Opposing shear senses in a subdetachment mylonite zone: Implications for core complex mechanics

[1] Global studies of metamorphic core complexes and low‐angle detachment faults have highlighted a fundamental problem: Since detachments excise crustal section, the relationship between the mylonitic rocks in their footwalls and the brittle deformation in their hanging walls is commonly unclear. Mylonites could either reflect ductile deformation related to exhumation along the detachment fault, or they could be a more general feature of the extending middle crust that has been “captured ” by the detachment. In the first case we would expect the kinematics of the mylonite zone to mirror the sense of movement on the detachment; in the second case both the direction and sense of shear in the mylonites could be different. The northern Snake Range décollement (NSRD) is a classic Basin and Range detachment fault with a well‐documented top‐east of displacement. We present structural, paleo-magnetic, geochronological, and geothermometric evidence to suggest that the mylonite zone below the NSRD locally experienced phases of both east ‐ and west‐directed shear, inconsistent with movement along a single detachment fault. We therefore propose that the footwall mylonites represent a predetachment dis-continuity in the middle crust that separated localized deformation above from distributed crustal flow below (localized‐distributed transition (LDT)). The mylonites were subsequently captured by a moderately dipping brittle detachment that soled down to the middle crust and exhumed them around a rolling hinge into a subhorizontal orientation at the surface, produc-ing the present‐day NSRD. In this interpretation the brittle hanging wall represents a series of rotated upper crustal normal faults, whereas the mylonitic footwall represents one or more exhumed middl

Subsystems Test Bed /STB/ Thermal Math Model /TMM/ documentation

Subsystems test bed thermal mathematical model documentatio

X-ray Timing of PSR J1852+0040 in Kesteven 79: Evidence of Neutron Stars Weakly Magnetized at Birth

The 105-ms X-ray pulsar J1852+0040 is the central compact object (CCO) in SNR Kes 79. We report a sensitive upper limit on its radio flux density of 12 uJy at 2 GHz using the NRAO GBT. Timing using XMM and Chandra over a 2.4 yr span reveals no significant change in its spin period. The 2 sigma upper limit on the period derivative leads, in the dipole spin-down formalism, to an energy loss rate E-dot < 7e33 ergs/s, surface magnetic field strength B_p < 1.5e11 G, and characteristic age tau_c = P/2P-dot > 8 Myr. This tau_c exceeds the age of the SNR by 3 orders of magnitude, implying that the pulsar was born spinning at its current period. However, the X-ray luminosity of PSR J1852+0040, L(bol) ~ 3e33(d/7.1 kpc)^2 ergs/s is a large fraction of E-dot, which challenges the rotation-powered assumption. Instead, its high blackbody temperature, 0.46+/-0.04 keV, small blackbody radius ~ 0.8 km, and large pulsed fraction, ~ 80%, may be evidence of accretion onto a polar cap, possibly from a fallback disk made of supernova debris. If B_p < 1e10 G, an accretion disk can penetrate the light cylinder and interact with the magnetosphere while resulting torques on the neutron star remain within the observed limits. A weak B-field is also inferred in another CCO, the 424-ms pulsar 1E 1207.4-5209, from its steady spin and soft X-ray absorption lines. We propose this origin of radio-quiet CCOs: the B-field, derived from a turbulent dynamo, is weaker if the NS is formed spinning slowly, which enables it to accrete SN debris. Accretion excludes neutron stars born with both B_p 0.1 s from radio pulsar surveys, where B_p 40 Myr) or recycled pulsars. Finally, such a CCO, if born in SN 1987A, could explain the non-detection of a pulsar there.Comment: 8 pages, 3 figures, to appear in The Astrophysical Journa

Thermotectonic evolution of an extensional dome: the Cenozoic Osogovo-Lisets core complex (Kraishte zone, western Bulgaria)

The Kraishte region of Bulgaria is located at the junction of the Balkanides and Hellenides-Dinarides tectonic belts. Fission-track analysis on both apatites and zircons documents the Cenozoic exhumation of a Precambrian basement bounded by low-angle detachments. Late Eocene-Oligocene extension began prior to 47Ma and was dominantly in a top-to-the-southwest direction, confirmed by the sense of younging of apatite and zircon ages. This crustal extension controlled the formation of half-graben sedimentary basins on the hanging walls of the detachments. Thermal modelling of these hanging wall units provides evidence for heat transfer across the detachments from a relatively warm rising footwall. From 32 to 29Ma, pervasive magmatic activity resulted in the emplacement of rhyolitic to dacitic subvolcanic bodies and dykes, along with intrusion of the Osogovo granite. The results give evidence for extension in the southern Balkan older than, and separated from, the Miocene to Quaternary Aegean extension. This might reflect transtension during northeastward extrusion and rotation of continental fragments around the western boundary of Moesia. Eocene-Oligocene extension seems to have been controlled by the distribution of earlier thickening all around the Carpatho-Balkanic orocline, which is reflected by the Cretaceous emplacement of the Morava Nappe in the Kraisht

X-ray Observations of the Compact Source in CTA 1

The point source RX J0007.0+7302, at the center of supernova remnant CTA 1, was studied using the X-Ray Multi-mirror Mission. The X-ray spectrum of the source is consistent with a neutron star interpretation, and is well described by a power law with the addition of a soft thermal component that may correspond to emission from hot polar cap regions or to cooling emission from a light element atmosphere over the entire star. There is evidence of extended emission on small spatial scales which may correspond to structure in the underlying synchrotron nebula. No pulsations are observed. Extrapolation of the nonthermal spectrum of RX J0007.0+7302 to gamma-ray energies yields a flux consistent with that of EGRET source 3EG J0010+7309, supporting the proposition that there is a gamma-ray emitting pulsar at the center of CTA 1. Observations of the outer regions of CTA 1 with the Advanced Satellite for Cosmology and Astrophysics confirm earlier detections of thermal emission from the remnant and show that the synchrotron nebula extends to the outermost reaches of the SNR.Comment: 5 pages, including 4 postscript figs.LaTex. Accepted for publication by Ap

X-ray Spectroscopy of Candidate Ultracompact X-ray Binaries

We present high-resolution spectroscopy of the neutron star/low-mass X-ray binaries (LMXBs) 4U 1850-087 and 4U 0513-40 as part of our continuing study of known and candidate ultracompact binaries. The LMXB 4U 1850-087 is one of four systems in which we had previously inferred an unusual Ne/O ratio in the absorption along the line of sight, most likely from material local to the binaries. However, our recent Chandra X-ray Observatory LETGS spectrum of 4U 1850-087 finds a Ne/O ratio by number of 0.22+/-0.05, smaller than previously measured and consistent with the expected interstellar value. We propose that variations in the Ne/O ratio due to source variability, as previously observed in these sources, can explain the difference between the low- and high-resolution spectral results for 4U 1850-087. Our XMM-Newton RGS observation of 4U 0513-40 also shows no unusual abundance ratios in the absorption along the line of sight. We also present spectral results from a third candidate ultracompact binary, 4U 1822-000, whose spectrum is well fit by an absorbed power-law + blackbody model with absorption consistent with the expected interstellar value. Finally, we present the non-detection of a fourth candidate ultracompact binary, 4U 1905+000, with an upper limit on the source luminosity of < 1 x 10^{32} erg s^{-1}. Using archival data, we show that the source has entered an extended quiescent state.Comment: 8 pages, 3 figures, accepted for publication to the Astrophysical Journa

Chandra Observations of the Crab-like Supernova Remnant G21.5-0.9

Chandra observations of the Crab-like supernova remnant G21.5-0.9 reveal a compact central core and spectral variations indicative of synchrotron burn-off of higher energy electrons in the inner nebula. The central core is slightly extended, perhaps indicating the presence of an inner wind-shock nebula surrounding the pulsar. No pulsations are observed from the central region, yielding an upper limit of ~40% for the pulsed fraction. A faint outer shell may be the first evidence of the expanding ejecta and blast wave formed in the initial explosion, indicating a composite nature for G21.5-0.9.Comment: 4 pages, 2 figures, formatted with emulateapj, submitted to ApJ

Guiding the Way to Gamma-Ray Sources: X-ray Studies of Supernova Remnants

Supernova remnants have long been suggested as a class of potential counterparts to unidentified gamma-ray sources. The mechanisms by which such gamma-rays can arise may include emission from a pulsar associated with a remnant, or a variety of processes associated with energetic particles accelerated by the SNR shock. Imaging and spectral observations in the X-ray band can be used to identify properties of the remnants that lead to gamma-ray emission, including the presence of pulsar-driven nebulae, nonthermal X-ray emission from the SNR shells, and the interaction of SNRs with dense surrounding material.Comment: 16 pages, 11 figures, To appear in the proceedings of the workshop: "The Nature of the Unidentified Galactic Gamma-Ray Sources" held at INAOE, Mexico, October 2000, (A.Carraminana, O. Reiner and D. Thompson, eds.

Spatially resolved XMM-Newton analysis and a model of the nonthermal emission of MSH 15-52

We present an X-ray analysis and a model of the nonthermal emission of the pulsar wind nebula (PWN) MSH15-52. We analyzed XMM-Newton data to obtain the spatially resolved spectral parameters around the pulsar PSRB1509-58. A steepening of the fitted power-law spectra and decrease in the surface brightness is observed with increasing distance from the pulsar. In the second part of this paper, we introduce a model for the nonthermal emission, based on assuming the ideal magnetohydrodynamic limit. This model is used to constrain the parameters of the termination shock and the bulk velocity of the leptons in the PWN. Our model is able to reproduce the spatial variation of the X-ray spectra. The parameter ranges that we found agree well with the parameter estimates found by other authors with different approaches. In the last part of this paper, we calculate the inverse Compton emission from our model and compare it to the emission detected with the H.E.S.S. telescope system. Our model is able to reproduce the flux level observed with H.E.S.S., but not the spectral shape of the observed TeV {\gamma}-ray emission.Comment: Accepted for publication in A&A, 9 pages, 15 figure