activity in galactic nuclei and gamma ray burst sources.

Michel, F. Curtis↗
NASA NTRS1986

The black hole binary A0620-00

CCD photometry obtained with the 1.3-m McGraw-Hill telescope during 1981-1985 and 490-560-nm spectra obtained at KPNO on Jan. 17, 1985, are reported for A0620-00. The mass of the compact X-ray source is found to have lower limit 3.20 solar mass, strongly implying that it is a black hole; its mass is shown to exceed 7.3 solar mass if the K dwarf fills its Roche lobe during quiescence.

Mcclintock, J. E.↗
NASA NTRS2012

On the Determination of the Spin of the Black Hole in Cyg X-1 from X-Ray Reflection Spectra

The spin of Cygnus X-I is measured by fitting reflection models to Suzaku data covering the energy band 0.9-400 keY. The inner radius of the accretion disc is found to lie within 2 gravitational radii (rg = GM/c(exp 2)) and a value for the dimensionless black hole spin is obtained of 0.97(sup .0.14) (sup -0.02). This agrees with recent measurements using the continuum fitting method by Gou et al. and of the broad iron line by Duro et al. The disc inclination is measured at 23.7(sup +6.7) (sup -5.4) deg. which is consistent with the recent optical measurement of the binary system inclination by Orosz et al of 27+/- 0.8 deg. We pay special attention to the emissivity profile caused by irradiation of the inner disc by the hard power-law source. 1be X-ray observations and simulations show that the index q of that profile deviates from the commonly used, Newtonian, value of 3 within 3r(sub g), steepening considerably within 2r(sub g). as expected in the strong gravity regime.

Fabian, A. C.↗
DOE OSTI2025

From capture to collapse: Revisiting black hole formation by fermionic asymmetric dark matter in neutron stars

Fermionic asymmetric dark matter (ADM) can be captured in neutron stars (NSs) via scatterings with the star constituents. The absence of dark matter annihilation due to its asymmetric nature leads to ADM accumulation in the NS core, potentially reaching densities sufficient to exceed the Chandrasekhar limit and trigger its gravitational collapse into a black hole (BH), eventually consuming the NS from within. Therefore, the existence and observation of old neutron stars provide a means to constrain the properties of ADM. We revisit previous constraints on the mass and scattering cross section off neutrons of fermionic ADM across a class of models. We critically examine common simplifying approximations used in the literature to derive these limits. Our analysis includes improved treatments of dark matter capture, thermalization, BH formation, accretion, and evaporation. We find that previous results can be relaxed by a few orders of magnitude once these effects are properly accounted for.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1979

GX339-4 - A new black hole candidate

HEAO-1 observations of aperiodic variability in the galactic X-ray source GX339-4 (4U 1658-48) on time scales of tens of milliseconds to a few seconds are reported. It is shown that the overall characteristics of GX339-4 place it in the same class of X-ray sources as Cyg X-1 and Cir X-1, which are candidates for black holes in binary systems. The detection of X-ray flares from GX339-4 is discussed, particularly a series of five sequential flares with separations of about 250 ms.

Samimi, J.↗
NASA NTRS1972

Further evidence for a black hole in Beta Lyrae.

Comments regarding an interpretation of the OAO-2 observations of Beta Lyrae are presented. This interpretation had been reported by Wilson (1971). Six color UV curves represent the first continual coverage of a single cycle of Beta Lyr. Explanations for the deepening secondary minimum in the far UV are discussed. It is pointed out that the secondary component is apparently a massive object. The 'black hole' model represents one approach to interpret the observations of Beta Lyr.

Kondo, Y.↗
NASA NTRS1985

The natural angular momentum distribution in the study of thick disks around black holes

The thick-disk model is reviewed with an angular momentum distribution chosen to have a power-law relation with the von Zeipel parameter lambda = sq rt(l/Omega), where l denotes the specific angular momentum and Omega denotes the angular velocity. This choice permits the integration of the relativistic Euler equation independent of the background geometry. The consequences with regard to the Schwarzschild and Kerr black-hole geometries are briefly investigated.

Chakrabarti, S. K.↗
NASA NTRS2018

Black Holes and Neutron Stars in Nearby Galaxies: Insights from NuSTAR

Nearby galaxy surveys have long classified X-ray binaries (XRBs) by the mass category of their donor stars (high-mass and low-mass). The NuSTAR (Nuclear Spectroscopic Telescope Array) observatory, which provides imaging data at E greater than 10 keV (kiloelectronvolts), has enabled the classification of extragalactic XRBs by their compact object type: neutron star (NS) or black hole (BH). We analyzed NuSTAR/Chandra/XMM-Newton observations from a NuSTAR-selected sample of 12 galaxies within 5 Mpc (megaparsecs) having stellar masses (M (sub asterisk)) 10 (sup 7-11) solar masses and star formation rates (SFRs) approximately 0.01-15 solar masses per year. We detected 128 NuSTAR sources to a sensitivity of 10 (sup 38) ergs per second. Using NuSTAR color-intensity and color-color diagrams we classified 43 of these sources as candidate NSs and 47 as candidate BHs. We further subdivide BHs by accretion states (soft, intermediate, and hard) and NSs by weak (Z/Atoll) and strong (accreting pulsar) magnetic field. Using eight normal (Milky Way-type) galaxies in the sample, we confirm the relation between the SFR and galaxy X-ray point source luminosity in the 4-25 and 12-25 keV energy bands. We also constrained galaxy X-ray point source luminosity using the relation L (sub X) equals M (sub asterisk) plus Beta SFR, finding agreement with previous work. The X-ray luminosity function (XLF) of all sources in the 4-25 and 12-25 keV energy bands matches the alpha = 1.6 slope for high-mass XRBs. We find that NS XLFs suggest a decline beginning at the Eddington limit for a 1.4 solar mass NS, whereas the BH fraction shows an approximate monotonic increase in the 4-25 and 12-25 keV energy bands. We calculate the overall ratio of BH to NS to be approximately 1 for 4-25 keV and approximately 2 for 12-25 keV.

Vulic, N.↗
NASA NTRS1996

Periodic outbursts from the black hole candidate 4U 1630-47

Observational data from several observatories, including Rosat, are used to identify two previously unreported outbursts from the ultrasoft X-ray transient 4U 1630-47. These outbursts occurred in March 1979 and September 1993, which is consistent with a previously reported 600-day outburst recurrence period. This source is a member of the class of transient X-ray binary systems that are thought to contain black holes. The 601.0 +/- 2.8 day period is the shortest observed so far for this class.

Parmar, A. N.↗
NASA NTRS1983

Visual slant misperception and the Black-Hole landing situation

A theory which explains the tendency for dangerously low approaches during night landing situations is presented. The two dimensional information at the pilot's eye contains sufficient information for the visual system to extract the angle of slant of the runway relative to the approach path. The analysis is depends upon perspective information which is available at a certain distance out from the aimpoint, to either side of the runway edgelights. Under black hole landing conditions, however, this information is not available, and it is proposed that the visual system use instead the only available information, the perspective gradient of the runway edgelights. An equation is developed which predicts the perceived approach angle when this incorrect parameter is used. The predictions are in close agreement with existing experimental data.

Perrone, J. A.↗
NASA NTRS1984

Visual slant misperception and the 'black-hole' landing situation

A theory which explains the tendency for dangerously low approaches during night landing situations is presented. The two-dimensional information at the pilot's eye contains sufficient information for the visual system to extract the angle of slant of the runway relative to the approach path. The analysis depends upon perspective information which is available at a certain distance out from the aimpoint, to either side of the runway edgelights. Under black hole landing conditions, however, this information is not available, and it is proposed that the visual system use instead the only available information, the perspective gradient of the runway edgelights. An equation is developed which predicts the perceived approach angle when this incorrect parameter is used. The predictions are in close agreement with existing experimental data.

Perrone, J. A.↗