1,823 research outputs found
Early-type stars in the young open cluster IC1805. II. The probably single stars HD15570 and HD15629, and the massive binary/triple system HD15558
Aims: We address the issue of the multiplicity of the three brightest
early-type stars of the young open cluster IC1805, namely HD15570, HD15629 and
HD15558. Methods: For the three stars, we measured the radial velocity by
fitting Gaussian curves to line profiles in the optical domain. In the case of
the massive binary HD15558, we also used a spectral disentangling method to
separate the spectra of the primary and of the secondary in order to derive the
radial velocities of the two components. These measurements were used to
compute orbital solutions for HD15558. Results: For HD15570 and HD15629, the
radial velocities do not present any significant trend attributable to a binary
motion on time scales of a few days, nor from one year to the next. In the case
of HD15558 we obtained an improved SB1 orbital solution with a period of about
442 days, and we report for the first time on the detection of the spectral
signature of its secondary star. We derive spectral types O5.5III(f) and O7V
for the primary and the secondary of HD15558. We tentatively compute a first
SB2 orbital solution although the radial velocities from the secondary star
should be considered with caution. The mass ratio is rather high, i.e. about 3,
and leads to very extreme minimum masses, in particular for the primary object.
Minimum masses of the order of 150 \pm 50 and 50 \pm 15 M_\odot are found
respectively for the primary and the secondary. Conclusions: We propose that
HD15558 could be a triple system. This scenario could help to reconcile the
very large minimum mass derived for the primary object with its spectral type.
In addition, considering new and previously published results, we find that the
binary frequency among O-stars in IC1805 has a lower limit of 20%, and that
previously published values (80%) are probably overestimated.Comment: 12 pages, including 6 figures (+ 4 pages of online material),
accepted for publication by A&
Disentanglement by Dissipative Open System Dynamics
This paper investigates disentanglement as a result of evolution according to
a class of master equations which include dissipation and interparticle
interactions. Generalizing an earlier result of Di\'{o}si, the time taken for
complete disentanglement is calculated (i.e. for disentanglement from any other
system). The dynamics of two harmonically coupled oscillators is solved in
order to study the competing effects of environmental noise and interparticle
coupling on disentanglement. An argument based on separability conditions for
gaussian states is used to arrive at a set of conditions on the couplings
sufficient for all initial states to disentangle for good after a finite time.Comment: Paper in conjunction with and following on from P.J. Dodd and J.J.
Halliwell: quant-ph/031206
A new investigation of the binary HD 48099
With an orbital period of about 3.078 days, the double-lined spectroscopic
binary HD 48099 is, still now, the only short-period O+O system known in the
Mon OB2 association. Even though an orbital solution has already been derived
for this system, few information are available about the individual stars. We
present, in this paper, the results of a long-term spectroscopic campaign. We
derive a new orbital solution and apply a disentangling method to recover the
mean spectrum of each star. To improve our knowledge concerning both
components, we determine their spectral classifications and their projected
rotational velocities. We also constrain the main stellar parameters of both
stars by using the CMFGEN atmosphere code and provide the wind properties for
the primary star through the study of IUE spectra. This investigation reveals
that HD 48099 is an O5.5 V((f))+O9 V binary with M_1 sin^3 i = 0.70 M_{\sun}
and M_2 sin^3 i = 0.39 M_{\sun}, implying a rather low orbital inclination.
This result, combined with both a large effective temperature and log g,
suggests that the primary star (v sini ~ 91 km s^-1) is actually a fast rotator
with a strongly clumped wind and a nitrogen abundance of about 8 times the
solar value.Comment: 12 pages, 7 figures, accepted by Ap
Mesoscopic superpositions of states - approach to classicality and diagonalization in coherent state basis
I consider the interaction of a superposition of mesoscopic coherent states
and its approach to a mixed state as a result of a suitably controlled
environment. I show how the presence of a gain medium in a cavity can lead to
diagonalization in coherent state basis in contrast to the standard model of
decoherence. I further show how the new model of decoherence can lead to the
generation of ordered quasi distributions.Comment: 10 pages, two figure pages, RevTe
Optical spectroscopy of X-Mega targets in the Carina nebula - VII On the multiplicity of Tr 16-112, HD 93343 and HD 93250
We present the results of a spectroscopic monitoring campaign devoted to
three O-type stars in the Carina nebula. We derive the full SB2 orbital
solution of the binary system Tr 16-112, an exceptional dissymmetrical system
consisting of an O5.5-6V((f?p)) primary and a B2V-III secondary. We also
report on low-amplitude brightness variations in Tr 16-112 that are likely due
to the ellipsoidal shape of the O5.5-6 primary revolving in an eccentric orbit
around the system's centre of mass. We detect for the first time a clear SB2
binary signature in the spectrum of HD 93343 (O8 + O8), although our data are
not sufficient to establish an orbital solution. This system also displays low
amplitude photometric modulations. On the other hand, no indication of
multiplicity is found in the optical spectra of HD 93250. Finally, we discuss
the general properties of multiple massive stars in the Carina OB1 association.Comment: Accepted for publication in MNRA
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