7 research outputs found
Radial Velocity Studies of Close Binary Stars.VI
Radial-velocity measurements and sine-curve fits to the orbital velocity
variations are presented for the sixth set of ten close binary systems: SV Cam,
EE Cet, KR Com, V410 Cyg, GM Dra, V972 Her, ET Leo, FS Leo, V2388 Oph, II UMa.
All systems except FS Leo are double-lined spectroscopic binaries. The type of
FS Leo is unknown while SV Cam is a close, detached binary; all remaining
systems are contact binaries. Eight binaries (all except SV Cam and V401 Cyg)
are the recent photometric discoveries of the Hipparcos satellite project. Five
systems, EE Cet, KR Com, V401 Cyg, V2388 Oph, II UMa, are members of
visual/spectroscopic triple systems. We were able to observe the close binary
system EE Cet separately of its companion, but in the remaining four systems we
could separate the spectral components only through the use of the
broadening-function approach. Several of the studied systems are prime
candidates for combined light and radial-velocity synthesis solutions.Comment: AASTeX5, 5 figures, 2 tables, modified after the AJ revie
The 7.5 Magnitude Limit Sample of Bright Short-Period Binary Stars. I. How Many Contact Binaries Are There?
A sample of bright contact binary stars (W UMa-type or EW, and related: with
beta Lyr light curves, EB, and ellipsoidal, ELL - in effect, all but the
detached, EA), to the limit of Vmax = 7.5 magnitude is deemed to include all
discoverable short-period (P<1 days) binaries with photometric variation larger
than about 0.05 magnitude. Of the 32 systems in the final sample, 11 systems
have been discovered by the Hipparcos satellite. The combined spatial density
is evaluated at (1.02+/-0.24)x10^-5 pc^-3. The Relative Frequency of Occurrence
(RFO), defined in relation to the Main Sequence stars, depends on the
luminosity. An assumption of RFO~1/500 for MV>+1.5 is consistent with the data,
although the number statistics is poor with the resulting uncertainty in the
spatial density and the RFO by a factor of about two. The RFO rapidly decreases
for brighter binaries to a level of 1/5,000 for MV<+1.5 and to 1/30,000 for
MV<+0.5. The high RFO of 1/130, previously determined from the deep OGLE-I
sample of Disk Population W UMa-type systems towards Baade's Window, is
inconsistent with and unconfirmed by the new results. Possible reasons for the
large discrepancy are discussed. They include several observational effects,
but also a possibility of a genuine increase in the contact-binary density in
the central parts of the Galaxy.Comment: AASTeX5, 11 figures, 3 tables. Table 1 is very wide; in case of
problems send e-mail to [email protected] for a raw text versio
Evolutionary status and chemical composition of the atmosphere of the spectroscopic and speckle interferometric binary HD 10009
Deriving static atomic multipoles from the electrostatic potential
The description of molecular systems using multipolar electrostatics calls for automated methods to fit the necessary parameters. In this paper, we describe an open-source software package that allows fitting atomic multipoles (MTPs) from the ab initio electrostatic potential by adequate atom typing and judicious assignment of the local axis system. By enabling the simultaneous fit of several molecules and/or conformations, the package addresses issues of parameter transferability and lack of sampling for buried atoms. We illustrate the method by studying a series of small alcohol molecules, as well as various conformations of protonated butylamine
Geometry Optimization in Polarizable QM/MM Models: The Induced Dipole Formulation
We present the mathematical derivation and the computational implementation of the analytical geometry derivatives for a polarizable QM/MM model (QM/MMPol). In the adopted QM/MMPol model, the focused part is treated at QM level of theory, while the remaining part (the environment) is described classically as a set of fixed charges and induced dipoles. The implementation is performed within the ONIOM procedure, resulting in a polarizable embedding scheme, which can be applied to solvated and embedded systems and combined with different polarizable force fields available in the literature. Two test cases characterized by strong hydrogen-bond and dipole−dipole interactions, respectively, are used to validate the method with respect to the nonpolarizable one. Finally, an application to geometry optimization of the chromophore of Rhodopsin is presented to investigate the impact of including mutual polarization between the QM and the classical parts in conjugated systems