ALBERT

Beschreibung: SUMMARY Geomagnetic polarity transitions may be significantly more complex than are currently depicted in many sedimentary and lava-flow records. By splicing together paleomagnetic results from earlier studies at Steens Mountain with those from three newly studied sections of Oregon Plateau flood basalts at Catlow Peak and Poker Jim Ridge 70–90 km to the southeast and west, respectively, we provide support for this interpretation with the most detailed account of a magnetic field reversal yet observed in volcanic rocks. Forty-five new distinguishable transitional (T) directions together with 30 earlier ones reveal a much more complex and detailed record of the 16.7 Ma reversed (R)-to-normal (N) polarity transition that marks the end of Chron C5Cr. Compared to the earlier R-T-N-T-N reversal record, the new record can be described as R-T-N-T-N-T-R-T-N. The composite record confirms earlier features, adds new west and up directions and an entire large N-T-R-T segment to the path, and fills in directions on the path between earlier directional jumps. Persistent virtual geomagnetic pole (VGP) clusters and separate VGPs have a preference for previously described longitudinal bands from transition study compilations, which suggests the presence of features at the core–mantle boundary that influence the flow of core fluid and distribution of magnetic flux. Overall the record is consistent with the generalization that VGP paths vary greatly from reversal to reversal and depend on the location of the observer. Rates of secular variation confirm that the flows comprising these sections were erupted rapidly, with maximum rates estimated to be 85–120 m ka −1 at Catlow and 130–195 m ka −1 at Poker Jim South. Paleomagnetic poles from other studies are combined with 32 non-transitional poles found here to give a clockwise rotation of the Oregon Plateau of 11.4°± 5.6° with respect to the younger Columbia River Basalt Group flows to the north and 14.5°± 4.6° with respect to cratonic North America (95 per cent confidence interval).

Beschreibung: Several persistent, low-luminosity ( L X ~ 10 34 erg s –1 ), long-spin-period ( P  〉 100 s) high-mass X-ray binaries have been reported with blackbody components with temperatures 〉1 keV. These hot thermal excesses have correspondingly small emitting regions (〈1 km 2 ) and are attributed to the neutron star polar caps. We present a recent XMM–Newton target of opportunity observation of the newest member of this class, Swift J045106.8–694803. The period was determined to be 168.5 ± 0.2 s as of 2012 July 17 (MJD = 561 25.0). At L X ~ 10 36 erg s –1 , Swift J045106.8–694803 is the brightest member of this new class, as well as the one with the shortest period. The spectral analysis reveals for the first time the presence of a blackbody with temperature $kT_{\rm BB}=1.8^{+0.2}_{-0.3}$ keV and radius R BB = 0.5 ± 0.2 km. The pulsed fraction decreases with increasing energy and the ratio between the hard (〉2 keV) and soft (〈2 keV) light curves is anticorrelated with the pulse profile. Simulations of the spectrum suggest that this is caused by the pulsations of the blackbody being ~ out of phase with those of the power-law component. Using a simple model for emission from hot spots on the neutron star surface, we fit the pulse profile of the blackbody component to obtain an indication of the geometry of the system.