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TOPIC: Beta Pictoris
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Title: First Detection of Hydrogen in the Beta Pictoris Gas Disk
Author: P. A. Wilson, A. Lecavelier des Etangs, A. Vidal-Madjar, V. Bourrier, G. Hébrard, F. Kiefer, H. Beust, R. Ferlet, A.-M. Lagrange

The young and nearby star beta Pictoris (beta Pic) is surrounded by a debris disk composed of dust and gas known to host a myriad evaporating exocomets, planetesimals and at least one planet. At an edge-on inclination, as seen from Earth, this system is ideal for debris disk studies providing an excellent opportunity to use absorption spectroscopy to study the planet forming environment. Using the Cosmic Origins Spectrograph (COS) instrument on the Hubble Space Telescope (HST) we observe the most abundant element in the disk, hydrogen, through the HI Lyman alpha (Ly-alpha) line. We present a new technique to decrease the contamination of the Ly-alpha line by geocoronal airglow in COS spectra. This Airglow Virtual Motion (AVM) technique allows us to shift the Ly-alpha line of the astrophysical target away from the contaminating airglow emission revealing more of the astrophysical line profile. The column density of hydrogen in the beta Pic stable gas disk at the stellar radial velocity is measured to be log(N_H/1cm^2) << 18.5. The Ly-alpha emission line profile is found to be asymmetric and we propose that this is caused by HI falling in towards the star with a bulk radial velocity of 41±6 km/s relative to beta Pic and a column density of log(N_H 1cm^2)=18.6±0.1. The high column density of hydrogen relative to the hydrogen content of CI chondrite meteorites indicates that the bulk of the hydrogen gas does not come from the dust in the disk. This column density reveals a hydrogen abundance much lower than solar, which excludes the possibility that the detected hydrogen could be a remnant of the protoplanetary disk or gas expelled by the star. We hypothesise that the hydrogen gas observed falling towards the star arises from the dissociation of water originating from evaporating exocomets.

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Title: Beta Pictoris' inner disk in polarized light and new orbital parameters for Beta Pictoris b
Author: Maxwell A. Millar-Blanchaer, James R. Graham, Laurent Pueyo, Paul Kalas, Rebekah I. Dawson, Jason Wang, Marshall Perrin, Dae-Sik Moon, Bruce Macintosh, S. Mark Ammons, Travis Barman, Andrew Cardwell, Christine H. Chen, Eugene Chiang, Jeffrey Chilcote, Tara Cotten, Robert J. De Rosa, Zachary H. Draper, Jennifer Dunn, Gaspard Duchêne, Thomas M. Esposito, Michael P. Fitzgerald, Katherine B. Follette, Stephen J. Goodsell, Alexandra Z. Greenbaum, Markus Hartung, Pascale Hibon, Sasha Hinkley, Patrick Ingraham, Rebecca Jensen-Clem, Quinn Konopacky, James E. Larkin, Douglas Long, Jérôme Maire, Franck Marchis, Mark S. Marley, Christian Marois, Katie M. Morzinski, Eric L. Nielsen, David W. Palmer, Rebecca Oppenheimer, Lisa Poyneer, Abhijith Rajan, Fredrik T. Rantakyrö, Jean-Baptiste Ruffio, et al. (12 additional authors not shown)

We present H-band observations of Pic with the Gemini Planet Imager's (GPI's) polarimetry mode that reveal the debris disk between ~0.3" (~6 AU) and ~1.7" (~33 AU), while simultaneously detecting B Pic b. The polarised disk image was fit with a dust density model combined with a Henyey-Greenstein scattering phase function. The best fit model indicates a disk inclined to the line of sight (phi=85.27deg^{+0.26}_{-0.19}) with a position angle theta_{PA}=30.35{\deg}^{+0.29}_{-0.28} (slightly offset from the main outer disk, theta_{PA} approx 29deg), that extends from an inner disk radius of 23.6^{+0.9}_{-0.6} AU to well outside GPI's field of view. In addition, we present an updated orbit for B Pic b based on new astrometric measurements taken in GPI's spectroscopic mode spanning 14 months. The planet has a semi-major axis of a=9.2^{+1.5}_{-0.4} AU, with an eccentricity e \leq 0.26. The position angle of the ascending node is Omega=31.75deg±0.15, offset from both the outer main disk and the inner disk seen in the GPI image. The orbital fit constrains the stellar mass of B Pic to 1.60±0.05 solar masses. Dynamical sculpting by B Pic b cannot easily account for the following three aspects of the inferred disk properties: 1) the modelled inner radius of the disk is farther out than expected if caused by Pic b; 2) the mutual inclination of the inner disk and B Pic b is 4deg, when it is expected to be closer to zero; and 3) the aspect ratio of the disk (h_0 = 0.137^{+0.005}_{-0.006}) is larger than expected from interactions with B Pic b or self-stirring by the disk's parent bodies.

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Discovery of cometary crystals in a younger brother of our solar system

A team led by astronomers of the KU Leuven found that the dusty disk around the young star Beta Pictoris contains olivine crystals strikingly similar to those found in comets of our Solar System. The discovery is an important piece in the puzzle to understand how our Solar System was formed. The results are published on October 4th 2012 in the journal Nature.
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Hubble Gets Best View of a Circumstellar Debris Disk Distorted by a Planet

Over a decade before planets were found orbiting normal stars, the astronomy world was intrigued by the discovery of a vast, edge-on, pancake-flat disk of dust and gas encircling the newborn star Beta Pictoris. It appeared to validate the hypothesis by the German philosopher Immanuel Kant, 230 years ago, that our solar system was born when planets condensed from nebular material in the plane of such a disk. (This model was independently proposed by French scholar Pierre-Simon Laplace in 1796.) Kant regarded the coplanar obits of the planets a fossil skeleton of the long-ago disintegrated disk. Though nearly two dozen circumstellar debris disks have been viewed by the Hubble Space Telescope to date, Beta Pictoris is the first and best example of what a forming young planetary system looks like.
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Two Families of Comets Found Around Nearby Star

The HARPS instrument at ESOs La Silla Observatory in Chile has been used to make the most complete census of comets around another star ever created. A French team of astronomers has studied nearly 500 individual comets orbiting the star Beta Pictoris and has discovered that they belong to two distinct families of exocomets: old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects. The new results will appear in the journal Nature on 23 October 2014.
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Beta Pictoris b
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Title: The First H-band Spectrum of the Massive Gas Giant Planet beta Pictoris b with the Gemini Planet Imager
Author: Jeffrey Chilcote, Travis Barman, Michael P. Fitzgerald, James R. Graham, James E. Larkin, Bruce Macintosh, Brian Bauman, Adam S. Burrows, Andrew Cardwell, Robert J. De Rosa, Daren Dillon, Rene Doyon, Jennifer Dunn, Darren Erikson, Donald Gavel, Stephen J. Goodsell, Markus Hartung, Pascale Hibon, Patrick Ingraham, Paul Kalas, Quinn Konopacky, Jérôme Maire, Franck Marchis, Mark S. Marley, Christian Marois, Max Millar-Blanchaer, Katie Morzinski, Andrew Norton, B. R. Oppenheimer, David Palmer, Jennifer Patience, Marshall D. Perrin, Lisa Poyneer, Laurent Pueyo, Fredrik Rantakyrö, Naru Sadakuni, Leslie Saddlemyer, Dmitry Savransky, Andrew Serio, Anand Sivaramakrishnan, Inseok Song, Remi Soummer, Sandrine Thomas, J. Kent Wallace, Sloane J. Wiktorowicz, Schuyler Wolff

Using the recently installed Gemini Planet Imager (GPI), we have taken the first H-band spectrum of the planetary companion to the nearby young star beta Pictoris. GPI is designed to image and provide low-resolution spectra of Jupiter sized, self-luminous planetary companions around young nearby stars. These observations were taken covering the H-band (1.65 microns). The spectrum has a resolving power of ~ 45 and demonstrates the distinctive triangular shape of a cool substellar object with low surface gravity. Using atmospheric models, we find an effective temperature of 1650±50 K and a surface gravity of log(g)=4.0±0.25 (cgs units). These values agree well with predictions from planetary evolution models for a gas giant with mass between 10 and 12 MJup and age between 10 and 20 Myrs.

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beta Pictoris debris disc
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Title: Very deep images of the innermost regions of the beta Pictoris debris disc at Lp
Author: J. Milli, A.-M. Lagrange, D. Mawet, O. Absil, J.-C. Augereau, D. Mouillet, A. Boccaletti, J. H. Girard, G. Chauvin

Very few debris discs have been imaged in scattered light at wavelengths beyond 3 microns because the thermal emission from both the sky and the telescope is generally too strong with respect to the faint emission of a debris disc. We present here the first analysis of a high angular resolution image of the disc of beta Pictoris at 3.8 microns. Our primary objective is to probe the innermost parts of the beta Pictoris debris disc and describe its morphology. We performed extensive forward modelling to correct for the biases induced by angular differential imaging on extended objects and derive the physical parameters of the disc. This work relies on a new analysis of seven archival datasets of beta Pictoris observed with VLT/NaCo in the Lp band, associated with disc forward modelling to correct for the biases induced by that technique. The disc is detected above a 5 sigma level between 0.4" and 3.8". The two extensions have a similar brightness within error bars. We confirm an asymmetry previously observed at larger distances from the star and at shorter wavelengths: the isophotes are more widely spaced on the north-west side (above the disc apparent midplane) than on the south-east side. This is interpreted as a small inclination of the disc combined with anisotropic scattering. Our best-fit model has an inclination of 86 degrees with an anisotropic Henyey- Greenstein coefficient of 0.36. This interpretation is supported by a new asymmetry detected in the disc: the disc is significantly bowed towards the north-west within 3" (above the apparent midplane). We also detect a possible new asymmetry within 1", but at this stage we cannot discern between a real feature and an underlying speckle.

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Blobrana


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Zooming in on Beta Pictoris b

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Beta Pictoris b
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Length of Exoplanet Day Measured for First Time

Observations from ESO's Very Large Telescope (VLT) have, for the first time, determined the rotation rate of an exoplanet. Beta Pictoris b has been found to have a day that lasts only eight hours. This is much quicker than any planet in the Solar System - its equator is moving at almost 100 000 kilometres per hour. This new result extends the relation between mass and rotation seen in the Solar System to exoplanets. Similar techniques will allow astronomers to map exoplanets in detail in the future with the European Extremely Large Telescope (E-ELT).
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Beta Pictoris
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Title: Molecular Gas Clumps from the Destruction of Icy Bodies in the Beta Pictoris Debris Disk
Author: W.R.F. Dent, M.C. Wyatt, A. Roberge, J.-C. Augereau, S. Casassus, S. Corder, J.S. Greaves, I. de Gregorio-Monsalvo, A. Hales, A.P. Jackson, A. Meredith Hughes, A.-M. Lagrange, B. Matthews, D. Wilner

Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets. But is gas also released in such events? Observations at submm wavelengths of the archetypal debris disk around Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85AU from the star, in a plane closely aligned with the orbit of the inner planet, Beta Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

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