2,077 research outputs found
Multi-site observations of Delta Scuti stars 7 Aql and 8 Aql (a new Delta Scuti variable): The twelfth STEPHI campaign in 2003
We present an analysis of the pulsation behaviour of the Delta Scuti stars 7
Aql (HD 174532) and 8 Aql (HD 174589) -- a new variable star -- observed in the
framework of STEPHI XII campaign during 2003 June--July. 183 hours of high
precision photometry were acquired by using four-channel photometers at three
sites on three continents during 21 days. The light curves and amplitude
spectra were obtained following a classical scheme of multi-channel photometry.
Observations in different filters were also obtained and analyzed. Six and
three frequencies have been unambiguously detected above a 99% confidence level
in the range 0.090 mHz--0.300 mHz and 0.100 mHz-- 0.145 mHz in 7 Aql and 8 Aql
respectively. A comparison of observed and theoretical frequencies shows that 7
Aql and 8 Aql may oscillate with p modes of low radial orders, typical among
Delta Scuti stars. In terms of radial oscillations the range of 8 Aql goes from
n=1 to n=3 while for 7 Aql the range spans from n=4 to n=7. Non-radial
oscillations have to be present in both stars as well. The expected range of
excited modes according to a non adiabatic analysis goes from n=1 to n=6 in
both stars.Comment: 8 pages, 7 fugures, 5 tables, accepted for publication in
Astronomical Journa
Pulsational frequencies of the eclipsing delta-Scuti star HD 172189
The eclipsing delta-Scuti star HD 172189 is a probable member of the open
cluster IC 4756 and a promising candidate target for the CoRoT mission.
The detection of pulsation modes is the first step in the asteroseismological
study of the star. Further, the calculation of the orbital parameters of the
binary system allows us to make a dynamical determination of the mass of the
star, which works as an important constraint to test and calibrate the
asteroseismological models.
From a detailed frequency analysis of 210 hours of photometric data of HD
172189 obtained from the STEPHI XIII campaign we have identified six pulsation
frequencies with a confidence level of 99% and a seventh with a 65% confidence
level in the range between 100-300 uHz. In addiction, three eclipses were
observed during the campaign, allowing us to improve the determination of the
orbital period of the system.Comment: 6 pages, 7 figure
New multisite observations of Delta Scuti stars V624 Tauri and HD 23194
The preliminary results of STEPHI 2006 campaign are reported.Comment: To be published in Communications in Asteroseismolgy: Special Issu
Study of the D^0 \to pi^-pi^+pi^-pi^+ decay
Using data from the FOCUS (E831) experiment at Fermilab, we present new
measurements for the Cabibbo-suppressed decay mode . We measure the branching ratio .
An amplitude analysis has been performed, a first for this channel, in order to
determine the resonant substructure of this decay mode. The dominant component
is the decay , accounting for 60% of the decay rate.
The second most dominant contribution comes from the decay , with a fraction of 25%. We also study the
line shape and resonant substructure. Using the helicity formalism for the
angular distribution of the decay , we measure
a longitudinal polarization of %.Comment: 38 pages, 8 figures. accepted for publication in Physical Review
A Study of D0 --> K0(S) K0(S) X Decay Channels
Using data from the FOCUS experiment (FNAL-E831), we report on the decay of
mesons into final states containing more than one . We present
evidence for two Cabibbo favored decay modes, and
, and measure their combined branching fraction
relative to to be = 0.0106
0.0019 0.0010. Further, we report new measurements of
=
0.0179 0.0027 0.0026, = 0.0144 0.0032 0.0016,
and = 0.0208 0.0035 0.0021 where the first error is
statistical and the second is systematic.Comment: 11 pages, 3 figures, typos correcte
A Measurement of the Ds+ Lifetime
A high statistics measurement of the Ds+ lifetime from the Fermilab
fixed-target FOCUS photoproduction experiment is presented. We describe the
analysis of the two decay modes, Ds+ -> phi(1020)pi+ and Ds+ ->
\bar{K}*(892)0K+, used for the measurement. The measured lifetime is 507.4 +/-
5.5 (stat.) +/- 5.1 (syst.) fs using 8961 +/- 105 Ds+ -> phi(1020)pi+ and 4680
+/- 90 Ds+ -> \bar{K}*(892)0K+ decays. This is a significant improvement over
the present world average.Comment: 5 pages, 3 figures, 2 tables, submitted to PR
Ages and metallicities of stellar clusters using S-PLUS narrow-band integrated photometry: the Small Magellanic Cloud
The Magellanic Clouds are the most massive and closest satellite galaxies of
the Milky Way, with stars covering ages from a few Myr up to 13 Gyr. This makes
them important for validating integrated light methods to study stellar
populations and star-formation processes, which can be applied to more distant
galaxies. We characterized a set of stellar clusters in the Small Magellanic
Cloud (SMC), using the .
This is the first age (metallicity) determination for 11 (65) clusters of this
sample. Through its 7 narrow bands, centered on important spectral features,
and 5 broad bands, we can retrieve detailed information about stellar
populations. We obtained ages and metallicities for all stellar clusters using
the Bayesian spectral energy distribution fitting code .
With a sample of clusters in the color range , for which
our determined parameters are most reliable, we modeled the age-metallicity
relation of SMC. At any given age, the metallicities of SMC clusters are lower
than those of both the Gaia Sausage-Enceladus disrupted dwarf galaxy and the
Milky Way. In comparison with literature values, differences are
log(age) and [Fe/H], which is
comparable to low-resolution spectroscopy of individual stars. Finally, we
confirm a previously known gradient, with younger clusters in the center and
older ones preferentially located in the outermost regions. On the other hand,
we found no evidence of a significant metallicity gradient.Comment: 12 pages, 11 figure
A Non-parametric Approach to the D+ to K*0bar mu+ nu Form Factors
Using a large sample of D+ -> K- pi+ mu+ nu decays collected by the FOCUS
photoproduction experiment at Fermilab, we present the first measurements of
the helicity basis form factors free from the assumption of spectroscopic pole
dominance. We also present the first information on the form factor that
controls the s-wave interference discussed in a previous paper by the FOCUS
collaboration. We find reasonable agreement with the usual assumption of
spectroscopic pole dominance and measured form factor ratios.Comment: 14 pages, 5 figures, and 2 tables. We updated the previous version by
changing some words, removing one plot, and adding two tables. These changes
are mostly stylisti
Search for and Using Genetic Programming Event Selection
We apply a genetic programming technique to search for the double Cabibbo
suppressed decays and .
We normalize these decays to their Cabibbo favored partners and find
\Lambda_c^+ \to p K^+ \pi^-\Lambda_c^+ \to p K^-
\pi^+ and D_s^+ \to K^+ K^+
\pi^-D_s^+ \to K^+ K^- \pi^+ where
the first errors are statistical and the second are systematic. Expressed as
90% confidence levels (CL), we find and respectively.
This is the first successful use of genetic programming in a high energy
physics data analysis.Comment: 10 page
- …