Spin–Orbit Alignment of the β Pictoris Planetary System

Kraus, Stefan; Bouquin, J.-B. Le; Kreplin, Alexander; Davies, Claire L.; Hone, Edward; Monnier, John D.; Gardner, Tyler; Kennedy, Grant M.; Hinkley, Sasha

doi:10.3847/2041-8213/ab9d27

Cited by 32 publications

(36 citation statements)

References 41 publications

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“…Firstly, the knowledge of the mass of b that comes from the spectrum of the atmosphere (GRAVITY Collaboration 2020): 15.4±3.0 M Jup . Secondly, an estimation of the stellar mass of 1.75 ± 0.05 M (Kraus et al 2020).…”

Section: The Orbit Of β Pic Cmentioning

confidence: 99%

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Direct confirmation of the radial-velocity planetβPictoris c

Nowak¹,

Lacour²,

Lagrange³

et al. 2020

A&A

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Context. Methods used to detect giant exoplanets can be broadly divided into two categories: indirect and direct. Indirect methods are more sensitive to planets with a small orbital period, whereas direct detection is more sensitive to planets orbiting at a large distance from their host star. This dichotomy makes it difficult to combine the two techniques on a single target at once. Aims. Simultaneous measurements made by direct and indirect techniques offer the possibility of determining the mass and luminosity of planets and a method of testing formation models. Here, we aim to show how long-baseline interferometric observations guided by radial-velocity can be used in such a way. Methods. We observed the recently-discovered giant planet β Pictoris c with GRAVITY, mounted on the Very Large Telescope Interferometer. Results. This study constitutes the first direct confirmation of a planet discovered through radial velocity. We find that the planet has a temperature of T = 1250 ± 50 K and a dynamical mass of M = 8.2 ± 0.8 MJup. At 18.5 ± 2.5 Myr, this puts β Pic c close to a ‘hot start’ track, which is usually associated with formation via disk instability. Conversely, the planet orbits at a distance of 2.7 au, which is too close for disk instability to occur. The low apparent magnitude (MK = 14.3 ± 0.1) favours a core accretion scenario. Conclusions. We suggest that this apparent contradiction is a sign of hot core accretion, for example, due to the mass of the planetary core or the existence of a high-temperature accretion shock during formation.

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Section: The Orbit Of β Pic Cmentioning

confidence: 99%

“…Their inclinations are 88.99 ± 0.01 • and 89.17 ± 0.50 • . This means that the two planets are co-planar to within less than a degree, perpendicular from the angular momentum vector of the star (Kraus et al 2020). The eccentricity of c from radial velocity alone is 0.29 ± 0.05 (Lagrange et al 2020).…”

Section: The Orbit Of β Pic Cmentioning

confidence: 99%

Direct confirmation of the radial-velocity planetβPictoris c

Nowak¹,

Lacour²,

Lagrange³

et al. 2020

A&A

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“…In this respect, β Pic b offers a particularly favorable geometry for the detection of transiting moons. If it has a close-in moon system aligned with the starplanet inclination of 89° (Kraus et al 2020), transits are guaranteed. For the favorable case of an Earth-mass moon with a H/He envelope, the transit signals would have an amplitude of about 2%, which might be barely detectable with existing ground-based high-contrast imaging instrumentation.…”

Section: Substellar Variabilitymentioning

confidence: 99%

On the Detection of Exomoons Transiting Isolated Planetary-mass Objects

Limbach

Vos

Winn

et al. 2021

ApJL

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All-sky imaging surveys have identified several dozen isolated planetary-mass objects (IPMOs) far away from any star. Here we examine the prospects for detecting transiting moons around these objects. We expect transiting moons to be common, occurring around 10%-15% of IPMOs, given that close-orbiting moons have a high geometric transit probability and are expected to be a common outcome of giant planet formation. The IPMOs offer an advantage over other directly imaged planets in that high-contrast imaging is not necessary to detect the photometric transit signal. For at least 30 (>50%) of the currently known IPMOs, observations of a single transit with the James Webb Space Telescope would have low enough forecast noise levels to allow for the detection of an Io-or Titan-like moon. The intrinsic variability of the IPMOs will be an obstacle. Using archival time-series photometry of IPMOs with the Spitzer Space Telescope as a proof of concept, we found evidence for a fading event of 2MASS J1119-1137 AB that might have been caused by intrinsic variability but is also consistent with a single transit of a habitable-zone 1.7 R ⊕ exomoon. Although the interpretation of this particular event is inconclusive, the characteristics of the data and the candidate signal suggest that Earth-sized habitable-zone exomoons around IPMOs are detectable with existing instrumentation.Unified Astronomy Thesaurus concepts: Natural satellites (Extrasolar) (483); Free floating planets (549); Transits (1711); Exoplanets (498); Habitable zone (696)

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“…The obliquity of β Pic b is not known, although a measurement of rotational broadening by Snellen et al (2014) implies that the planet is not being viewed pole on. Given that the four gas giant planets in the Solar system have a range of obliquities from 3 degrees to 98 degrees, it is reasonable to assume that the obliquity of β Pic b is unconstrained, and that the angle between the rotational axis of the planet and its orbital plane is similarly unconstrained, although it is worth noting that the spin axis of the star and the orbit of β Pic b are coaligned within measurement errors (Kraus et al 2020). One might argue that any CPD would be coplanar with the planet's orbital plane, but simulations by (Martin et al 2020) show that CPDs with small initial tilts can have a tilt instability increase its tilt and possible move them into our range of detection.…”

Section: Circumplanetary Disk Modelmentioning

confidence: 99%

The β Pictoris b Hill sphere transit campaign

Kenworthy

Mellon

Bailey

et al. 2021

A&A

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Aims. Photometric monitoring of β Pic in 1981 showed anomalous fluctuations of up to 4% over several days, consistent with foreground material transiting the stellar disk. The subsequent discovery of the gas giant planet β Pic b and the predicted transit of its Hill sphere to within a 0.1 au projected separation of the planet provided an opportunity to search for the transit of a circumplanetary disk (CPD) in this 21 ± 4 Myr-old planetary system. We aim to detect, or put an upper limit on, the density and nature of the material in the circumplanetary environment of the planet via the continuous photometric monitoring of the Hill sphere transit that occurred in 2017 and 2018. Methods. Continuous broadband photometric monitoring of β Pic requires ground-based observatories at multiple longitudes to provide redundancy and to provide triggers for rapid spectroscopic follow-up. These include the dedicated β Pic monitoring bRing observatories in Sutherland and Siding Springs, the ASTEP400 telescope at Concordia, and the space observatories BRITE and the Hubble Space Telescope (HST). We search the combined light curves for evidence of short-period transient events caused by rings as well as for longer-term photometric variability due to diffuse circumplanetary material. Results. We find no photometric event that matches with the event seen in November 1981, and there is no systematic photometric dimming of the star as a function of the Hill sphere radius. Conclusions. We conclude that the 1981 event was not caused by the transit of a CPD around β Pic b. The upper limit on the long-term variability of β Pic places an upper limit of 1.8 × 1022 g of dust within the Hill sphere (comparable to the ~100 km radius asteroid 16 Psyche). Circumplanetary material is either condensed into a disk that does not transit β Pic, condensed into a disk with moons that has an obliquity that does not intersect with the path of β Pic behind the Hill sphere, or is below our detection threshold. This is the first time that a dedicated international campaign has mapped the Hill sphere transit of an extrasolar gas giant planet at 10 au.

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Spin–Orbit Alignment of the β Pictoris Planetary System

Cited by 32 publications

References 41 publications

Direct confirmation of the radial-velocity planetβPictoris c

Direct confirmation of the radial-velocity planetβPictoris c

On the Detection of Exomoons Transiting Isolated Planetary-mass Objects

The β Pictoris b Hill sphere transit campaign

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