1,364 research outputs found
Boosting Higgs discovery - the forgotten channel
Searches for a heavy Standard Model Higgs boson focus on the 'gold plated
mode' where the Higgs decays to two leptonic Z bosons. This channel provides a
clean signature, in spite of the small leptonic branching ratios. We show that
using fat jets the semi-leptonic ZZ mode significantly increases the number of
signal events with a similar statistical significance as the leptonic mode.Comment: 12 pages, 3 figure
Eclipsing high-mass binaries I. Light curves and system parameters for CPD-518946, PISMIS24-1 and HD319702
We present first results of a comprehensive photometric O-star survey
performed with a robotic twin refractor at the Universit\"atssternwarte Bochum
located near Cerro Armazones in Chile. For three high-mass stars, namely
Pismis24-1, CPD-518946 and HD319702, we determined the period through the
Lafler-Kinman algorithm and model the light curves within the framework of the
Roche geometry. For Pismis24-1, a previously known eclipsing binary, we provide
first light curves and determined a photometric period of 2.36 days together
with an orbital inclination of 61.8 degrees. The best-fitting model solution to
the light curves suggest a detached configuration. With a primary temperature
of T1 = 42520K we obtain the temperature of the secondary component as T2 =
41500K. CPD-518946 is another known eclipsing binary for which we present a
revised photometric period of 1.96 days with an orbital inclination of 58.4
degrees. The system has likely a semi-detached configuration and a mass ratio q
= M1/M2 = 2.8. If we adopt a primary temperature of T1 = 34550K we obtain T2 =
21500K for the secondary component. HD319702 is a newly discovered eclipsing
binary member of the young open cluster NGC6334. The system shows well-defined
eclipses favouring a detached configuration with a period of 2.0 days and an
orbital inclination of 67.5 degrees. Combining our photometric result with the
primary spectral type O8 III(f) (T1 = 34000K) we derive a temperature of T2 =
25200K for the secondary component.Comment: 7 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
The broad-line region and dust torus size of the Seyfert 1 galaxy PGC50427
We present the results of a three years monitoring campaigns of the type-1 active galactic nucleus (AGN) PGC50427. Through the use of
Photometric Reverberation Mapping with broad and narrow band filters, we
determine the size of the broad-line emitting region by measuring the time
delay between the variability of the continuum and the H emission line.
The H emission line responds to blue continuum variations with an
average rest frame lag of days. Using single epoch spectroscopy
we determined a broad-line H velocity width of 1020 km s and in
combination with the rest frame lag and adoption a geometric scaling factor , we calculate a black hole mass of . Using the flux variation gradient method, we separate the host
galaxy contribution from that of the AGN to calculate the rest frame 5100\AA~
luminosity at the time of our monitoring campaign. The rest frame lag and the
host-subtracted luminosity permit us to derive the position of PGC50427 in the
BLR size -- AGN luminosity diagram, which is remarkably close to the
theoretically expected relation of . The simultaneous
optical and NIR ( and ) observations allow us to determine the size
of the dust torus through the use of dust reverberation mapping method. We find
that the hot dust emission () lags the optical variations with an
average rest frame lag of days. The dust reverberation radius
and the nuclear NIR luminosity permit us to derive the position of PGC50427 on
the known diagram. The simultaneus observations for the
broad-line region and dust thermal emission demonstrate that the innermost dust
torus is located outside the BLR in PGC50427, supporting the unified scheme for
AGNs. (Abstract shortened, see the manuscript.)Comment: 11 pages, 23 figures, accepted for publication in Astronomy and
Astrophysic
Fast radio burst dispersion measures and rotation measures and the origin of intergalactic magnetic fields
We investigate the possibility of measuring intergalactic magnetic fields using the dispersion measures and rotation measures of fast radio bursts. With Bayesian methods, we produce probability density functions for values of these measures. We distinguish between contributions from the intergalactic medium, the host galaxy, and the local environment of the progenitor. To this end, we use constrained, magnetohydrodynamic simulations of the local Universe to compute lines-of-sight integrals from the position of the Milky Way. In particular, we differentiate between predominantly astrophysical and primordial origins of magnetic fields in the intergalactic medium. We test different possible types of host galaxies and probe different distribution functions of fast radio burst progenitor locations inside the host galaxy. Under the assumption that fast radio bursts are produced by magnetars, we use analytic predictions to account for the contribution of the local environment. We find that less than 100 fast radio bursts from magnetars in stellar-wind environments hosted by starburst dwarf galaxies at redshift z âł 0.5 suffice to discriminate between predominantly primordial and astrophysical origins of intergalactic magnetic fields. However, this requires the contribution of the Milky Way to be removed with a precision of â1 rad m-2. We show the potential existence of a subset of fast radio bursts whose rotation measures carry information on the strength of the intergalactic magnetic field and its origins
Lifetime measurements in Co and Co
Lifetimes of the and states in Co and the
state in Co were measured using the recoil distance Doppler
shift and the differential decay curve methods. The nuclei were populated by
multi-nucleon transfer reactions in inverse kinematics. Gamma rays were
measured with the EXOGAM Ge array and the recoiling fragments were fully
identified using the large-acceptance VAMOS spectrometer. The E2 transition
probabilities from the and states to the ground
state could be extracted in Co as well as an upper limit for the
(E2) value in Co. The experimental
results were compared to large-scale shell-model calculations in the and
model spaces, allowing to draw conclusions on the single-particle
or collective nature of the various states.Comment: 8 pages, 8 figures, 1 table, accepted for publication in Physical
Review
Observation of isotonic symmetry for enhanced quadrupole collectivity in neutron-rich 62,64,66Fe isotopes at N=40
The transition rates for the 2_{1}^{+} states in 62,64,66Fe were studied
using the Recoil Distance Doppler-Shift technique applied to projectile Coulomb
excitation reactions. The deduced E2 strengths illustrate the enhanced
collectivity of the neutron-rich Fe isotopes up to N=40. The results are
interpreted by the generalized concept of valence proton symmetry which
describes the evolution of nuclear structure around N=40 as governed by the
number of valence protons with respect to Z~30. The deformation suggested by
the experimental data is reproduced by state-of-the-art shell calculations with
a new effective interaction developed for the fpgd valence space.Comment: 4 pages, 2 figure
The progenitor of the FUor-type young eruptive star 2MASS J06593158â0405277
Only a dozen confirmed FU Orionis-type young outbursting stars (FUors) are known today; this explains the interest in the recent FUor eruption of 2MASS J06593158â0405277. Its outburst and expected decline will be subject to numerous studies in the future. Almost equally important for the understanding of the eruption mechanism, however, is the physical characterization of the FUorâs precursor. Here we analyze unpublished archival data and summarize â and partly revise â all relevant photometry from optical to submillimeter wavelengths. Our analysis implies that the FUor is possibly associated with eight T Tauri star candidates and a strong Class 0 source. Adopting a distance of 450 pc for the FUor, we derive a quiescent bolometric luminosity and temperature of Lbol = 4.8 Lâ and Tbol = 1190 K , typical for young Class II sources. The central star has a temperature of Teff = 4000 K, a mass of 0.75 Mâ, and an age of about 6Ă105 yr. The SED implies a circumstellar mass of 0.01 â 0.06 Mâ, and the system is surrounded by a faint infrared nebulosity. Our results provide an almost complete picture of a FUor progenitor, supporting the interpretation of future post-outburst studies
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