14 research outputs found
Resolved near-UV hydrogen emission lines at 40-Myr super-Jovian protoplanet Delorme 1 (AB)b: Indications of magnetospheric accretion
We have followed up on our observations of the ~ 40-Myr, and still accreting,
PMC Delorme 1 (AB)b. We used high-resolution spectroscopy to characterise the
accretion process further by accessing the wealth of emission lines in the
near-UV. With VLT/UVES, we obtained R ~ 50000 spectroscopy at 330--452 nm.
After separating the emission of the companion from that of the M5 low-mass
binary, we performed a detailed emission-line analysis, which included
planetary accretion shock modelling. We reaffirm ongoing accretion in Delorme 1
(AB)b and report the first detections in a (super-Jovian) protoplanet of
resolved hydrogen line emission in the near-UV (H-gamma, H-delta, H-epsilon, H8
and H9). We tentatively detect H11, H12, He I and Ca II H/K. The analysis
strongly favours a planetary accretion shock with a line-luminosity-based
accretion rate dMp/dt = 2e-8 MJ/yr. The lines are asymmetric and well described
by sums of narrow and broad components with different velocity shifts. Overall
line shapes are best explained by a pre-shock velocity v0 = 170+-30 km/s,
implying a planetary mass Mp = 13+-5 MJ, and number densities n0 ~ 1e13/cc or
n0 ~ 1e11/cc. The higher density implies a small line-emitting area of ~ 1%
relative to the planetary surface. This favours magnetospheric accretion, a
case potentially strengthened by the presence of blueshifted emission in the
asymmetrical profiles.High-resolution spectroscopy offers the opportunity to
resolve line profiles, crucial for studying the accretion process in depth. The
super-Jovian protoplanet Delorme 1 (AB)b is still accreting at ~ 40 Myr. Thus,
Delorme 1 belongs to the growing family of Peter Pan disc systems with
protoplanetary and/or circumplanetary disc(s) far beyond the typically assumed
disc lifetimes. Further observations of this benchmark companion, and its
presumed disc(s), will help answer key questions about the accretion geometry
in PMCs.Comment: Published in A&A 669, L12, 11 pages, abbreviated abstrac
Imaging of exocomets with infrared interferometry
Active comets have been detected in several exoplanetary systems, although so
far only indirectly, when the dust or gas in the extended coma has transited in
front of the stellar disk. The large optical surface and relatively high
temperature of an active cometary coma also makes it suitable to study with
direct imaging, but the angular separation is generally too small to be
reachable with present-day facilities. However, future imaging facilities with
the ability to detect terrestrial planets in the habitable zones of nearby
systems will also be sensitive to exocomets in such systems. Here we examine
several aspects of exocomet imaging, particularly in the context of the Large
Interferometer for Exoplanets (LIFE), which is a proposed space mission for
infrared imaging and spectroscopy through nulling interferometry. We study what
capabilities LIFE would have for acquiring imaging and spectroscopy of
exocomets, based on simulations of the LIFE performance as well as statistical
properties of exocomets that have recently been deduced from transit surveys.
We find that for systems with extreme cometary activities such as beta
Pictoris, sufficiently bright comets may be so abundant that they overcrowd the
LIFE inner field of view. More nearby and moderately active systems such as
epsilon Eridani or Fomalhaut may turn out to be optimal targets. If the
exocomets have strong silicate emission features, such as in comet Hale-Bopp,
it may become possible to study the mineralogy of individual exocometary
bodies. We also discuss the possibility of exocomets as false positives for
planets, with recent deep imaging of alpha Centauri as one hypothetical
example. Such contaminants could be common, primarily among young debris disk
stars, but should be rare among the main sequence population. We discuss
strategies to mitigate the risk of any such false positives.Comment: 17 pages, 11 figures, accepted for publication in A&
BEAST detection of a brown dwarf and a low-mass stellar companion around the young bright B star HIP 81208
Recent observations from B-star Exoplanet Abundance Study (BEAST) have
illustrated the existence of sub-stellar companions around very massive stars.
In this paper, we present the detection of two lower mass companions to a
relatively nearby ( pc), young ( Myr),
bright (V= mag), B9V star HIP 81208
residing in the Sco-Cen association, using the Spectro-Polarimetric
High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large
Telescope (VLT) in Chile. Analysis of the photometry obtained gives mass
estimates of for the inner companion and
for the outer companion, indicating the
former to be most likely a brown dwarf and the latter to be a low-mass star.
The system is compact but unusual, as the orbital planes of the two companions
are likely close to orthogonal. The preliminary orbital solutions we derived
for the system indicate that the star and the two companions are likely in a
Kozai resonance, rendering the system dynamically very interesting for future
studies.Comment: 18 pages, 14 figures, 5 tables Accepted for publication in the 10.
Planets and planetary systems section of A&
2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS guideline for the diagnosis and management of patients with stable ischemic heart disease
The recommendations listed in this document are, whenever possible, evidence based. An extensive evidence review was conducted as the document was compiled through December 2008. Repeated literature searches were performed by the guideline development staff and writing committee members as new issues were considered. New clinical trials published in peer-reviewed journals and articles through December 2011 were also reviewed and incorporated when relevant. Furthermore, because of the extended development time period for this guideline, peer review comments indicated that the sections focused on imaging technologies required additional updating, which occurred during 2011. Therefore, the evidence review for the imaging sections includes published literature through December 2011
Unveiling the Accretion Process at Planetary Masses
Giant planets have had a long history of radically overturning our expectations of how they form and where they are likely to be found around other stars. In 1995, the first exoplanet detected around a Sun-like star was not found further out from the star, as expected from the locations of Jupiter and Saturn and then current formation theories, but rather on a 4-day orbit with a surface temperature just above the melting point of silver and a radius nearly twice that of Jupiter. Since then we have detected thousands of exoplanets, which have shown remarkable diversity, and imaged the discs around young stars where baby planets are being born. Although there are many common characteristics of these exoplanets and discs, some stand out as outliers. There are systems that are thought âtoo oldâ to form planets, or planetary-mass companions that are âtoo bigâ in relation to their host stars or should not have had the time to grow that massive to begin with. These are some of the (many) outstanding questions on the frontier of research into planet formation, and in just the past few years we have finally been able to directly observe a few planets that are in the process of forming. In an almost parallel development to the rapid expansion of research into exoplanets, we have also come to realise that brown dwarfs can be excellent analogues to giant planets and contribute significantly to our understanding of both the atmospheres and the formation process of giant planets. This thesis explores several aspects of the dynamics of substellar atmospheres and the accretion process at planetary masses. It discusses the observing methods, which provide the foundations of the photometric and spectroscopic observations that produced the data for the included papers. This is followed by a chapter on star and planet formation and one discussing the variability of substellar atmospheres. The final chapter delves more directly into the observational features of accretion and the tracers and diagnostics which enable us to start qualitatively characterise the accretion process at planetary masses. The first paper presents a NOT/NOTCam photometric survey of ten brown dwarfs, where the goal was to identify new high-amplitude variables that could be suitable for deeper studies. A large fraction was found to be variable, significantly adding to the number of known variable brown dwarfs. In the second paper, integral field spectroscopy obtained with VLT/MUSE of the planetary-mass companion Delorme 1 (AB)b and its host binary star is presented. Very strong hydrogen line emission was detected from the companion, indicative of active accretion in this 40-myr-old system. In the third paper, Delorme 1 (AB)b was further studied by VLT/UVES and R = 50000 spectroscopy. As a result, near-UV hydrogen emission lines were resolved in a planetary-mass companion for the first time. The analysis of these lines strengthened the case for active accretion in the companion
BEAST detection of a brown dwarf and a low-mass stellar companion around the young bright B star HIP 81208
Recent observations by the B-star Exoplanet Abundance Study (BEAST) illustrate the existence of substellar companions around very massive stars. Here, we present the detection of two lower mass companions to a relatively nearby (148.7ââ.ââșÂč.â” pc), young (17âââșÂł Myr), bright (V = 6.632 ± 0.006 mag), 2.58 ± 0.06 MÊB9V star HIP 81208 residing in the Sco-Cen association using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large Telescope (VLT) in Chile. Our analysis of the photometry obtained gives mass estimates of 67âââșⶠMJ for the inner companion and 0.135ââ.ââââșâ°.â°Âčâ° MÊ for the outer companion, indicating that the former is most likely a brown dwarf and the latter a low-mass star. The system is compact but unusual, as the orbital planes of the two companions are likely close to orthogonal. The preliminary orbital solutions we derive for the system indicate that the star and the two companions are likely in a Kozai resonance, rendering the system dynamically very interesting for future studies.ISSN:0004-6361ISSN:1432-074
Forbidden emission lines in protostellar outflows and jets with MUSE
Context. Forbidden emission lines in protoplanetary disks are a key diagnostic in studies of the evolution of the disk and the host star. They signal potential disk accretion or wind, outflow, or jet ejection processes of the material that affects the angular momentum transport of the disk as a result.
Aims. We report spatially resolved emission lines, namely, [OâŻ
A wide-orbit giant planet in the high-mass b Centauri binary system
Planet formation occurs around a wide range of stellar masses and stellar system architectures^1. An improved understanding of the formation process can be achieved by studying it across the full parameter space, particularly towards the extremes. Earlier studies of planets in close-in orbits around high-mass stars have revealed an increase in giant planet frequency with increasing stellar mass^2 until a turnover point at 1.9 solar masses (M_\ensuremathĂždot), above which the frequency rapidly decreases^3. This could potentially imply that planet formation is impeded around more massive stars, and that giant planets around stars exceeding 3 M_\ensuremathĂždot may be rare or non-existent. However, the methods used to detect planets in small orbits are insensitive to planets in wide orbits. Here we demonstrate the existence of a planet at 560 times the Sun-Earth distance from the 6- to 10-M_\ensuremathĂždot binary b Centauri through direct imaging. The planet-to-star mass ratio of 0.10-0.17% is similar to the Jupiter-Sun ratio, but the separation of the detected planet is about 100 times wider than that of Jupiter. Our results show that planets can reside in much more massive stellar systems than what would be expected from extrapolation of previous results. The planet is unlikely to have formed in situ through the conventional core accretion mechanism^4, but might have formed elsewhere and arrived to its present location through dynamical interactions, or might have formed via gravitational instability
A wide-orbit giant planet in the high-mass b Centauri binary system
Planet formation occurs around a wide range of stellar masses and stellar system architectures1. An improved understanding of the formation process can be achieved by studying it across the full parameter space, particularly towards the extremes. Earlier studies of planets in close-in orbits around high-mass stars have revealed an increase in giant planet frequency with increasing stellar mass2 until a turnover point at 1.9âsolar masses (Mâ), above which the frequency rapidly decreases3. This could potentially imply that planet formation is impeded around more massive stars, and that giant planets around stars exceeding 3âMâ may be rare or non-existent. However, the methods used to detect planets in small orbits are insensitive to planets in wide orbits. Here we demonstrate the existence of a planet at 560 times the SunâEarth distance from the 6- to 10-Mâ binary bâCentauri through direct imaging. The planet-to-star mass ratio of 0.10â0.17% is similar to the JupiterâSun ratio, but the separation of the detected planet is about 100 times wider than that of Jupiter. Our results show that planets can reside in much more massive stellar systems than what would be expected from extrapolation of previous results. The planet is unlikely to have formed in situ through the conventional core accretion mechanism4, but might have formed elsewhere and arrived to its present location through dynamical interactions, or might have formed via gravitational instability
A scaled-up planetary system around a supernova progenitor
Context. Virtually all known exoplanets reside around stars with M < 2.3 M either due to the rapid evaporation of the protostellar disks or to selection effects impeding detections around more massive stellar hosts.
Aims. To clarify if this dearth of planets is real or a selection effect, we launched the planet-hunting B-star Exoplanet Abundance STudy (BEAST) survey targeting B stars (M > 2.4 M) in the young (5â20 Myr) Scorpius-Centaurus association by means of the high-contrast spectro-imager SPHERE at the Very Large Telescope.
Methods. In this paper we present the analysis of high-contrast images of the massive (M ~ 9 M) star Ό Sco obtained within BEAST. We carefully examined the properties of this star, combining data from Gaia and from the literature, and used state-of-the-art algorithms for the reduction and analysis of our observations.
Results. Based on kinematic information, we found that Ό Sco is a member of a small group which we label Eastern Lower Scorpius within the Scorpius-Centaurus association. We were thus able to constrain its distance, refining in turn the precision on stellar parameters. Around this star we identify a robustly detected substellar companion (14.4 ± 0.8 M)at a projected separation of 290 ± 10 au, and a probable second similar object (18.5 ± 1.5 M) at 21 ± 1 au. The planet-to-star mass ratios of these objects are similar to that of Jupiter to the Sun, and the flux they receive from the star is similar to those of Jupiter and Mercury, respectively.
Conclusions. The robust and the probable companions of Ό Sco are naturally added to the giant 10.9 M planet recently discovered by BEAST around the binary b Cen system. While these objects are slightly more massive than the deuterium burning limit, their properties are similar to those of giant planets around less massive stars and they are better reproduced by assuming that they formed under a planet-like, rather than a star-like scenario. Irrespective of the (needed) confirmation of the inner companion, Ό Sco is the first star that would end its life as a supernova that hosts such a system. The tentative high frequency of BEAST discoveries is unexpected, and it shows that systems with giant planets or small-mass brown dwarfs can form around B stars. When putting this finding in the context of core accretion and gravitational instability formation scenarios, we conclude that the current modeling of both mechanisms is not able to produce this kind of companion. The completion of BEAST will pave the way for the first time to an extension of these models to intermediate and massive stars