Martin Elvis

How many ore-bearing asteroids?

Abstract A simple formalism is presented to assess how many asteroids contain ore, i.e., commercially profitable material, and not merely a high concentration of a resource. I apply this formalism to two resource cases: platinum group metals (PGMs) and water. Assuming for now that only Ni–Fe asteroids are of interest for PGMs, then 1% of NEOs are rich in PGMs. The dearth of ultra-low delta-v ( 100xa0m diameter. These estimates are at present highly imprecise and sensitive to small changes, especially in the maximum delta-v allowed. Nonetheless the low values found here mean that much improved determinations of each of the terms of the formalism are urgently needed. If better estimates still find small numbers of ore-bearing NEOs then thorough surveys for NEA discovery and, especially, characterization are needed. Strategies for the two classes are likely to be different.

Chandra discovery of a 100 kpc X-ray jet in PKS 0637-752

The quasar PKS 0637-753, the first celestial X-ray target of the Chandra X-ray Observatory, has revealed asymmetric X-ray structure extending from 3 to 12 arcsec west of the quasar, coincident with the inner portion of the jet previously detected in a 4.8 GHz radio image (Tingay et al. 1998). At a redshift of z=0.651, the jet is the largest (~100 kpc) and most luminous (~10^{44.6} ergs/s) of the few so far detected in X-rays. This letter presents a high resolution X-ray image of the jet, from 42 ks of data when PKS 0637-753 was on-axis and ACIS-S was near the optimum focus. For the inner portion of the radio jet, the X-ray morphology closely matches that of new ATCA radio images at 4.8 and 8.6 GHz. Observations of the parsec scale core using the VSOP space VLBI mission show structure aligned with the X-ray jet, placing important constraints on the X-ray source models. HST images show that there are three small knots coincident with the peak radio and X-ray emission. Two of these are resolved, which we use to estimate the sizes of the X-ray and radio knots. The outer portion of the radio jet, and a radio component to the east, show no X-ray emission to a limit of about 100 times lower flux. nThe X-ray emission is difficult to explain with models that successfully account for extra-nuclear X-ray/radio structures in other active galaxies. We think the most plausible is a synchrotron self-Compton (SSC) model, but this would imply extreme departures from the conventional minimum-energy and/or homogeneity assumptions. We also rule out synchrotron or thermal bremsstrahlung models for the jet X-rays, unless multicomponent or ad hoc geometries are invoked.

The Chandra COSMOS Legacy Survey: Energy Spectrum of the Cosmic X-Ray Background and Constraints on Undetected Populations

Using {em Chandra} observations in the 2.15 deg

Double-peaked profiles : ubiquitous signatures of disks in the broad emission lines of active galactic nuclei

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HIDDEN ACTIVE GALACTIC NUCLEI IN EARLY-TYPE GALAXIES

COSMOS legacy field, we present one of the most accurate measurements of the Cosmic X-ray Background (CXB) spectrum to date in the [0.3-7] keV energy band. The CXB has three distinct components: contributions from two Galactic collisional thermal plasmas at kT

Mapping Seyfert and LINER Excitation Modes in the Inner kpc of NGC 3393

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X-Ray Emission from the Nuclear Region of Arp 220

0.27 and 0.07 keV and an extragalactic power-law with photon spectral index

Quasar Rain: The Broad Emission Line Region as Condensations in the Warm Accretion Disk Wind

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CHEERS results from NGC 3393 : II. Investigating the extended narrow-line region using deep Chandra observations and Hubble Space Telescope narrow-line imaging

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How many assay probes to find one ore-bearing asteroid?

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