1,169 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
V496 Scuti: An Fe II nova with dust shell accompanied by CO emission
We present near-infrared and optical observations of the nova V496 Scuti 2009
covering various phases - pre-maximum, early decline and nebular - during the
first 10 months of its discovery followed by limited observations in early part
of 2011 April. The spectra follow the evolution of the nova when the lines had
strong P Cygni profiles to a phase dominated by prominent emission lines. The
notable feature of the near-IR spectra in the early decline phase is the rare
presence of first overtone bands of carbon monoxide in emission. Later about
150 days after the peak brightness the IR spectra show clear dust formation in
the expanding ejecta. Dust formation in V496 Sct is consistent with the
presence of lines of elements with low ionization potentials like Na and Mg in
the early spectra and the detection of CO bands in emission. The light curve
shows a slow rise to the maximum and a slow decline indicating a prolonged mass
loss. This is corroborated by the strengthening of P Cygni profiles during the
first 30 days. In the spectra taken close to the optical maximum brightness,
the broad and single absorption component seen at the time of discovery is
replaced by two sharper components. During the early decline phase two sharp
dips that show increasing outflow velocities are seen in the P Cygni absorption
components of Fe II and H I lines. The spectra in 2010 March showed the onset
of the nebular phase. Several emission lines display saddle-like profiles
during the nebular phase. In the nebular stage the observed fluxes of [O III]
and H-beta lines are used to estimate the electron number densities and the
mass of the ejecta. The optical spectra show that the nova evolved in the P_fe
A_o spectral sequence. The physical conditions in the ejecta are estimated. The
absolute magnitude and the distance to the nova are estimated to be M_V = -7.0
+/- 0.2 and d = 2.9 +/- 0.3 kpc respectively.Comment: 14 pages, 9 figures and 6 Tables, Accepted for Publication in MNRA
The 2010 nova outburst of the symbiotic Mira V407 Cyg
The nova outburst experienced in 2010 by the symbiotic binary Mira V407 Cyg
has been extensively studied at optical and infrared wavelengths with both
photometric and spectroscopic observations. This outburst, reminiscent of
similar events displayed by RS Oph, can be described as a very fast He/N nova
erupting while being deeply embedded in the dense wind of its cool giant
companion. The hard radiation from the initial thermonuclear flash ionizes and
excites the wind of the Mira over great distances (recombination is observed on
a time scale of 4 days). The nova ejecta is found to progressively decelerate
with time as it expands into the Mira wind. This is deduced from line widths
which change from a FWHM of 2760 km/s on day +2.3 to 200 km/s on day +196. The
wind of the Mira is massive and extended enough for an outer neutral and
unperturbed region to survive at all outburst phases.Comment: MNRAS Letter, in pres
Continuous stellate ganglion block in delayed cerebral ischemia: A possible supplementary approach to traditional therapy?
Delayed Cerebral Ischemia (DCI) is a major contributor to morbidity and mortality after SAH. Currently the prevention of vasospasm and DCI relies on nimodipine administration and on maintaining an adequate cerebral perfusion pressure. We report a patient with initial DCI after SAH in which stellate ganglion block (SGB) was performed after nimodipine administration. Firstly the procedure was characterized by a iv and intra-arterial nimodipine administration which did not result into a normal perfusion pattern. Therefore a single-shot stellate ganglion block was performed, as suggested in literature. Because of the not sufficient but promising perfusion improvement, we decided to deliver a continuous ganglion block (cSGB) for 5 days. Consequently a further improvement of the cerebral perfusion on CTPerfusion and Real Time Angiographic Perfusion Assessment was registered. In order to treat cerebral vasospasm, SGB is known to be a further valuable treatment, despite its temporary effect. However the continuous use of SGB during initial DCI has never been described before
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
Photometric and spectroscopic variability of the FUor star V582 Aurigae
We carried out BVRI CCD photometric observations in the field of V582 Aur
from 2009 August to 2013 February. We acquired high-, medium-, and
low-resolution spectroscopy of V582 Aur during this period. To study the
pre-outburst variability of the target and construct its historical light
curve, we searched for archival observations in photographic plate collections.
Both CCD and photographic observations were analyzed using a sequence of 14
stars in the field of V582 Aur calibrated in BVRI. The pre-outburst
photographic observations of V582 Aur show low-amplitude light variations
typical of T Tauri stars. Archival photographic observations indicate that the
increase in brightness began in late 1984 or early 1985 and the star reached
the maximum level of brightness at 1986 January. The spectral type of V582 Aur
can be defined as G0I with strong P Cyg profiles of H alpha and Na I D lines,
which are typical of FU Orionis objects. Our BVRI photometric observations show
large amplitude variations V~2.8 mag. during the 3.5 year period of
observations. Most of the time, however, the star remains in a state close to
the maximum brightness. The deepest drop in brightness was observed in the
spring of 2012, when the brightness of the star fell to a level close to the
pre-outburst. The multicolor photometric data show a color reversal during the
minimum in brightness, which is typical of UX Ori variables. The corresponding
spectral observations show strong variability in the profiles and intensities
of the spectral lines (especially H alpha), which indicate significant changes
in the accretion rate. On the basis of photometric monitoring performed over
the past three years, the spectral properties of the maximal light, and the
shape of the long-term light curve, we confirm the affiliation of V582 Aur to
the group of FU Orionis objects.Comment: 9 pages, 8 figures, accepted for publication in A&
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