2,928 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
Properties, evolution and morpho-kinematical modelling of the very fast nova V2672 Oph (Nova Oph 2009), a clone of U Sco
V2672 Oph reached maximum brightness V=11.35 on 2009 August 16.5. With
observed t2(V)=2.3 and t3(V)=4.2 days decline times, it is one of the fastest
known novae, being rivalled only by V1500 Cyg (1975) and V838 Her (1991) among
classical novae, and U Sco among the recurrent ones. The line of sight to the
nova passes within a few degrees of the Galactic centre. The reddening of V2672
Oph is E(B-V)=1.6 +/-0.1, and its distance ~19 kpc places it on the other side
of the Galactic centre at a galacto-centric distance larger than the solar one.
The lack of an infrared counterpart for the progenitor excludes the donor star
from being a cool giant like in RS Oph or T CrB. With close similarity to U
Sco, V2672 Oph displayed a photometric plateau phase, a He/N spectrum
classification, extreme expansion velocities and triple peaked emission line
profiles during advanced decline. The full width at zero intensity of Halpha
was 12,000 km/s at maximum, and declined linearly in time with a slope very
similar to that observed in U Sco. We infer a WD mass close to the
Chandrasekhar limit and a possible final fate as a SNIa. Morpho-kinematical
modelling of the evolution of the Halpha profile suggests that the overall
structure of the ejecta is that of a prolate system with polar blobs and an
equatorial ring. The density in the prolate system appeared to decline faster
than that in the other components. V2672 Oph is seen pole-on, with an
inclination of 0+/-6 deg and an expansion velocity of the polar blobs of 4800
+900/-800 km/s. On the basis of its remarkable similarity to U Sco, we suspect
this nova may be a recurrent. Given the southern declination, the faintness at
maximum, the extremely rapid decline and its close proximity to the Ecliptic,
it is quite possible that previous outbursts of V2672 Oph have been missed.Comment: in press in MNRA
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
Distance and Reddening of the Enigmatic Gamma-ray-Detected Nova V1324 Sco
It has recently been discovered that some, if not all, classical novae emit
GeV gamma-rays during outburst. Despite using an unreliable method to determine
its distance, previous work showed that nova V1324 Sco was the most gamma-ray
luminous of all gamma-ray-detected novae. We present here a different, more
robust, method to determine the reddening and distance to V1324 Sco using
high-resolution optical spectroscopy. Using two independent methods we derived
a reddening of E(B-V) = 1.16 +/- 0.12 and a distance rD > 6.5 kpc. This
distance is >40% greater than previously estimated, meaning that V1324 Sco has
an even higher gamma-ray luminosity than previously calculated. We also use
periodic modulations in the brightness, interpreted as the orbital period, in
conjunction with pre-outburst photometric limits to show that a main-sequence
companion is strongly favored.Comment: Submitted to ApJ. 6 pages, 5 figure
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
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
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