1,915 research outputs found
Evaluating GAIA performances on eclipsing binaries. I. Orbits and stellar parameters for V505 Per, V570 Per and OO Peg
The orbits and physical parameters of three detached, double-lined A-F
eclipsing binaries have been derived combining H_P, V_T, B_T photometry from
the Hipparcos/Tycho mission with 8500-8750 Ang ground-based spectroscopy,
mimicking the photometric+spectroscopic observations that should be obtained by
GAIA, the approved Cornerstone 6 mission by ESA. This study has two main
objectives, namely (a) to derive reasonable orbits for a number of new
eclipsing binaries and (b) to evaluate the expected performances by GAIA on
eclipsing binaries and the accuracy achievable on the determination of
fundamental stellar parameters like masses and radii. It is shown that a 1%
precision in the basic stellar parameters can be achieved by GAIA on well
observed detached eclipsing binaries provided that the spectroscopic
observations are performed at high enough resolution. Other types of eclipsing
binaries (including semi-detached and contact types) and different spectral
types will be investigated in following papers along this series.Comment: A&A, 11 pages, 5 figures, 5 table
The narrow and moving HeII lines in nova KT Eri
We present outburst and quiescence spectra of the classical nova KT Eri and
discuss the appearance of a sharp HeII 4686 Ang emission line, whose origin is
a matter of discussion for those novae that showed a similar component. We
suggest that the sharp HeII line, when it first appeared toward the end of the
outburst optically thick phase, comes from the wrist of the dumbbell structure
characterizing the ejecta as modeled by Ribeiro et al. (2013). When the ejecta
turned optically thin, the already sharp HeII line became two times narrower
and originated from the exposed central binary. During the optically thin
phase, the HeII line displayed a large change in radial velocity that had no
counterpart in the Balmer lines (both their narrow cores and the broad
pedestals). The large variability in radial velocity of the HeII line continued
well into quiescence, and it remains the strongest emission line observed over
the whole optical range.Comment: in press in A&
Asiago eclipsing binaries program. I. V432 Aur
The orbit and physical parameters of the previously unsolved eclipsing binary
V432 Aur, discovered by Hipparcos, have been derived with errors better than 1%
from extensive Echelle spectroscopy and B, V photometry. Synthetic spectral
analysis of both components has been performed, yielding T_eff and log g in
close agreement with the orbital solution, a metallicity [Z/Z_sun]=-0.60 and
rotational synchronization for both components. Direct comparison on the
theoretical L, T_eff plane with the Padova evolutionary tracks and isochrones
for the masses of the two components (1.22 and 1.08 M_sun) provides a perfect
match and a 3.75 Gyr age. The more massive and cooler component is approaching
the base of the giant branch and displays a probable pulsation activity with an
amplitude of Delta V = 0.075 mag and Delta rad.vel. = 1.5 km/sec. With a T_eff
= 6080 K it falls to the red of the nearby instability strip populated by delta
Sct and gamma Dor types of pulsating variables. Orbital modeling reveals a
large and bright surface spot on it. The pulsations activity and the large
spot(s) suggest the presence of macro-turbulent motions in its atmosphere. They
reflect in a line broadening that at cursory inspection could be taken as
indication of a rotation faster than synchronization, something obviously odd
for an old, expanding star.Comment: A&A, 11 pages, accepted Jan 7, 200
ISM studies of GRB 030329 with high resolution spectroscopy
We present a series of early UVES/VLT high resolution spectra of the
afterglow of GRB 030329 at redshift z=0.16867+-0.00001. In contrast to other
spectra from this burst, both emission and absorption lines were detected. None
of them showed any temporal evolution. From the emission lines, we determine
the properties of the host galaxy which has a star formation rate (SFR) of
0.198 M_solar yr^-1 and a low metallicity of 1/7 Z_solar. Given the low total
stellar host mass M_star=10^7.75+-0.15 M_solar and an absolute luminosity
m_V=-16.37, we derive specific SFRs (SSFR) of log SFR/M = -8.5 yr^-1 and SFR/L
= 14.1 M_solar yr^-1 L_*^-1. This fits well into the picture of GRB hosts as
being low mass, low metallicity, actively star forming galaxies. The MgII and
MgI absorption lines from the host show multiple narrow (Doppler width b=5-10
km/s) components spanning a range of v about 260 km/s, mainly blueshifted
compared to the redshift from the emission lines. These components are likely
probing outflowing material of the host galaxy, which could arise from former
galactic superwinds, driven by supernovae from star forming regions. Similar
features have been observed in QSO spectra. The outflowing material is mainly
neutral with high column densities of log N(MgII)=14.0+-0.1 cm^-2 and log
N(MgI)=12.3+-0.1 cm^-2.Comment: 11 pages, 4 figures, submitted to Ap
The secondary minimum in YY Her: Evidence for a tidally distorted giant
We present and analyze quiescent UBVRI light curves of the classical
symbiotic binary YY Her. We show that the secondary minimum, which is clearly
visible only in the quiescent VRI light curves, is due to ellipsoidal
variability of the red giant component. Our simple light curve analysis, by
fitting of the Fourier cosine series, resulted in a self-consistent
phenomenological model of YY Her, in which the periodic changes can be
described by a combination of the ellipsoidal changes and a sinusoidal changes
of the nebular continuum and line emission.Comment: 5 pages, 2 figures, to appear in Astronomy & Astrophysic
First Results for the Solar Neighborhood of the Asiago Red Clump Survey
The Asiago Red Clump Spectroscopic Survey (ARCS) is an ongoing survey that
provides atmospheric parameters, distances and space velocities of a well
selected sample of Red Clump stars distributed along the celestial equator. We
used the ARCS catalog for a preliminary investigation of the Galactic disk in
the Solar Neighborhood, in particular we focused on detection and
characterization of moving groups.Comment: 2 pages, 1 figure, to appear in the proceedings of "Assembling the
Puzzle of the Milky Way", Le Grand Bornand (April 17-22, 2011), C. Reyle, A.
Robin, M. Schultheis (eds.
Litigation risks and firms innovation dynamics after the IPO
An initial public offering (IPO) is a critical event in a firm’s life cycle which can reshape its innovation strategy. Research suggests that after going public firms experience an increase in patent productivity. Our paper explores perceived litigation risks as a determinant of this outcome by examining US semiconductor firms. Results show that perceived patent litigation risks are positively associated with patent productivity after the IPO. Interestingly, we also find that the amount of capital raised during the IPO is positively associated with patent productivity after the IPO, successfully replicating previous findings on this relationship. These results are robust to model specifications where we attempt to account for the dynamics of self-selection of firms into IPO by considering matched control firms with similar pre-IPO characteristics, but that never went public
Evaluating GAIA performances on eclipsing binaries. III. Orbits and stellar parameters for UW LMi, V432 Aur and CN Lyn
The orbits and physical parameters of three detached F and G-type eclipsing
binaries have been derived combining Hipparcos H(P) photometry with 8480-8740
Ang ground-based spectroscopy, simulating the photometric+spectroscopic
observations that the GAIA mission will obtain. Tycho B(T) and V(T) light
curves are too noisy to be modeled for the three targets, and only mean Tycho
colors are retained to constrain the temperature. No previous combined
photometric+spectroscopic solution exists in literature for any of the three
targets. Quite remarkably, CN Lyn turned out to be an equal masses F5 triple
system. Distances from the orbital solutions agree within the astrometric error
with the Hipparcos parallaxes.Comment: A&A, accepted in pres
Spectrum Analysis of the Type Ib Supernova 1999dn: Probable Identifications of C II and H-alpha
Low resolution spectra of SN 1999dn at early times are presented and compared
with synthetic spectra generated with the parameterized supernova
synthetic-spectrum code SYNOW. We find that the spectra of SN 1999dn strongly
resemble those of SN 1997X and SN 1984L, and hence we classify it as a Type Ib
event. Line-identifications are established through spectrum synthesis. Strong
evidence of both H-alpha and C II 6580 is found. We infer that H-alpha appears
first, before the time of maximum brightness, and then is blended with and
finally overwhelmed by the C II line after maximum; this favors a thin
high-velocity hydrogen skin in this Type Ib supernova.Comment: 15 pages, 3 figures. Accepted for publication in Ap
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