2,532 research outputs found
Anti-Pluricanonical Systems On Q-Fano Threefolds
We investigate birationality of the anti-pluricanonical map , the
rational map defined by the anti-pluricanonical system , on
-Fano threefolds.Comment: 18 page
X-ray follow-ups of XSSJ12270-4859: a low-mass X-ray binary with gamma ray FERMI-LAT association
XSSJ1227.0-4859 is a peculiar, hard X-ray source recently positionally
associated to the Fermi-LAT source 1FGLJ1227.9-4852/2FGLJ1227.7-4853.
Multi-wavelength observations have added information on this source, indicating
a low-luminosity low-mass X-ray binary (LMXB), but its nature is still unclear.
To progress in our understanding, we present new X-ray data from a monitoring
campaign performed in 2011 with the XMM-Newton, RXTE, and Swift satellites and
combine them with new gamma-ray data from the Fermi and AGILE satellites. We
complement the study with simultaneous near-UV photometry from XMM-Newton and
with previous UV/optical and near-IR data. The X-ray history of XSSJ1227.0-4859
over 7yr shows a persistent and rather stable low-luminosity (~6x10^33
d_{1\,kpc}^2 erg/s) source, with flares and dips being peculiar and permanent
characteristics. The associated Fermi-LAT source 2FGLJ1227.7-4853 is also
stable over an overlapping period of 4.7\,yr. Searches for X-ray fast
pulsations down to msec give upper limits to pulse fractional amplitudes of
15-25% that do not rule out a fast spinning pulsar. The combined
UV/optical/near-IR spectrum reveals a hot component at ~13\,kK and a cool one
at ~4.6\,kK. The latter would suggest a late-type K2-K5 companion star, a
distance range of1.4--3.6kpc and an orbital period of 7--9 h. A near-UV
variability (>6\,h) also suggests a longer orbital period than previously
estimated. The analysis shows that the X-ray and UV/optical/near-IR emissions
are more compatible with an accretion-powered compact object than with a
rotational powered pulsar. The X-ray to UV bolometric luminosity ratio could be
consistent with a binary hosting a neutron star, but the uncertainties in the
radio data may also allow an LMXB black hole with a compact jet. In this case
it would be the first associated with a high-energy gamma-ray source.Comment: 17 pages, 14 figures, 1 table; Accepted for publication in Astronomy
& Astrophysics Main Journa
Atomic masses of intermediate-mass neutron-deficient nuclei with relative uncertainty down to 35-ppb via multireflection time-of-flight mass spectrograph
High-precision mass measurements of Cu, Zn, Ga,
Ge, As, Br, Rb, and Sr were performed
utilizing a multireflection time-of-flight mass spectrograph combined with the
gas-filled recoil ion separator GARIS-II. In the case of Ga, a mass
uncertainty of 2.1 keV, corresponding to a relative precision of , was obtained and the mass value is in excellent agreement
with the 2016 Atomic Mass Evaluation. For Ge and Br, where masses
were previously deduced through indirect measurements, discrepancies with
literature values were found. The feasibility of using this device for mass
measurements of nuclides more neutron-deficient side, which have significant
impact on the -process pathway, is discussed.Comment: 15 pages, 6 figures, 1 tabl
Three embeddings of the Klein simple group into the Cremona group of rank three
We study the action of the Klein simple group G consisting of 168 elements on
two rational threefolds: the three-dimensional projective space and a smooth
Fano threefold X of anticanonical degree 22 and index 1. We show that the
Cremona group of rank three has at least three non-conjugate subgroups
isomorphic to G. As a by-product, we prove that X admits a Kahler-Einstein
metric, and we construct a smooth polarized K3 surface of degree 22 with an
action of the group G.Comment: 43 page
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