2,201 research outputs found
Dynamical Masses of Low Mass Stars in the Taurus and Ophiuchus Star Forming Regions
We report new dynamical masses for 5 pre-main sequence (PMS) stars in the
L1495 region of the Taurus star-forming region (SFR) and 6 in the L1688 region
of the Ophiuchus SFR. Since these regions have VLBA parallaxes these are
absolute measurements of the stars' masses and are independent of their
effective temperatures and luminosities. Seven of the stars have masses
solar masses, thus providing data in a mass range with little data, and of
these, 6 are measured to precision . We find 8 stars with masses in the
range 0.09 to 1.1 solar mass that agree well with the current generation of PMS
evolutionary models. The ages of the stars we measured in the Taurus SFR are in
the range 1-3 MY, and MY for those in L1688. We also measured the
dynamical masses of 14 stars in the ALMA archival data for Akeson~\&~Jensen's
Cycle 0 project on binaries in the Taurus SFR. We find that the masses of 7 of
the targets are so large that they cannot be reconciled with reported values of
their luminosity and effective temperature. We suggest that these targets are
themselves binaries or triples.Comment: 20 page
Dynamical Masses of Young Stars in Multiple Systems
We present recent measurements of the orbital motion in the young binaries DF
Tau and ZZ Tau, and the hierarchical triple Elias 12, that were obtained with
the Fine Guidance Sensors on the HST and at the Keck Observatory using adaptive
optics. Combining these observations with previous measurements from the
literature, we compute preliminary orbital parameters for DF Tau and ZZ Tau. We
find that the orbital elements cannot yet be determined precisely because the
orbital coverage spans only about 90 degr in position angle. Nonetheless, the
range of possible values for the period and semi-major axis already defines a
useful estimate for the total mass in DF Tau and ZZ Tau, with values of
0.90{+0.85}{-0.35} M_sun and 0.81{+0.44}{-0.25} M_sun, respectively, at a
fiducial distance of 140 pc.Comment: 26 pages, 9 figures, accepted for publication in A
Preliminary Orbit of the Young Binary Haro 1-14c
Using the Keck Interferometer, we spatially resolved the orbit of the
pre-main sequence binary, Haro 1-14c, for the first time. We present these
interferometric observations along with additional spectroscopic radial
velocity measurements of the components. We performed a simultaneous orbit fit
to the interferometric visibilities and the radial velocities of Haro 1-14c.
Based on a statistical analysis of the possible orbital solutions that fit the
data, we determined component masses of M_1 = 0.96 (+0.27/-0.08) Msun and M_2 =
0.33 (+0.09/-0.02) Msun for the primary and secondary, respectively, and a
distance to the system of 111 (+19/-18) pc. The distance measurement is
consistent with the close distance estimates of the Ophiuchus molecular cloud.
Comparing our results with evolutionary tracks suggests an age of 3-4 Myr for
Haro 1-14c. With additional interferometric measurements to improve the
uncertainties in the masses and distance, we expect the low-mass secondary to
provide important empirical data for calibrating the theoretical evolutionary
tracks for pre-main sequence stars.Comment: 28 pages, 9 figures, accepted for publication in A
Avaliação de um teste de imunocromatografia para a detecção do vírus influenza A em suínos.
Projeto/Plano de Ação: 02.11.10600-02
Comparação entre dois sistemas biológicos para isolamento do vírus influenza a partir de amostras de pulmão e secreção nasal de suínos.
Projeto/Plano de Ação: 02.11.01.006
Comparação entre isolamento viral em ovos embrionados e em células MDCK do vírus Influenza A em suínos.
Projeto/Plano de Ação: 02.11.01.006
Perfil da infecção por vírus de influenza em suínos no Brasil após a introdução do vírus pandêmico H1N1 em 2009.
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