High-resolution ALMA and HST images of q1 Eri: an asymmetric debris disc with an eccentric Jupiter

J B Lovell,L Matrà,M C Wyatt,Q Kral,J Krist,B Dent,T D Pearce,S Marino,M A Macgregor,D Wilner,G M Kennedy,K Stapelfeldt,O Panić

doi:10.1093/mnras/stab1678

Abstract

ABSTRACT We present Atacama Large Millimetre/sub-Millimetre Array (ALMA) 1.3 and 0.86 mm observations of the nearby (17.34 pc) F9V star q1 Eri (HD 10647, HR 506). This system, with age ∼1.4 Gyr, hosts a ∼2 au radial velocity planet and a debris disc with the highest fractional luminosity of the closest 300 FGK type stars. The ALMA images, with resolution ∼0${_{.}^{\prime\prime}}$5, reveal a broad (34–134 au) belt of millimetre emission inclined by 76.7 ± 1.0 degrees with maximum brightness at 81.6 ± 0.5 au. The images reveal an asymmetry, with higher flux near the south-west ansa, which is also closer to the star. Scattered light observed with the Hubble Space Telescope is also asymmetric, being more radially extended to the north-east. We fit the millimetre emission with parametric models and place constraints on the disc morphology, radius, width, dust mass, and scale height. We find that the south-west ansa asymmetry is best fitted by an extended clump on the inner edge of the disc, consistent with perturbations from a planet with mass $8\, M_{\oplus } {-} 11\, M_{\rm Jup}$ at ∼60 au that may have migrated outwards, similar to Neptune in our Solar system. If the measured vertical aspect ratio of h = 0.04 ± 0.01 is due to dynamical interactions in the disc, then this requires perturbers with sizes &gt;1200 km. We find tentative evidence for a 0.86 mm excess within 10 au, $70{\pm }22\, \mu$Jy, that may be due to an inner planetesimal belt. We find no evidence for CO gas, but set an upper bound on the CO gas mass of 4 × 10−6 M⊕ ($3\sigma$), consistent with cometary abundances in the Solar system.

Highlights

The first detections of exoplanetary systems were made a few decades ago (Aumann et al 1984; Harper et al 1984; Wolszczan & Frail 1992; Mayor & Queloz 1995)
We have found four significant observational constraints that we can place on the q1 Eri debris disc, the first 3 from Atacama Large Millimetre/sub-Millimetre Array (ALMA) (O1-3) and the fourth from Hubble Space Telescope (HST) (O4), which will be used to constrain our modelling in §4 and discussed further in §5: O1 - Broad Structure: q1 Eri has a bright, broad disc, with a position angle PA=57.0±1.0◦, and an inclination i=76.7±1.0◦
From previous ALMA modelling of debris discs, it has been shown that the CASA routine statwt does not provide an accurate measure of the absolute uncertainties on visibility measurements, it does provide a good estimate of the relative errors between visibilities

Summary

Introduction

The first detections of exoplanetary systems (systems with planets and/or planetesimal belts) were made a few decades ago (Aumann et al 1984; Harper et al 1984; Wolszczan & Frail 1992; Mayor & Queloz 1995). The planets that have been observed around other stars fit into a few different classes based on their masses, radii and semimajor axes. These include objects such as short period super Earths found during transits, outer giants observed by direct imaging, and exo-Jupiters discovered by radial velocity measurements. It might be expected that the formation mechanism of different planets is reflected in the properties of their debris discs, and recent studies have explored such connections for Super Earth systems like 61 Vir (Marino et al 2017), and for systems with known outer giants like HR 8799 and Beta Pic (see Booth et al 2016; Matrà et al 2017), and for populations of directly-imaged giant planets (see Meshkat et al 2017)

Results

Discussion

Conclusion