10,399 research outputs found
Periodic functions for Hecke triangle groups, and the Seiberg zeta functions as a Fredholm determinant
Discovery of an outflow of the very low-mass star ISO 143
We discover that the very young very low-mass star ISO143 (M5) is driving an
outflow based on spectro-astrometry of forbidden [SII] emission lines at 6716A
and 6731A observed in UVES/VLT spectra. This adds another object to the handful
of brown dwarfs and very low-mass stars (M5-M8) for which an outflow has been
confirmed and which show that the T Tauri phase continues at very low masses.
We find the outflow of ISO143 to be intrinsically asymmetric and the accretion
disk to not obscure the outflow, as only the red outflow component is visible
in the [SII] lines. ISO143 is only the third T Tauri object showing a stronger
red outflow component in spectro-astrometry, after RW Aur (G5) and ISO217
(M6.25). We show here that including ISO143 two out of seven outflows confirmed
in the very low-mass regime (M5-M8) are intrinsically asymmetric. We measure a
spatial extension of the outflow in [SII] of up to 200-300 mas (about 30-50 AU)
and velocities of up to 50-70 km/s. We furthermore detect line emission of
ISO143 in CaII (8498), OI (8446), HeI (7065), and weakly in [FeII] (7155).
Based on a line profile analysis and decomposition we demonstrate that (i) the
CaII emission can be attributed to chromospheric activity, a variable wind, and
the magnetospheric infall zone, (ii) the OI emission mainly to
accretion-related processes but also a wind, and (iii) the HeI emission to
chromospheric or coronal activity. We estimate a mass outflow rate of ISO143 of
~10^{-10} Msol/yr and a mass accretion rate in the range of ~10^{-8} to
~10^{-9} Msol/yer. These values are consistent with those of other brown dwarfs
and very low-mass stars. The derived Mout/Macc ratio of 1-20% is not supporting
previous findings of this number to be very large (>40%) for very low-mass
objects.Comment: Accepted for publication at A&A; 9 pages, 5 figures. Minor changes
due to language editin
Muonic hydrogen and the proton radius puzzle
The extremely precise extraction of the proton radius by Pohl et al. from the
measured energy difference between the 2P and 2S states of muonic hydrogen
disagrees significantly with that extracted from electronic hydrogen or elastic
electron-proton scattering. This is the proton radius puzzle. The origins of
the puzzle and the reasons for believing it to be very significant are
explained. Various possible solutions of the puzzle are identified, and future
work needed to resolve the puzzle is discussed.Comment: Minor modifications, some references added, to appear in Annu. Rev.
Nucl. Part. Sci. Vol 63 (2013). 60 pages, 5 figures, 1 tabl
Oxidation of an oil rich in docosahexaenoic acid compared to linoleic acid in lactating women
Background: We studied the oxidation of an oil rich in docosahexaenoic acid (DHA; DHASCO(R)) in lactating mothers receiving a dietary DHA supplement or a placebo. The results were compared with the oxidation of linoleic acid. Methods: Breast-feeding mothers received a dietary supplement (DHASCO; 200 mg DHA/day, n = 5) or a placebo (n = 5) for 14 days. Six weeks post partum all 10 mothers received a single dose of 2 mg/kg body weight uniformly C-13-labeled DHASCO. In a previously reported study 6 mothers received 1 mg/kg body weight uniformly C-13-labeled linoleic acid. Breath samples were collected over 48 h after tracer application. The total CO2 production was measured by indirect calorimetry and the C-13 isotopic enrichment of labeled CO2 by isotopic ratio mass spectrometry. Results: The oxidation of C-13-labeled DHASCO in the supplemented and placebo groups was similar. Maximal C-13 enrichment was reached earlier in the group receiving C-13-DHASCO (median 1.0 vs. 3.0 h in the linoleic acid group). The cumulative C-13 recovery in breath was higher in the DHASCO versus the linoleic acid group until 10 h after tracer application and comparable thereafter. Conclusions: The difference in oxidation of DHASCO versus linoleic acid after tracer ingestion might be partly due to a faster absorption and oxidation of shorter chain saturated fatty acids contained in DHASCO. The cumulative oxidation of DHASCO and linoleic acid 24 and 48 h after tracer ingestion is similar. Copyright (C) 2000 S. Karger AG, Basel
Quasi-elastic neutrino charged-current scattering cross sections on oxygen
The charged-current quasi-elastic scattering of muon neutrinos on oxygen
target is computed for neutrino energies between 200 MeV and 2.5 GeV using the
relativistic distorted-wave impulse approximation with relativistic optical
potential, which was earlier successfully applied to describe electron-nucleus
data. We study both neutrino and electron processes and show that the reduced
exclusive cross sections for neutrino and electron scattering are similar. The
comparison with the relativistic Fermi gas model (RFGM), which is widely used
in data analyses of neutrino experiments, shows that the RFGM fails completely
when applied to exclusive cross section data and leads to overestimated values
of inclusive and total cross sections. We also found significant nuclear-model
dependence of exclusive, inclusive and total cross sections for about 1 GeV
energy.Comment: 30 pages, 11 figures; final version to appear in Phys. Rev.
Analysis of GeV-band gamma-ray emission from SNR RX J1713.7-3946
RX J1713.7-3946 is the brightest shell-type Supernova remnant (SNR) of the
TeV gamma-ray sky. Earlier Fermi-LAT results on low-energy gamma-ray emission
suggested that, despite large uncertainties in the background determination,
the spectrum is inconsistent with a hadronic origin. We update the GeV-band
spectra using improved estimates for the diffuse galactic gamma-ray emission
and more than doubled data volume. We further investigate the viability of
hadronic emission models for RX J1713.7-3946. We produced a high-resolution map
of the diffuse Galactic gamma-ray background corrected for HI self-absorption
and used it in the analysis of more than 5~years worth of Fermi-LAT data. We
used hydrodynamic scaling relations and a kinetic transport equation to
calculate the acceleration and propagation of cosmic-rays in SNR. We then
determined spectra of hadronic gamma-ray emission from RX J1713.7-3946,
separately for the SNR interior and the cosmic-ray precursor region of the
forward shock, and computed flux variations that would allow to test the model
with observations. We find that RX J1713.7-3946 is now detected by Fermi-LAT
with very high statistical significance, and the source morphology is best
described by that seen in the TeV band. The measured spectrum of RX
J1713.7-3946 is hard with index gamma=1.53 +/- 0.07, and the integral flux
above 500 MeV is F = (5.5 +/- 1.1)e-9 photons/cm^2/s. We demonstrate that
scenarios based on hadronic emission from the cosmic-ray precursor region are
acceptable for RX J1713.7-3946, and we predict a secular flux increase at a few
hundred GeV at the level of around 15% over 10 years, which may be detectable
with the upcoming CTA observatory.Comment: 9 pages, accepted for publication in Astronomy & Astrophysic
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