2,029 research outputs found
SIPLIC forms of hourly precipitation data - Casper, Cheyenne, Lander, Sheridan, 1949-1951
Hourly precipitation data from four weather stations over a 13-year period presented in SIPLIC form with aid of IBM 1620 compute
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
Lithium in the Symbiotic Mira V407 Cyg
We report an identification of the lithium resonance doublet LiI 6708A in the
spectrum of V407 Cyg, a symbiotic Mira with a pulsation period of about 745
days. The resolution of the spectra used was R~18500 and the measured
equivalent width of the line is ~0.34A. It is suggested that the lithium
enrichment is due to hot bottom burning in the intermediate mass AGB variable,
although other possible origins cannot be totally ruled out. In contrast to
lithium-rich AGB stars in the Magellanic clouds, ZrO 5551A, 6474A absorption
bands were not found in the spectrum of V407Cyg. These are the bands used to
classify the S-type stars at low-resolution. Although we identified weak ZrO
5718A, 6412A these are not visible in the low-resolution spectra, and we
therefore classify the Mira in V407 Cyg as an M type. This, together with other
published work, suggests lithium enrichment can precede the third dredge up of
s-process enriched material in galactic AGB stars.Comment: 4 pages, 2 figures, to be published in MNRA
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
Kinematics and binaries in young stellar aggregates. II. NGC 6913 = M29
Between 1996 and 2003 we have obtained 226 high resolution spectra of 16
stars in the field of the young open cluster NGC 6913, to the aim of
constraining its main properties and study its internal kinematics. Twelve of
the program stars turned out to be members, one of them probably unbound. Nine
are binaries (one eclipsing and another double lined) and for seven of them the
observations allowed to derive the orbital elements. All but two of the nine
discovered binaries are cluster members. In spite of the young age (a few Myr),
the cluster already shows signs that could be interpreted as evidence of
dynamical relaxation and mass segregation. However, they may be also the result
of an unconventional formation scenario. The dynamical (virial) mass as
estimated from the radial velocity dispersion is larger than the cluster
luminous mass, which may be explained by a combination of the optically thick
interstellar cloud that occults part of the cluster, the unbound state or
undetected very wide binary orbit of some of the members that inflate the
velocity dispersion and a high inclination for the axis of a possible cluster
angular momentum. All discovered binaries are hard enough to survive average
close encounters within the cluster and do not yet show sign of relaxation of
the orbital elements to values typical of field binaries.Comment: Astron.Astrophys. submitted, 8 figures, 7 tables, 12 pages. Figures 1
and 6 degraded in quality with respect to originals to save file dimension
Numerical simulations challenged on the prediction of massive subhalo abundance in galaxy clusters: the case of Abell 2142
In this Letter we compare the abundance of member galaxies of a rich, nearby
() galaxy cluster, Abell 2142, with that of halos of comparable virial
mass extracted from sets of state-of-the-art numerical simulations, both
collisionless at different resolutions and with the inclusion of baryonic
physics in the form of cooling, star formation, and feedback by active galactic
nuclei. We also use two semi-analytical models to account for the presence of
orphan galaxies. The photometric and spectroscopic information, taken from the
Sloan Digital Sky Survey Data Release 12 (SDSS DR12) database, allows us to
estimate the stellar velocity dispersion of member galaxies of Abell 2142. This
quantity is used as proxy for the total mass of secure cluster members and is
properly compared with that of subhalos in simulations. We find that simulated
halos have a statistically significant ( sigma confidence level)
smaller amount of massive (circular velocity above )
subhalos, even before accounting for the possible incompleteness of
observations. These results corroborate the findings from a recent strong
lensing study of the Hubble Frontier Fields galaxy cluster MACS J0416
\citep{grillo2015} and suggest that the observed difference is already present
at the level of dark matter (DM) subhalos and is not solved by introducing
baryonic physics. A deeper understanding of this discrepancy between
observations and simulations will provide valuable insights into the impact of
the physical properties of DM particles and the effect of baryons on the
formation and evolution of cosmological structures.Comment: 8 pages, 2 figures. Modified to match the version published in ApJ
NGC 6738: not a real open cluster
A photometric, astrometric and spectroscopic investigation of the poorly
studied open cluster NGC 6738 has been performed in order to ascertain its real
nature. NGC 6738 is definitely not a physical stellar ensemble: photometry does
not show a defined mean sequence, proper motions and radial velocities are
randomly distributed, spectro-photometric parallaxes range between 10 and 1600
pc, and the apparent luminosity function is identical to that of the
surrounding field. NGC 6738 therefore appears to be an apparent concentration
of a few bright stars projected on patchy background absorption.Comment: A&A, in press (compared with first submission to astro-ph, now Table
2 and Figure 4 are replaced with corrected versions
Memory effect in melting behaviour, crystallization kinetics and morphology of poly(propylene terephthalate)
Crystallization kinetics and melting behaviour of poly(propylene terephthalate) (PPT) were investigated by means of differential scanning calorimetry and hot-stage optical microscopy. Isothermal crystallization kinetics was analysed according to the Avrami treatment. The effects of temperature and duration of melting on the overall rate of isothermal crystallization were studied: the rate was found to decrease with increasing melting temperature and melting time. This result was discussed on the basis of the gradual destruction of predetermined athermal nuclei. Values of the Avrami exponent close to 3 were obtained, regardless of the adopted thermal treatment and the crystallization temperature, Tc, in agreement with a crystallization process originating from predetermined nuclei and characterized by three-dimensional spherulitic growth. As a matter of fact, spacefilling spherulites were observed by optical microscopy at all Tc's, independent of the applied thermal treatments. For each of them, the rate of crystallization became lower as Tc increased, as usual at low undercooling where the crystallization process is controlled by nucleation. The observed multiple endotherms, which are commonly displayed by polyesters, were influenced by Tc and ascribed to melting and recrystallization processes. Linear and non-linear treatments were applied in order to estimate the equilibrium melting temperature for PPT, by using the corrected melting temperatures. The non-linear estimation yielded an about 33°C higher value with respect to the one obtained by means of the linear approach. Through the analysis of secondary nucleation theory, the classical II→III transition was found to occur at a temperature of 194°C. The average work of chain folding for nucleation was determined to be c. 5.2 kcal/mol. The heat of fusion was correlated to the specific heat increment for samples with different degree of crystallinity and the results were interpreted on the basis of the existence of an interphase, whose amount was found to depend on the thermal treatment the polymer was subjected to
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