The Rossiter-McLaughlin effect reloaded: Probing the 3D spin-orbit geometry, differential stellar rotation, and the spatially-resolved stellar spectrum of star-planet systems

When a planet transits its host star, it blocks regions of the stellar surface from view; this causes a distortion of the spectral lines and a change in the line-of-sight (LOS) velocities, known as the Rossiter-McLaughlin (RM) effect. Since the LOS velocities depend, in part, on the stellar rotation, the RM waveform is sensitive to the star-planet alignment (which provides information on the system’s dynamical history). We present a new RM modelling technique that directly measures the spatially-resolved stellar spectrum behind the planet. This is done by scaling the continuum flux of the (HARPS) spectra by the transit light curve, and then subtracting the infrom the out-of-transit spectra to isolate the starlight behind the planet. This technique does not assume any shape for the intrinsic local profiles. In it, we also allow for differential stellar rotation and centre-to-limb variations in the convective blueshift. We apply this technique to HD 189733 and compare to 3D magnetohydrodynamic (MHD) simulations. We reject rigid body rotation with high confidence (>99% probability), which allows us to determine the occulted stellar latitudes and measure the stellar inclination. In turn, we determine both the sky-projected (λ ≈ −0.4 ± 0.2◦) and true 3D obliquity (ψ ≈ 7+12 −4 ◦ ). We also find good agreement with the MHD simulations, with no significant centre-to-limb variations detectable in the local profiles. Hence, this technique provides a new powerful tool that can probe stellar photospheres, differential rotation, determine 3D obliquities, and remove sky-projection biases in planet migration theories. This technique can be implemented with existing instrumentation, but will become even more powerful with the next generation of high-precision radial velocity spectrographs.

Ultraviolet emission lines of Si II in cool star and solar spectra

Recent atomic physics calculations for Si II are employed within the CLOUDY modelling code to analyse Hubble Space Telescope (HST) STIS ultraviolet spectra of three cool stars, β Geminorum, α Centauri A and B, as well as previously published HST/GHRS observations of α Tau, plus solar quiet Sun data from the High Resolution Telescope and Spectrograph. Discrepancies found previously between theory and observation for line intensity ratios involving the 3s²3p ²PJ-3s3p^{2 4}P^J' intercombination multiplet of Si II at ~ 2335 Å are significantly reduced, as are those for ratios containing the 3s²3p ²PJ-3s3p^{2 2}DJ ~ transitions at ~1816 Å. This is primarily due to the effect of the new Si II transition probabilities. However, these atomic data are not only very different from previous calculations, but also show large disagreements with measurements, specifically those of Calamai et al. for the intercombination lines. New measurements of transition probabilities for Si II are hence urgently required to confirm (or otherwise) the accuracy of the recently calculated values. If the new calculations are confirmed, then a long-standing discrepancy between theory and observation will have finally been resolved. However, if the older measurements are found to be correct, then the agreement between theory and observation is simply a coincidence and the existing discrepancies remain.

Commentary on Star Chamber Decree 1566

A decree prohibiting the publication of any book considered to be contrary to statute, injunction, ordinance and letters patents, as well as banning the importation of such works. This provided the first occasion on which the proprietary interests of the Stationers' Company and the ideological control of the press become explicitly linked.
The commentary describes the background to the Decree and in particular the concern of Elizabeth's High Commission over the influx of Catholic texts from continental Europe. The commentary argues that the Decree is particularly significant in that it formalised, for the first time, the specific link between the interests of the government in regulating and censuring the press and the economic interests of the Stationers' Company. The formal inclusion of the category of ‘letters patents' within the remit of the Decree ensured that works published under a printing privilege now attracted the formal protection of the Star Chamber.

Commentary on Star Chamber Decree 1586

A decree prohibiting the publication of any book contrary to statute, injunction, ordinance and letters patents, as well as any ordinance set down by the Company of Stationers. The formal protection of the Star Chamber was extended not only to books protected under royal printing privileges (see: uk_1566) but to books printed in contravention of the internal regulations of the Stationers' Company itself, further enhancing the significance of ‘stationers' copyright'.
The commentary describes the background to the decree, in particular the religious controversies of the 1570s and 1580s, as well as the dissatisfaction within the general printing trade during this period at the manner in which a number of the printing privileges granted by Elizabeth resulted in the monopolistic control of commercially lucrative works within the hands of a few stationers only. The commentary also details the efforts of the dominant members of the Stationers' Company to influence the substance of the decree and further augment their control over the internal operation of the book trade.

Commentary on Star Chamber Decree 1637

A decree of the Star Chamber designed to regulate the printing of all literary works, whether ecclesiastical or secular in nature. The decree further entrenched the significance and validity of ‘stationers' copyright' in requiring that no work be printed without first being entered on the Company of Stationers' Register Book. The decree also provided that any materials printed thereafter were to carry both the name of the printer and the author of the work.
The commentary describes how, by comparison with earlier decrees (see: uk_1566; uk_1586), the 1637 Decree provided a more elaborate system for licensing both ecclesiastical and secular works as well as a more comprehensive set of regulations to govern the operation of the printing trade. As a regulatory measure, it is widely regarded as representing the high point of the Company of Stationers' control and authority over the book trade.

The fastest unbound star in our Galaxy ejected by a thermonuclear supernova

Hypervelocity stars (HVSs) travel with velocities so high that they exceed the escape velocity of the Galaxy. Several acceleration mechanisms have been discussed. Only one HVS (US 708, HVS 2) is a compact helium star. Here we present a spectroscopic and kinematic analysis of US 708. Traveling with a velocity of ∼1200 kilometers per second, it is the fastest unbound star in our Galaxy. In reconstructing its trajectory, the Galactic center becomes very unlikely as an origin, which is hardly consistent with the most favored ejection mechanism for the other HVSs. Furthermore, we detected that US 708 is a fast rotator. According to our binary evolution model, it was spun-up by tidal interaction in a close binary and is likely to be the ejected donor remnant of a thermonuclear supernova.

The VLT-FLAMES Tarantula survey: XX. The nature of the X-ray bright emission-line star VFTS 399

Context: The stellar population of the 30 Doradus star-forming region in the Large Magellanic Cloud contains a subset of apparently single, rapidly rotating O-type stars. The physical processes leading to the formation of this cohort are currently uncertain. 

Aims: One member of this group, the late O-type star VFTS 399, is found to be unexpectedly X-ray bright for its bolometric luminosity-in this study we aim to determine its physical nature and the cause of this behaviour. 

Methods: To accomplish this we performed a time-resolved analysis of optical, infrared and X-ray observations. 

Results: We found VFTS 399 to be an aperiodic photometric variable with an apparent near-IR excess. Its optical spectrum demonstrates complex emission profiles in the lower Balmer series and select He i lines-taken together these suggest an OeBe classification. The highly variable X-ray luminosity is too great to be produced by a single star, while the hard, non-thermal nature suggests the presence of an accreting relativistic companion. Finally, the detection of periodic modulation of the X-ray lightcurve is most naturally explained under the assumption that the accretor is a neutron star. 

Conclusions: VFTS 399 appears to be the first high-mass X-ray binary identified within 30 Dor, sharing many observational characteristics with classical Be X-ray binaries. Comparison of the current properties of VFTS 399 to binary-evolution models suggests a progenitor mass 25 M_⊙ for the putative neutron star, which may host a magnetic field comparable in strength to those of magnetars. VFTS 399 is now the second member of the cohort of rapidly rotating "single" O-type stars in 30 Dor to show evidence of binary interaction resulting in spin-up, suggesting that this may be a viable evolutionary pathway for the formation of a subset of this stellar population.

The VLT-FLAMES Tarantula Survey. XV. VFTS 822: A candidate Herbig B[e] star at low metallicity

We report the discovery of the B[e] star VFTS 822 in the 30 Doradus star-forming region of the Large Magellanic Cloud, classified by optical spectroscopy from the VLT-FLAMES Tarantula Survey and complementary infrared photometry. VFTS 822 is a relatively low-luminosity (log L = 4.04 ± 0.25 L_·) B8[e] star. In this Letter, we evaluate the evolutionary status of VFTS 822 and discuss its candidacy as a Herbig B[e] star. If the object is indeed in the pre-main sequence phase, it would present an exciting opportunity to spectroscopically measure mass accretion rates at low metallicity, to probe the effect of metallicity on accretion rates. 

The Last Minutes of Oxygen Shell Burning in a Massive Star

We present the first 3D simulation of the last minutes of oxygen shell burning in an 18 solar mass supernova progenitor up to the onset of core collapse. A moving inner boundary is used to accurately model the contraction of the silicon and iron core according to a 1D stellar evolution model with a self-consistent treatment of core deleptonization and nuclear quasi-equilibrium. The simulation covers the full solid angle to allow the emergence of large-scale convective modes. Due to core contraction and the concomitant acceleration of nuclear burning, the convective Mach number increases to ~0.1 at collapse, and an l=2 mode emerges shortly before the end of the simulation. Aside from a growth of the oxygen shell from 0.51 to 0.56 solar masses due to entrainment from the carbon shell, the convective flow is reasonably well described by mixing length theory, and the dominant scales are compatible with estimates from linear stability analysis. We deduce that artificial changes in the physics, such as accelerated core contraction, can have precarious consequences for the state of convection at collapse. We argue that scaling laws for the convective velocities and eddy sizes furnish good estimates for the state of shell convection at collapse and develop a simple analytic theory for the impact of convective seed perturbations on shock revival in the ensuing supernova. We predict a reduction of the critical luminosity for explosion by 12--24% due to seed asphericities for our 3D progenitor model relative to the case without large seed perturbations.

The Physical and Chemical Structure of Hot Molecular Cores

We have made self-consistent models of the density and temperature profiles of the gas and dust surrounding embedded luminous objects using a detailed radiative transfer model together with observations of the spectral energy distribution of hot molecular cores. Using these profiles we have investigated the hot core chemistry which results when grain mantles are evaporated, taking into account the different binding energies of the mantle molecules, as well a model in which we assume that all molecules are embedded in water ice and have a common binding energy. We find that most of the resulting column densities are consistent with those observed toward the hot core G34.3+0.15 at a time around 10^4 years after central luminous star formation. We have also investigated the dependence of the chemical structure on the density profile which suggests an observational possibility of constraining density profiles from determination of the source sizes of line emission from desorbed molecules.

Molecular Hydrogen Emission from Protoplanetary Disks

We have modeled self-consistently the density and temperature profiles of gas and dust in protoplanetary disks, taking into account irradiation from a central star. Making use of this physical structure, we have calculated the level populations of molecular hydrogen and the line emission from the disks. As a result, we can reproduce the observed strong line spectra of molecular hydrogen from protoplanetary disks, both in the ultraviolet (UV) and the near-infrared, but only if the central star has a strong UV excess radiation.

Enhanced Deuterium Fractionation in Dense Interstellar Cores Resulting from Multiply Deuterated H3+

In this Letter, we present the first results from updated models of interstellar deuterium chemistry that now include all possible deuterated isotopomers of H3+. We find that in regions of high density and heavy depletion, such as prestellar cores, the inclusion of HD2+ and D3+ enhances the fractionation of ionic and neutral species significantly. Our models are the first to predict the very high atomic D/H ratios (>=0.3) necessary for grain-surface chemistry models to reproduce the high formaldehyde and methanol fractionation seen in star-forming regions.

Professional Educational Psychology and Community Relations Education in Northern Ireland.

This article provides an account of practice-based research of, at least, one-star quality in terms of its contribution to both theory and practice. Aimed at practitioner (as opposed to academic) psychologists, the article addresses a dimension of the practitioner role that has remained silent in the literature. The article makes creative and original connections between school effectiveness, school improvement and education in a divided society. Post 11th September, the article was described as being highly original, significant and relevant to all practising educational psychologists. Concrete evidence for this is gained from, eg: hits on the online electronic version (2002-2003 Annual Report of the Association of Educational Psychologists), citations in reviews of research, and author invitations to present his work at UK and international practitioner psychology conferences. The article is published in the premier journal reporting on quality applied educational research and practice within the United Kingdom and beyond.

Observations of the interstellar medium in the Magellanic Bridge.

We present ultraviolet and optical spectra of DI 1388, a young star in the Magellanic Bridge, a region of gas between the Small and Large Magellanic Clouds. The data have signal-to-noise ratios of 20-45 and a spectral resolution of 6.5 km s-1. Interstellar absorption by the Magellanic Bridge at vLSR~200 km s-1 is visible in the lines of C I, C II, C II*, C IV, N I, O I, Al II, Si II, Si III, Si IV, S II, Ca II, Fe II, and Ni II. The relative gas-phase abundances of C II, N I, O I, Al II, Si II, Fe II, and Ni II with respect to S II are similar to those found in Galactic halo clouds, despite a significantly lower metallicity in the Magellanic Bridge. The higher ionization species in the cloud have a column density ratio N(C+3)/N(Si+3)~1.9, similar to that inferred for collisionally ionized Galactic cloud interfaces at temperatures ~105 K. We identify substructure in the stronger interstellar lines, with a broad component (FWHM~20 km s-1) at ~179 km s-1 and a sharp component (FWHM~11 km s-1) at 198 km s-1. The abundance analysis for these clouds indicates that the feature at 198 km s-1 consists of a low electron density, mainly neutral gas that may be associated with an interface responsible for the highly ionized gas. The 179 km s-1 cloud consists of warmer, lower density gas that is partially ionized.

Macroturbulent and rotational broadening in the spectra of B-type supergiants.

The absorption-line spectra of early B-type supergiants show significant broadening that implies that an additional broadening mechanism (characterized here as `macroturbulence') is present in addition to rotational broadening. Using high-resolution spectra with signal-to-noise ratios of typically 500, we have attempted to quantify the relative contributions of rotation and macroturbulence, but even with data of this quality significant problems were encountered. However, for all our targets, a model where macroturbulence dominates and rotation is negligible is acceptable; the reverse scenario leads to poor agreement between theory and observation. Additionally, there is marginal evidence for the degree of broadening increasing with line strength, possibly a result of the stronger lines being formed higher in the atmosphere. Acceptable values of the projected rotational velocity are normally less than or equal to 50 km s-1, which may also be a typical upper limit for the rotational velocity. Our best estimates for the projected rotational velocity are typically 10-20 km s-1 and hence compatible with this limit. These values are compared with those predicted by single star evolutionary models, which are initially rapidly rotating. It is concluded that either these models underestimate the rate of rotational breaking or some of the targets may be evolving through a blue loop or are binaries.