Absolute dimensions of detached eclipsing binaries. I. The metallic-lined system WW Aurigae

WW Aurigae is a detached eclipsing binary composed of two metallic-lined A-type stars orbiting each other every 2.5 days. We have determined the masses and radii of both components to accuracies of 0.4 and 0.6 percent, respectively. From a cross-correlation analysis of high-resolution spectra we find masses of 1.964 +/- 0.007 Msun for the primary star and 1.814 +/- 0.007 Msun for the secondary star. From an analysis of photoelectric uvby and UBV light curves we find the radii of the stars to be 1.927 +/- 0.011 Rsun and 1.841 +/- 0.011 Rsun, where the uncertainties have been calculated using a Monte Carlo algorithm. Fundamental effective temperatures of the two stars have been derived, using the Hipparcos parallax of WW Aur and published ultraviolet, optical and infrared fluxes, and are 7960 +/- 420 and 7670 +/- 410 K. The masses, radii and effective temperatures of WW Aur are only matched by theoretical evolutionary models for a fractional initial metal abundance, Z, of approximately 0.06 and an age of roughly 90 Myr. This seems to be the highest metal abundance inferred for a well-studied detached eclipsing binary, but we find no evidence that it is related to the metallic-lined nature of the stars. The circular orbit of WW Aur is in conflict with the circularization timescales of both the Tassoul and the Zahn tidal theories and we suggest that this is due to pre-main-sequence evolution or the presence of a circular orbit when the stars were formed.Comment: Accepted for publication in MNRAS (14 pages, 8 figures). Photometric data will be made available at the CDS once the final version appear

High-precision photometry by telescope defocussing. III. The transiting planetary system WASP-2

We present high-precision photometry of three transits of the extrasolar planetary system WASP-2, obtained by defocussing the telescope, and achieving point-to-point scatters of between 0.42 and 0.73 mmag. These data are modelled using the JKTEBOP code, and taking into account the light from the recently-discovered faint star close to the system. The physical properties of the WASP-2 system are derived using tabulated predictions from five different sets of stellar evolutionary models, allowing both statistical and systematic errorbars to be specified. We find the mass and radius of the planet to be M_b = 0.847 +/- 0.038 +/- 0.024 Mjup and R_b = 1.044 +/- 0.029 +/- 0.015 Rjup. It has a low equilibrium temperature of 1280 +/- 21 K, in agreement with a recent finding that it does not have an atmospheric temperature inversion. The first of our transit datasets has a scatter of only 0.42 mmag with respect to the best-fitting light curve model, which to our knowledge is a record for ground-based observations of a transiting extrasolar planet.Comment: Accepted for publication in MNRAS. 9 pages, 3 figures, 10 table

Absolute dimensions of the unevolved B-type eclipsing binary GG Orionis

We present photometric observations in B and V as well as spectroscopic observations of the detached, eccentric 6.6-day double-lined eclipsing binary GG Ori, a member of the Orion OB1 association. Absolute dimensions of the components, which are virtually identical, are determined to high accuracy (better than 1% in the masses and better than 2% in the radii) for the purpose of testing various aspects of theoretical modeling. We obtain M(A) = 2.342 +/- 0.016 solar masses and R(A) = 1.852 +/- 0.025 solar radii for the primary, and M(B) = 2.338 +/- 0.017 solar masses and R(B) = 1.830 +/- 0.025 solar radii for the secondary. The effective temperature of both stars is 9950 +/- 200 K, corresponding to a spectral type of B9.5. GG Ori is very close to the ZAMS, and comparison with current stellar evolution models gives ages of 65-82 Myr or 7.7 Myr depending on whether the system is considered to be burning hydrogen on the main sequence or still in the final stages of pre-main sequence contraction. We have detected apsidal motion in the binary at a rate of dw/dt = 0.00061 +/- 0.00025 degrees per cycle, corresponding to an apsidal period of U = 10700 +/- 4500 yr. A substantial fraction of this (approximately 70%) is due to the contribution from General Relativity.Comment: To appear in The Astronomical Journal, December 200

On the nature of the right to resist: a rights-based theory of the ius resistendi in liberal democracies

Contesting the nature of right to resist continues to be of concern to those in power, for it poses the fundamental question about their legitimacy. From to Antigone to the Occupy Wall Street movement, individuals and communities have expressed their grievances and resisted oppression through a myriad of strategies. And although those taking the streets use the language of rights and appeal to a higher law to vindicate their claims, resistance has usually been considered a political, or rather, a security affair. The thesis vindicates the place of the ius resistendi in the normative order and uses legal probe to evince that there are no reasons why it could not be considered a legal right, except for political opportunity. The thesis challenges some basic postulates of liberal legal theories and develops a broader conception of rights, one in which reserved rights are part of a democratic normative system that performs in a manner consistent with its fundamental values. A primary, indeterminate right, the ius resistendi, I contend, embodies the Arendtian right to have rights.The Legitimacy and Effectiveness of Law & Governance in a World of Multilevel Jurisdiction

Eclipsing binaries in open clusters. III. V621 Per in chi Persei

V621 Persei is a detached eclipsing binary in the open cluster chi Persei which is composed of an early B-type giant star and a main sequence secondary component. From high-resolution spectroscopic observations and radial velocities from the literature, we determine the orbital period to be 25.5 days and the primary velocity semiamplitude to be K = 64.5 +/- 0.4 km/s. No trace of the secondary star has been found in the spectrum. We solve the discovery light curves of this totally-eclipsing binary and find that the surface gravity of the secondary star is log(g_B) = 4.244 +/- 0.054 (cm/s). We compare the absolute masses and radii of the two stars in the mass--radius diagram, for different possible values of the primary surface gravity, to the predictions of stellar models. We find that log(g_A) is approximately 3.55, in agreement with values found from fitting Balmer lines with synthetic profiles. The expected masses of the two stars are 12 Msun and 6 Msun, and the expected radii are 10 Rsun and 3 Rsun. The primary component is near the blue loop stage in its evolution.Comment: Accepted for publication in MNRAS (10 pages, 5 figures

Testing gravitational theories using Eccentric Eclipsing Detached Binaries

In this paper we compare the effects of different theories of gravitation on the apsidal motion of a sample of Eccentric Eclipsing Detached Binary stars. The comparison is performed by using the formalism of the Post-Newtonian parametrization to calculate the theoretical advance at periastron and compare it to the observed one, after having considered the effects of the structure and rotation of the involved stars. A variance analysis on the results of this comparison, shows that no significant difference can be found due to the effect of the different theories under test with respect to the standard General Relativity. It will be possible to observe differences, as we would expect, by checking the observed period variation on a much larger lapse of time. It can also be noticed from our results, that f(R) theory is the nearest to GR with respect to the other tested theories.Comment: 15 pages, 8 figures, 5 tables; Monthly Notices of the Royal Astronomical Society (2012) "Early View". arXiv admin note: text overlap with arXiv:gr-qc/0603071 by other author

The LMC eclipsing binary HV 2274: fundamental properties and comparison with evolutionary models

We are carrying out an international, multi-wavelength program to determine the fundamental properties and independent distance estimates of selected eclipsing binaries in the LMC and SMC. Eclipsing binaries with well-defined double-line radial velocity curves and light curves provide valuable information on orbital and physical properties of their component stars. The study of stars in the LMC and SMC where the metal abundances are significantly lower than solar provides an important opportunity to test stellar atmosphere, interior and evolution models, and opacities. For the first time, we can also measure direct M-L relations for stars outside our Galaxy. In this paper we concentrate on the determination of the orbital and physical properties of HV 2274 from analyses of light curves and new radial velocity curves formed from HST/GHRS observations. From UV/optical spectrophotometry of HV 2274 obtained with HST/FOS, the temperatures and the metallicity of the stars were found, as well as the interstellar extinction of the system. The values of mass, absolute radius, and effective temperature, for the primary and secondary stars are: 12.2(7) Mo, 9.9(2) Ro, 23000(180) K, and 11.4(7) Mo, 9.0(2) Ro, 23110(180) K, respectively. The age of the system (17(2) Myr), helium abundance (Y=0.26(3)) and a lower limit of the convective core overshooting parameter of 0.2 were obtained from fitting the stellar data with evolution models. The apsidal motion analysis corroborates that some amount of convective overshooting (0.2-0.5) is needed.Comment: 39 pages, 9 figures, accepted for publication in Ap

The Orbit and Occultations of KH 15D

The unusual flux variations of the pre-main-sequence binary star KH 15D have been attributed to occultations by a circumbinary disk. We test whether or not this theory is compatible with newly available data, including recent radial velocity measurements, CCD photometry over the past decade, and photographic photometry over the past 50 years. We find the model to be successful, after two refinements: a more realistic motion of the occulting feature, and a halo around each star that probably represents scattering by the disk. The occulting feature is exceptionally sharp-edged, raising the possibility that the dust in the disk has settled into a thin layer, and providing a tool for fine-scale mapping of the immediate environment of a T Tauri star. However, the window of opportunity is closing, as the currently visible star may be hidden at all orbital phases by as early as 2008.Comment: To appear in ApJ [16 pages, 13 figures

The Orbital Light Curve of Aquila X-1

We obtained R- and I-band CCD photometry of the soft X-ray transient/neutron- star binary Aql X-1 in 1998 June while it was at quiescence. We find that its light curve is dominated by ellipsoidal variations, although the ellipsoidal variations are severely distorted and have unequal maxima. After we correct for the contaminating flux from a field star located only 0.46" away, the peak-to-peak amplitude of the modulation is ~0.25 mag in the R band, which requires the orbital inclination to be greater than 36 degrees. The orbital period we measure is consistent with the 18.95 h period measured by Chevalier & Ilovaisky (1998). During its outbursts the light curve of Aql X-1 becomes single humped. The outburst light curve observed by Garcia et al. (1999) agrees in phase with our quiescent light curve. We show that the single humped variation is caused by a ``reflection effect,'' that is, by heating of the side of the secondary star facing towards the neutron star.Comment: 18 manuscript pages, 7 figures; accepted by A