655 research outputs found
Abundances and kinematics for ten anticentre open clusters
Open clusters are distributed all across the disk and are convenient tracers
of its properties. In particular, outer disk clusters bear a key role for the
investigation of the chemical evolution of the Galactic disk. The goal of this
study is to derive homogeneous elemental abundances for a sample of ten outer
disk OCs, and investigate possible links with disk structures such as the
Galactic Anticenter Stellar Structure. We analyse high-resolution spectra of
red giants, obtained from the HIRES@Keck and UVES@VLT archives. We derive
elemental abundances and stellar atmosphere parameters by means of the
classical equivalent width method. We also performed orbit integrations using
proper motions. The Fe abundances we derive trace a shallow negative radial
metallicity gradient of slope -0.027+/-0.007 dex.kpc-1 in the outer 12 kpc of
the disk. The [alpha/Fe] gradient appears flat, with a slope of 0.006+/-0.007
dex.kpc-1 . The two outermost clusters (Be 29 and Sau 1) appear to follow
elliptical orbits. Be 20 also exhibits a peculiar orbit with a large excursion
above the plane. The irregular orbits of the three most metal-poor clusters (of
which two are located at the edge of the Galactic disk), if confirmed by more
robust astrometric measurements such as those of the Gaia mission, are
compatible with an inside-out formation scenario for the Milky Way, in which
extragalactic material is accreted onto the outer disk. We cannot determine if
Be 20, Be 29,and Sau 1 are of extragalactic origin, as they may be old genuine
Galactic clusters whose orbits were perturbed by accretion events or minor
mergers in the past 5 Gyr, or they may be representants of the thick disk
population. The nature of these objects is intriguing and deserves further
investigations in the near future.Comment: 17 pages, 9 figures; accepted for publication in A&
Asiago eclipsing binaries program. III. V570 Per
The orbit and physical parameters of the previously unsolved SB2 EB V570 Per
are derived using high resolution Asiago Echelle spectroscopy and B, V
photo-electric photometry. The metallicity from chi^2 analysis is [M/H]=+0.02
+/- 0.03, and reddening from interstellar NaI and KI absorption lines is E(B-V)
=0.023 +/- 0.007. The two components have masses of 1.449 +/- 0.006 and 1.350
+/- 0.006 Msun and spectral types F3 and F5, respectively. They are both still
within the Main Sequence band (T_1 =6842 +/- 25 K, T_2 =6562 +/- 25 K from
chi^2 analysis, R_1 =1.523 +/- 0.030, R_2 =1.388 +/- 0.019 Rsun) and are
dynamically relaxed to co-rotation with the orbital motion (Vrot sin i_{1,2}
=40 and 36 (+/-1) km/sec). The distance to V570 Per obtained from the orbital
solution is 123 +/- 2 pc, in excellent agreement with the revised Hipparcos
distance of 123 +/- 11 pc. The observed properties of V570 Per components are
compared to BaSTI models computed on purpose for exactly the observed masses
and varied chemical compositions. This system is interesting since both
components have their masses in the range where the efficiency of convective
core overshooting has to decrease with the total mass as a consequence of the
decreasing size of the convective core during the central H-burning stage. Our
numerical simulations show that, a small but not null overshooting is required,
with efficiencies lambda_{OV} =0.14 and 0.11 for the 1.449 and 1.350 Msun
components, respectively. This confirms the finding of Paper II on the similar
system V505 Per. At the approx 0.8 Gyr age of the system, the element diffusion
has reduced the surface metallicity of the models from the initial [M/H]=+0.17
to [M/H]=+0.02, in perfect agreement with the spectroscopically derived
[M/H]=+0.02 +/- 0.03 value.Comment: accepted by A&A. This revised upload to astro-ph correct a formatting
error generated by uncorrect A&A style fil
Through Silicon Vias in MEMS packaging, a review
Trough Silicon Via (TSV) is a key enabling technology to achieve the integration of various dies by exploiting the third dimension. This allow the integration of heterogeneous chips in a single package (2.5D integration) or to achieve higher integration densities of transistors (3D integration). These vertical interconnections are widely used for both IC and MEMS devices. This paper reviews TSV technology focusing on their implementation in MEMS sensors with a broad overview on the various fabrication approaches and their constraints in terms of process compatibility. A case study of an inertial MEMS sensor will then be presented.publishedVersio
Wafer bonding process for zero level vacuum packaging of MEMS
It is well known that the packaging of electronic devices is of paramount importance, none more so than in MEMS were fragile mechanical elements are realized. Among the different approaches, wafer to wafer bonding guarantees the advantages of the wafer scaling and provides protection of the devices during the final phase of fabrication. Direct bonding, also known as fusion bonding, is seldom implemented in MEMS fabrication due to the high surface quality required, the high temperature involved and the compulsory wet activation process. In this paper a direct bonding process for MEMS inertial sensor without the need of any wet activation step is presented.acceptedVersio
Wafer bonding process for zero level vacuum packaging of MEMS
It is well known that the packaging of electronic devices is of paramount importance, none more so than in MEMS were fragile mechanical elements are realized. Among the different approaches, wafer to wafer bonding guarantees the advantages of the wafer scaling and provides protection of the devices during the final phase of fabrication. Direct bonding, also known as fusion bonding, is seldom implemented in MEMS fabrication due to the high surface quality required, the high temperature involved and the compulsory wet activation process. In this paper a direct bonding process for MEMS inertial sensor without the need of any wet activation step is presented.acceptedVersio
The broad band spectral properties of galactic X-ray binary pulsars
BeppoSAX observed several galactic binary X-ray pulsars during the Science
Verification Phase and in the first year of the regular program. The complex
emission spectra of these sources are an ideal target for the BeppoSAX
instrumentation, that can measure the emission spectra in an unprecedented
broad energy band. Using this capability of BeppoSAX a detailed observational
work can be done on the galactic X-ray pulsars. In particular the 0.1-200 keV
energy band allows the shape of the continuum emission to be tightly
constrained. A better determination of the underlying continuum allows an
easier detection of features superimposed onto it, both at low energy (Fe K and
L, Ne lines) and at high energies (cyclotron features). We report on the
spectral properties of a sample of X-ray pulsars observed with BeppoSAX
comparing the obtained results. Some ideas of common properties are also
discussed and compared with our present understanding of the emission
mechanisms and processes.Comment: 6 pages, 2 figures. Uses espcrc2.sty (included).To appear in
Proceedings of "The Active X-ray Sky: Results from BeppoSAX and Rossi-XTE
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