Discovery of a Two-Armed Spiral Structure in the Gapped Disk in HD 100453

We present VLT/SPHERE adaptive optics imaging in Y$-$, J$-$, H$-$, and K-bands of the HD 100453 system and the discovery of a two-armed spiral structure in a disk extending to 0.37" ($\sim$42 AU) from the star, with highly symmetric arms to the Northeast and Southwest. Inside of the spiral arms, we resolve a ring of emission from 0.18"-0.25" ($\sim$21-29 AU). By assuming that the ring is intrinsically circular we estimate an inclination of $\sim$34$^{o}$ from face-on. We detect dark crescents on opposite sides (NW and SE) which begin at 0.18" and continue to radii smaller than our inner working angle of 0.15", which we interpret as the signature of a gap at $\lesssim$21 AU that has likely been cleared by forming planets. We also detect the $\sim$120 AU companion HD 100453 B, and by comparing our data to 2003 HST/ACS and VLT/NACO images we estimate an orbital period of $\sim$850 yr. We discuss what implications the discovery of the spiral arms and finer structures of the disk may have on our understanding of the possible planetary system in HD 100453, and how the morphology of this disk compares to other related objects.Comment: 12 pages, 5 figures, accepted for publication in ApJ

Gearing up the SPHERE

Direct imaging and spectral characterisation of exoplanets is one of the most exciting, but also one of the most challenging areas, in modern astronomy. The challenge is to overcome the very large contrast between the host star and its planet seen at very small angular separations. This article reports on the progress made in the construction of the second generation VLT instrument SPHERE, the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument. SPHERE is expected to be commissioned on the VLT in 2013

PSF reconstruction for NAOS-CONICA

Adaptive optics (AO) allows one to derive the point spread function (PSF) simultaneously to the science image, which is a major advantage in post-processing tasks such as astrometry/photometry or deconvolution. Based on the algorithm of \citet{veran97}, PSF reconstruction has been developed for four different AO systems so far: PUEO, ALFA, Lick-AO and Altair. A similar effort is undertaken for NAOS/VLT in a collaboration between the group PHASE (Onera and Observatoire de Paris/LESIA) and ESO. In this paper, we first introduce two new algorithms that prevent the use of the so-called "$U\_{ij}$ functions" to: (1) avoid the storage of a large amount of data (for both new algorithms), (2) shorten the PSF reconstruction computation time (for one of the two) and (3) provide an estimation of the PSF variability (for the other one). We then identify and explain issues in the exploitation of real-time Shack-Hartmann (SH) data for PSF reconstruction, emphasising the large impact of thresholding in the accuracy of the phase residual estimation. Finally, we present the data provided by the NAOS real-time computer (RTC) to reconstruct PSF ({\em (1)} the data presently available, {\em (2)} two NAOS software modifications that would provide new data to increase the accuracy of the PSF reconstruction and {\em (3)} the tests of these modifications) and the PSF reconstruction algorithms we are developing for NAOS on that basis.Comment: 12 pages & 13 figures. To be published in the proceedings of the SPIE conference Advances in Adaptive Optics - Astronomical Telescopes & Instrumentation, 24-31 May 2006, Orland

Managing rapport in talk: using rapport sensitive incidents to explore the motivational concerns underlying the management of relations

This paper focuses on the motivational concerns that underlie the management of relations. In linguistics, the management of relations has been discussed extensively within politeness theory, and so the paper starts by identifying four key issues of controversy in politeness theory: (a) should ‘polite’ language use be explained in terms of face (e.g. Brown, Penelope, Levinson, Stephen C., 1987. Politeness. Some Universals in Language Usage, CUP, Cambridge. [Originally published as Universals in Language Usage: Politeness Phenomenon. In: Goody, Esther, (Ed.), Questions and Politeness: Strategies in Social Interaction. CUP, New York, 1978), conversational maxims (e.g. Leech, Geoffrey N., 1983. Principles of Pragmatics. Longman, London), and/or conversational rights (e.g. Fraser, Bruce, 1990. Perspectives on politeness. Journal of Pragmatics 14 (2), 219–236); (b) why are speech acts such as orders interpersonally sensitive — is it because they are a threat to our autonomy (Brown and Levinson, 1987 [1978]), or because of cost–benefit concerns (Leech, 1983); (c) is Brown and Levinson's concept of negative face too individually focused, and should a social identity component be included (Matsumoto, Yoshiko, 1988. Reexamination of the universality of face: politeness phenomena in Japanese. Journal of Pragmatics 12, 403–426); and (d) is face just a personal/individual concern or can it be a group concern (Gao, Ge, 1996. Self and other: a Chinese perspective on interpersonal relationships. In: Gudykunst, W.B., Ting-Toomey, S., Nishida, T. (Eds.), Communication in Personal Relationships Across Cultures, Sage, London. pp. 81–101.)? The paper then uses reports of authentic rapport sensitive incidents to throw light on these controversial issues and to find out the relational management concerns that people perceive in their everyday lives. It maintains that such data is important to politeness theory, because linguistic politeness needs to be studied within the situated social psychological context in which it occurs. The paper ends by presenting and arguing for a conceptual framework that draws a fundamental distinction between face and sociality rights, and that incorporates an independent/interdependent perspective, thus providing a more comprehensive framework for analysing the management of relations than is currently available

A young protoplanet candidate embedded in the circumstellar disk of HD100546

We present high-contrast observations of the circumstellar environment of the Herbig Ae/Be star HD100546. The final 3.8 micron image reveals an emission source at a projected separation of 0.48"+-0.04" (corresponding to ~47+-4 AU at a position angle of 8.9+-0.9 degree. The emission appears slightly extended with a point source component with an apparent magnitude of 13.2+-0.4 mag. The position of the source coincides with a local deficit in polarization fraction in near-infrared polarimetric imaging data, which probes the surface of the well-studied circumstellar disk of HD100546. This suggests a possible physical link between the emission source and the disk. Assuming a disk inclination of ~47 degree the de-projected separation of the object is ~68 AU. Assessing the likelihood of various scenarios we favor an interpretation of the available high-contrast data with a planet in the process of forming. Follow-up observations in the coming years can easily distinguish between the different possible scenarios empirically. If confirmed, HD100546 "b" would be a unique laboratory to study the formation process of a new planetary system, with one giant planet currently forming in the disk and a second planet possibly orbiting in the disk gap at smaller separations.Comment: Accepted by ApJ Letters (published online February 28, 2013

An apodizing phase plate coronagraph for VLT/NACO

We describe a coronagraphic optic for use with CONICA at the VLT that provides suppression of diffraction from 1.8 to 7 lambda/D at 4.05 microns, an optimal wavelength for direct imaging of cool extrasolar planets. The optic is designed to provide 10 magnitudes of contrast at 0.2 arcseconds, over a D-shaped region in the image plane, without the need for any focal plane occulting mask.Comment: 9 pages, 5 figures, to appear in Proc. SPIE Vol. 773

The Orbit of the Companion to HD 100453A: Binary-Driven Spiral Arms in a Protoplanetary Disk

HD 100453AB is a 10+/-2 Myr old binary whose protoplanetary disk was recently revealed to host a global two-armed spiral structure. Given the relatively small projected separation of the binary (1.05", or ~108 au), gravitational perturbations by the binary seemed to be a likely driving force behind the formation of the spiral arms. However, the orbit of these stars remained poorly understood, which prevented a proper treatment of the dynamical influence of the companion on the disk. We observed HD 100453AB between 2015-2017 utilizing extreme adaptive optics systems on the Very Large Telescope and Magellan Clay Telescope. We combined the astrometry from these observations with published data to constrain the parameters of the binary's orbit to a=1.06"+/-0.09", e=0.17+/-0.07, and i=32.5+/- 6.5 degrees. We utilized publicly available ALMA CO data to constrain the inclination of the disk to i~28 degrees, which is relatively co-planar with the orbit of the companion and consistent with previous estimates from scattered light images. Finally, we input these constraints into hydrodynamical and radiative transfer simulations to model the structural evolution of the disk. We find that the spiral structure and truncation of the circumprimary disk in HD 100453 are consistent with a companion-dirven origin. Furthermore, we find that the primary star's rotation, its outer disk, and the companion exhibit roughly the same direction of angular momentum, and thus the system likely formed from the same parent body of material.Comment: 28 pages, 11 figures, Accepted to Ap

Image quality and high contrast improvements on VLT/NACO

NACO is the famous and versatile diffraction limited NIR imager and spectrograph with which ESO celebrated 10 years of Adaptive Optics at the VLT. Since two years a substantial effort has been put in to understanding and fixing issues that directly affect the image quality and the high contrast performances of the instrument. Experiments to compensate the non-common-path aberrations and recover the highest possible Strehl ratios have been carried out successfully and a plan is hereafter described to perform such measurements regularly. The drift associated to pupil tracking since 2007 was fixed in October 2011. NACO is therefore even better suited for high contrast imaging and can be used with coronagraphic masks in the image plane. Some contrast measurements are shown and discussed. The work accomplished on NACO will serve as reference for the next generation instruments on the VLT, especially those working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, possibly ERIS).Comment: 14 pages, 5 figures, SPIE 2012 Astronomical Instrumentation Proceedin