Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “COMPACTS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

THE PUZZLING EARLY DETECTION OF LOW VELOCITY {sup 56}Ni DECAY LINES IN SN 2014J: HINTS OF A COMPACT REMNANT

We show that the low-velocity {sup 56}Ni decay lines detected earlier than expected in the type Ia SN 2014J find an explanation in the quark-nova Ia model, which involves the thermonuclear explosion of a tidally disrupted sub-Chandrasekhar white dwarf (WD) in a tight neutron-star-WD binary system. The explosion is triggered by impact from the quark-nova (QN) ejecta on the WD material; the QN is the explosive transition of the neutron star to a quark star (QS) triggered by accretion from a CO torus (the circularized WD material). The presence of a compact remnant (the QS) provides: (1) an additional energy source (spin-down power) which allows us to fit the observed light-curve including the steep early rise; (2) a central gravitational potential which slows down some of the {sup 56}Ni produced to velocities of a few 10{sup 3} km s{sup –1}. In our model, the {sup 56}Ni decay lines become optically visible at ∼20 days from explosion time in agreement with observations. We list predictions that can provide important tests for our model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

AN EFFICIENT, COMPACT, AND VERSATILE FIBER DOUBLE SCRAMBLER FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS

We present the design and test results of a compact optical fiber double-scrambler for high-resolution Doppler radial velocity instruments. This device consists of a single optic: a high-index n ∼ 2 ball lens that exchanges the near and far fields between two fibers. When used in conjunction with octagonal fibers, this device yields very high scrambling gains (SGs) and greatly desensitizes the fiber output from any input illumination variations, thereby stabilizing the instrument profile of the spectrograph and improving the Doppler measurement precision. The system is also highly insensitive to input pupil variations, isolating the spectrograph from telescope illumination variations and seeing changes. By selecting the appropriate glass and lens diameter the highest efficiency is achieved when the fibers are practically in contact with the lens surface, greatly simplifying the alignment process when compared to classical double-scrambler systems. This prototype double-scrambler has demonstrated significant performance gains over previous systems, achieving SGs in excess of 10,000 with a throughput of ∼87% using uncoated Polymicro octagonal fibers. Adding a circular fiber to the fiber train further increases the SG to >20,000, limited by laboratory measurement error. While this fiber system is designed for the Habitable-zone Planet Finder spectrograph, it is more generally applicable to other instruments in the visible and near-infrared. Given the simplicity and low cost, this fiber scrambler could also easily be multiplexed for large multi-object instruments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A comprehensive archival search for counterparts to ultra-compact high-velocity clouds: Five Local Volume dwarf galaxies

We report five Local Volume dwarf galaxies (two of which are presented here for the first time) uncovered during a comprehensive archival search for optical counterparts to ultra-compact high-velocity clouds (UCHVCs). The UCHVC population of HI clouds are thought to be candidate gas-rich, low-mass halos at the edge of the Local Group and beyond, but no comprehensive search for stellar counterparts to these systems has been presented. Careful visual inspection of all publicly available optical and ultraviolet imaging at the position of the UCHVCs revealed six blue, diffuse counterparts with a morphology consistent with a faint dwarf galaxy beyond the Local Group. Optical spectroscopy of all six candidate dwarf counterparts show that five have an Hα-derived velocity consistent with the coincident HI cloud, confirming their association; the sixth diffuse counterpart is likely a background object. The size and luminosity of the UCHVC dwarfs is consistent with other known Local Volume dwarf irregular galaxies. The gas fraction (M{sub HI}/M{sub star}) of the five dwarfs are generally consistent with that of dwarf irregular galaxies in the Local Volume, although ALFALFA-Dw1 (associated with ALFALFA UCHVC HVC274.68+74.70–123) has a very high M{sub HI}/M{sub star} ∼ 40. Despite the heterogenous nature of our search, we demonstrate that the current dwarf companions to UCHVCs are at the edge of detectability due to their low surface brightness, and that deeper searches are likely to find more stellar systems. If more sensitive searches do not reveal further stellar counterparts to UCHVCs, then the dearth of such systems around the Local Group may be in conflict with ΛCDM simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

DOUBLE COMPACT OBJECTS. III. GRAVITATIONAL-WAVE DETECTION RATES

The unprecedented range of second-generation gravitational-wave (GW) observatories calls for refining the predictions of potential sources and detection rates. The coalescence of double compact objects (DCOs)—i.e., neutron star–neutron star (NS–NS), black hole–neutron star (BH–NS), and black hole–black hole (BH–BH) binary systems—is the most promising source of GWs for these detectors. We compute detection rates of coalescing DCOs in second-generation GW detectors using the latest models for their cosmological evolution, and implementing inspiral-merger-ringdown gravitational waveform models in our signal-to-noise ratio calculations. We find that (1) the inclusion of the merger/ringdown portion of the signal does not significantly affect rates for NS–NS and BH–NS systems, but it boosts rates by a factor of ∼1.5 for BH–BH systems; (2) in almost all of our models BH–BH systems yield by far the largest rates, followed by NS–NS and BH–NS systems, respectively; and (3) a majority of the detectable BH–BH systems were formed in the early universe in low-metallicity environments. We make predictions for the distributions of detected binaries and discuss what the first GW detections will teach us about the astrophysics underlying binary formation and evolution.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

NON-THERMAL RADIATION FROM COLLISIONS OF COMPACT OBJECTS WITH INTERMEDIATE-SCALE JETS IN ACTIVE GALAXIES

Massive black holes in active galaxies are immersed in huge concentrations of late-type stars in the galactic bulges and also early-type massive stars in the nuclear stellar clusters, which are additionally surrounded by quasi-spherical halos on a scale of several kpc that contain from a few hundred up to several thousand globular clusters (GCs). It is expected that significant numbers of red giant stars, massive stars, and also GCs can move through the jet expelled from the central engine of the active galaxy. We consider collisions of stars from the galactic bulge, nuclear cluster, and GCs with the jet plasma. As a result of such collisions, multiple shocks are expected to appear in the jet around these compact objects. Therefore, the plasma in the kpc-scale jet can be significantly disturbed. We show that particles can be accelerated on these shocks up to multi-TeV energies. TeV leptons emit synchrotron radiation, extending up to X-ray energies, and also comptonize radiation produced in a stellar cluster and also the microwave background radiation to TeV γ-ray energies. We show that such non-thermal radiation is likely to be detectable from the intermediate-scale jets of nearby active galaxies for a reasonable number of stars and GCs immersed within the jet. As an example, we calculate the expected non-thermal emission in X-ray and gamma-ray energies from the nearby radio galaxy Cen A, from which steady gamma-ray emission with a complex spectrum has recently been reported by Fermi and the HESS Observatories.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Hunting for orphaned central compact objects among radio pulsars

Central compact objects (CCOs) are a handful of young neutron stars found at the center of supernova remnants (SNRs). They show high thermal X-ray luminosities but no radio emission. Spin-down rate measurements of three CCOs with X-ray pulsations indicate surface dipole fields much weaker than those of typical young pulsars. To investigate if CCOs and known radio pulsars are objects at different evolutionary stages, we carried out a census of all weak-field (<10{sup 11} G) isolated radio pulsars in the Galactic plane to search for CCO-like X-ray emission. None of the 12 candidates are detected at X-ray energies, with luminosity limits of 10{sup 32}−10{sup 34} erg s{sup −1}. We consider a scenario in which the weak surface fields of CCOs are due to a rapid accretion of supernova materials and show that as the buried field diffuses back to the surface, a CCO descendant is expected to leave the P– P-dot parameter space of our candidates at a young age of a few ×10 kyr. Hence, the candidates are likely to just be old ordinary pulsars in this case. We suggest that further searches for orphaned CCOs, which are aged CCOs with parent SNRs that have dissipated, should include pulsars with stronger magnetic fields.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Compact radio sources within 30″ of SGR A*: Proper motions, stellar winds, and the accretion rate onto SGR A*

Recent broadband 34 and 44 GHz radio continuum observations of the Galactic center have revealed 41 massive stars identified with near-IR (NIR) counterparts, as well as 44 proplyd candidates within 30″ of Sgr A*. Radio observations obtained in 2011 and 2014 have been used to derive proper motions of eight young stars near Sgr A*. The accuracy of proper motion estimates based on NIR observations by Lu et al. and Paumard et al. have been investigated by using their proper motions to predict the 2014 epoch positions of NIR stars and comparing the predicted positions with those of radio counterparts in the 2014 radio observations. Predicted positions from Lu et al. show an rms scatter of 6 mas relative to the radio positions, while those from Paumard et al. show rms residuals of 20 mas. We also determine the mass-loss rates of 11 radio stars, finding rates that are on average ∼2 times smaller than those determined from model atmosphere calculations and NIR data. Clumpiness of ionized winds would reduce the mass loss rate of WR and O stars by additional factors of 3 and 10, respectively. One important implication of this is a reduction in the expected mass accretion rate onto Sgr A* from stellar winds by nearly an order of magnitude to a value of a few ×10{sup −7} M{sub ⊙} yr{sup −1}. Finally, we present the positions of 318 compact radio sources within 30″ of Sgr A*, 45 of which have stellar counterparts in the NIR K{sub s} (2.18 μm) and L′ (3.8 μm) bands.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

DEEP HE ii AND C iv SPECTROSCOPY OF A GIANT LYα NEBULA: DENSE COMPACT GAS CLUMPS IN THE CIRCUMGALACTIC MEDIUM OF A z ∼ 2 QUASAR

The recent discovery by Cantalupo et al. of the largest (∼500 kpc) luminous (L ≃ 1.43 × 10{sup 45} erg s{sup −1}) Lyα nebula associated with the quasar UM287 (z = 2.279) poses a great challenge to our current understanding of the astrophysics of the halos hosting massive z ∼ 2 galaxies. Either an enormous reservoir of cool gas is required M ≃ 10{sup 12} M{sub ⊙}, exceeding the expected baryonic mass available, or one must invoke extreme gas clumping factors not present in high-resolution cosmological simulations. However, observations of Lyα emission alone cannot distinguish between these two scenarios. We have obtained the deepest ever spectroscopic integrations in the He ii λ1640 and C iv λ1549 emission lines with the goal of detecting extended line emission, but detect neither line to a 3σ limiting SB ≃ 10{sup −18} erg s{sup −1} cm{sup −2} arcsec{sup −2}. We construct simple models of the expected emission spectrum in the highly probable scenario that the nebula is powered by photoionization from the central hyper-luminous quasar. The non-detection of He ii implies that the nebular emission arises from a mass M{sub c} ≲ 6.4 × 10{sup 10} M{sub ⊙} of cool gas on ∼200 kpc scales, distributed in a population of remarkably dense (n{sub H} ≳ 3 cm{sup −3}) and compact (R ≲ 20 pc) clouds, which would clearly be unresolved by current cosmological simulations. Given the large gas motions suggested by the Lyα line (v ≃ 500 km s{sup −1}), it is unclear how these clouds survive without being disrupted by hydrodynamic instabilities. Our work serves as a benchmark for future deep integrations with current and planned wide-field IFU spectrographs such as MUSE, KCWI, and KMOS. Our observations and models suggest that a ≃10 hr exposure would likely detect ∼10 rest-frame UV/optical emission lines, opening up the possibility of conducting detailed photoionization modeling to infer the physical state of gas in the circumgalactic medium.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

DISTINGUISHING COMPACT BINARY POPULATION SYNTHESIS MODELS USING GRAVITATIONAL WAVE OBSERVATIONS OF COALESCING BINARY BLACK HOLES

The coalescence of compact binaries containing neutron stars or black holes is one of the most promising signals for advanced ground-based laser interferometer gravitational-wave (GW) detectors, with the first direct detections expected over the next few years. The rate of binary coalescences and the distribution of component masses is highly uncertain, and population synthesis models predict a wide range of plausible values. Poorly constrained parameters in population synthesis models correspond to poorly understood astrophysics at various stages in the evolution of massive binary stars, the progenitors of binary neutron star and binary black hole systems. These include effects such as supernova kick velocities, parameters governing the energetics of common envelope evolution and the strength of stellar winds. Observing multiple binary black hole systems through GWs will allow us to infer details of the astrophysical mechanisms that lead to their formation. Here we simulate GW observations from a series of population synthesis models including the effects of known selection biases, measurement errors and cosmology. We compare the predictions arising from different models and show that we will be able to distinguish between them with observations (or the lack of them) from the early runs of the advanced LIGO and Virgo detectors. This will allow us to narrow down the large parameter space for binary evolution models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

THE NEXT GENERATION VIRGO CLUSTER SURVEY. X. PROPERTIES OF ULTRA-COMPACT DWARFS IN THE M87, M49, AND M60 REGIONS

We use imaging from the Next Generation Virgo cluster Survey (NGVS) to present a comparative study of ultra-compact dwarf (UCD) galaxies associated with three prominent Virgo sub-clusters: those centered on the massive red-sequence galaxies M87, M49, and M60. We show how UCDs can be selected with high completeness using a combination of half-light radius and location in color–color diagrams (u*iK{sub s} or u*gz). Although the central galaxies in each of these sub-clusters have nearly identical luminosities and stellar masses, we find large differences in the sizes of their UCD populations, with M87 containing ∼3.5 and 7.8 times more UCDs than M49 and M60, respectively. The relative abundance of UCDs in the three regions scales in proportion to sub-cluster mass, as traced by X-ray gas mass, total gravitating mass, number of globular clusters (GCs), and number of nearby galaxies. We find that the UCDs are predominantly blue in color, with ∼85% of the UCDs having colors similar to blue GCs and stellar nuclei of dwarf galaxies. We present evidence that UCDs surrounding M87 and M49 may follow a morphological sequence ordered by the prominence of their outer, low surface brightness envelope, ultimately merging with the sequence of nucleated low-mass galaxies, and that envelope prominence correlates with distance from either galaxy. Our analysis provides evidence that tidal stripping of nucleated galaxies is an important process in the formation of UCDs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

DISTRIBUTION OF FAINT ATOMIC GAS IN HICKSON COMPACT GROUPS

We present 21 cm H i observations of four Hickson Compact Groups (HCGs) with evidence for a substantial intragroup medium using the Robert C. Byrd Green Bank Telescope (GBT). By mapping H i emission in a region of 25′ × 25′ (140–650 kpc) surrounding each HCG, these observations provide better estimates of H i masses. In particular, we detected 65% more H i than that detected in the Karl G. Jansky Very Large Array (VLA) imaging of HCG 92. We also identify whether the diffuse gas has the same spatial distribution as the high surface brightness (HSB) H i features detected in the VLA maps of these groups by comparing the H i strengths between the observed and modeled masses based on VLA maps. We found that the H i observed with the GBT has a similar spatial distribution to the HSB structures in HCG 31 and HCG 68. Conversely, the observed H i distributions in HCG 44 and HCG 92 were extended and showed significant offsets from the modeled masses. Most of the faint gas in HCG 44 lies to the northeast–southwest region and in HCG 92 lies in the northwest region of their respective groups. The spatial and dynamical similarities between the total (faint+HSB) and the HSB H i indicate that the faint gas is of tidal origin. We found that the gas will survive ionization by the cosmic UV background and the escaping ionizing photons from the star-forming regions and stay primarily neutral for at least 500 Myr.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Star formation suppression in compact group galaxies: A new path to quenching?

We present CO(1–0) maps of 12 warm H{sub 2}-selected Hickson Compact Groups (HCGs), covering 14 individually imaged warm H{sub 2} bright galaxies, with the Combined Array for Research in Millimeter Astronomy. We found a variety of molecular gas distributions within the HCGs, including regularly rotating disks, bars, rings, tidal tails, and possibly nuclear outflows, though the molecular gas morphologies are more consistent with spirals and early-type galaxies than mergers and interacting systems. Our CO-imaged HCG galaxies, when plotted on the Kennicutt–Schmidt relation, shows star formation (SF) suppression of 〈 S 〉=10±5, distributed bimodally, with five objects exhibiting suppressions of S ≳ 10 and depletion timescales ≳10 Gyr. This SF inefficiency is also seen in the efficiency per freefall time of Krumholz et al. We investigate the gas-to-dust ratios of these galaxies to determine if an incorrect L{sub CO}–M(H{sub 2}) conversion caused the apparent suppression and find that HCGs have normal gas-to-dust ratios. It is likely that the cause of the apparent suppression in these objects is associated with shocks injecting turbulence into the molecular gas, supported by the fact that the required turbulent injection luminosity is consistent with the bright H{sub 2} luminosity reported by Cluver et al. Galaxies with high SF suppression (S ≳ 10) also appear to be those in the most advanced stages of transition across both optical and infrared color space. This supports the idea that at least some galaxies in HCGs are transitioning objects, where a disruption of the existing molecular gas in the system suppresses SF by inhibiting the molecular gas from collapsing and forming stars efficiently. These observations, combined with recent work on poststarburst galaxies with molecular reservoirs, indicates that galaxies do not need to expel their molecular reservoirs prior to quenching SF and transitioning from blue spirals to red early-type galaxies. This may imply that SF quenching can occur without the need to starve a galaxy of cold gas first.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

THE QUaD GALACTIC PLANE SURVEY. II. A COMPACT SOURCE CATALOG

We present a catalog of compact sources derived from the QUaD Galactic Plane Survey. The survey covers {approx}800 deg{sup 2} of the inner galaxy (|b| < 4{sup 0}) in Stokes I, Q, and U parameters at 100 and 150 GHz, with angular resolutions of 5 and 3.5 arcmin, respectively. Five hundred and twenty-six unique sources are identified in I, of which 239 are spatially matched between frequency bands, with 53 (234) detected at 100 (150) GHz alone; 170 sources are identified as ultracompact H II regions. Approximating the distribution of total intensity source fluxes as a power law, we find a slope of {gamma}{sub S,100} = -1.8 {+-} 0.4 at 100 GHz and {gamma}{sub S,150} = -2.2 {+-} 0.4 at 150 GHz. Similarly, the power-law index of the source two-point angular correlation function is {gamma}{sub {theta},100} = -1.21 {+-} 0.04 and {gamma}{sub {theta},150} = -1.25 {+-} 0.04. The total intensity spectral index distribution peaks at {alpha}{sub I} {approx} 0.25, indicating that dust emission is not the only source of radiation produced by these objects between 100 and 150 GHz; free-free radiation is likely significant in the 100 GHz band. Four sources are detected in polarized intensity P, of which three have matching counterparts in I. Three of the polarized sources lie close to the Galactic center, Sagittarius A*, Sagittarius B2, and the Galactic Radio Arc, while the fourth is RCW 49, a bright H II region. An extended polarized source, undetected by the source extraction algorithm on account of its {approx}0.{sup 0}5 size, is identified visually, and is an isolated example of large-scale polarized emission oriented distinctly from the bulk Galactic dust polarization.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE AUSTRALIA TELESCOPE COMPACT ARRAY H I SURVEY OF THE GALACTIC CENTER

We present a survey of atomic hydrogen (H I) emission in the direction of the Galactic Center (GC) conducted with the CSIRO Australia Telescope Compact Array (ATCA). The survey covers the area -5 Degree-Sign {<=} l {<=} +5 Degree-Sign , -5 Degree-Sign {<=} b {<=} +5 Degree-Sign over the velocity range -309 km s{sup -1} {<=} v{sub LSR} {<=} 349 km s{sup -1} with a velocity resolution of 1 km s{sup -1}. The ATCA data are supplemented with data from the Parkes Radio Telescope for sensitivity to all angular scales larger than the 145'' angular resolution of the survey. The mean rms brightness temperature across the field is 0.7 K, except near (l, b) = 0 Degree-Sign , 0 Degree-Sign where it increases to {approx}2 K. This survey complements the Southern Galactic Plane Survey to complete the continuous coverage of the inner Galactic plane in H I at {approx}2' resolution. Here, we describe the observations and analysis of this GC survey and present the final data product. Features such as Bania's Clump 2, the far 3 kpc arm, and small high-velocity clumps are briefly described.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

KINETIC THEORY OF EQUILIBRIUM AXISYMMETRIC COLLISIONLESS PLASMAS IN OFF-EQUATORIAL TORI AROUND COMPACT OBJECTS

The possible occurrence of equilibrium off-equatorial tori in the gravitational and electromagnetic fields of astrophysical compact objects has been recently proved based on non-ideal magnetohydrodynamic theory. These stationary structures can represent plausible candidates for the modeling of coronal plasmas expected to arise in association with accretion disks. However, accretion disk coronae are formed by a highly diluted environment, and so the fluid description may be inappropriate. The question is posed of whether similar off-equatorial solutions can also be determined in the case of collisionless plasmas for which treatment based on kinetic theory, rather than a fluid one, is demanded. In this paper the issue is addressed in the framework of the Vlasov-Maxwell description for non-relativistic, multi-species axisymmetric plasmas subject to an external dominant spherical gravitational and dipolar magnetic field. Equilibrium configurations are investigated and explicit solutions for the species kinetic distribution function are constructed, which are expressed in terms of generalized Maxwellian functions characterized by isotropic temperature and non-uniform fluid fields. The conditions for the existence of off-equatorial tori are investigated. It is proved that these levitating systems are admitted under general conditions when both gravitational and magnetic fields contribute to shaping the spatial profiles of equilibrium plasma fluid fields. Then, specifically, kinetic effects carried by the equilibrium solution are explicitly provided and identified here with diamagnetic energy-correction and electrostatic contributions. It is shown that these kinetic terms characterize the plasma equation of state by introducing non-vanishing deviations from the assumption of thermal pressure.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Compact Muon Production and Collection Scheme for High-Energy Physics Experiments

The relative immunity of muons to synchrotron radiation suggests that they might be used in place of electrons as probes in fundamental high-energy physics experiments. Muons are commonly produced indirectly through pion decay by interaction of a charged particle beam with a target. However, the large angle and energy dispersion of the initial beams as well as the short muon lifetime limits many potential applications. Here, we describe a fast method for manipulating the longitudinal and transverse phase-space of a divergent pion-muon beam to enable efficient capture and downstream transport with minimum losses. We also discuss the design of a handling system for the removal of unwanted secondary particles from the target region and thus reduce activation of the machine. The compact muon source we describe can be used for fundamental physics research in neutrino experiments.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Minimum magnetic curvature for resilient divertors using Compact Toroidal Hybrid geometry

The properties of resilient divertors are explored using equilibria derived from Compact Toroidal Hybrid (CTH) geometries. Resilience is defined here as the robustness of the strike point patterns as the plasma geometry and/or plasma profiles are changed. The addition of plasma current in the CTH configurations significantly alters the shape of the last closed flux surface and the rotational transform profile, however, it does not alter the strike point pattern on the target plates, and hence has resilient divertor features. The limits of when a configuration transforms to a resilient configuration is then explored. New CTH-like configurations are generated that vary from a perfectly circular cross section to configurations with increasing amounts of toroidal shaping. It is found that even small amounts of toroidal shaping lead to strike point localization that is similar to the standard CTH configuration. Lastly, these results show that only a small degree of three-dimensional shaping is necessary to produce a resilient divertor, implying that any highly shaped optimized stellarator will possess the resilient divertor property.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Dark matter mini-halo around the compact objects: the formation, evolution and possible contribution to the cosmic ray electrons/positrons

Dark matter particles may be captured by a star and then thermalized in the star's core. At the end of its life a massive star collapses suddenly and a compact object is formed. The dark matter particles redistribute accordingly. In the inelastic dark matter model, an extended dense dark matter mini-halo surrounding the neutron star may be formed. Such mini-halos may be common in the Galaxy. The electron/positron flux resulting in the annihilation of dark matter particles, however, is unable to give rise to observable signal unless a nascent mini-halo is within a distance ∼ a few 0.1 pc from the Earth.

79 ASTRONOMY AND ASTROPHYSICS↗