Strong H<i>α</i> emission and signs of accretion in a circumbinary planetary mass companion from MUSE

Eriksson, Simon; Torres, Ruben Asensio; Janson, Markus; Aoyama, Yuhiko; Marleau, Gabriel-Dominique; Bonnefoy, M.; Petrus, Simon

doi:10.1051/0004-6361/202038131

Cited by 40 publications

(73 citation statements)

References 59 publications

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“…Finally, another way to look for these perturbers is to detect hydrogen emission lines, such as Hα, originating in the shockheated gas during the accretion of disk material (Aoyama & Ikoma 2019). If detected, this emission constitutes the main observational signature of the ongoing formation of a substellar object (Eriksson et al 2020). Observations of PPDs with SPHERE/ZIMPOL and MUSE have so far been unable to detect planetary-mass companions around PPD hosts other than the pair around PDS 70, despite reaching potential sensitivities down to 1 M Jup (Haffert et al 2019;Zurlo et al 2020).…”

Section: Potential For Future Detectionmentioning

confidence: 99%

Perturbers: SPHERE detection limits to planetary-mass companions in protoplanetary disks

Asensio-Torres

Henning

Cantalloube

et al. 2021

A&A

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The detection of a wide range of substructures such as rings, cavities, and spirals has become a common outcome of high spatial resolution imaging of protoplanetary disks, both in the near-infrared scattered light and in the thermal millimetre continuum emission. The most frequent interpretation of their origin is the presence of planetary-mass companions perturbing the gas and dust distribution in the disk (perturbers), but so far the only bona fide detection has been the two giant planets carving the disk around PDS 70. Here, we present a sample of 15 protoplanetary disks showing substructures in SPHERE scattered-light images and a homogeneous derivation of planet detection limits in these systems. To obtain mass limits we rely on different post-formation luminosity models based on distinct formation conditions, which are critical in the first million years of evolution. We also estimate the mass of these perturbers through a Hill radius prescription and a comparison to ALMA data. Assuming that one single planet carves each substructure in scattered light, we find that more massive perturbers are needed to create gaps within cavities than rings, and that we might be close to a detection in the cavities of RX J1604.3-2130A, RX J1615.3-3255, Sz Cha, HD 135344B, and HD 34282. We reach typical mass limits in these cavities of 3–10 MJup. For planets in the gaps between rings, we find that the detection limits of SPHERE high-contrast imaging are about an order of magnitude away in mass, and that the gaps of PDS 66 and HD 97048 seem to be the most promising structures for planet searches. The proposed presence of massive planets causing spiral features in HD 135344B and HD 36112 are also within SPHERE’s reach assuming hot-start models. These results suggest that the current detection limits are able to detect hot-start planets in cavities, under the assumption that they are formed by a single perturber located at the centre of the cavity. More realistic planet mass constraints would help to clarify whether this is actually the case, which might indicate that perturbers are not the only way of creating substructures.

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Section: Potential For Future Detectionmentioning

confidence: 99%

Perturbers: SPHERE detection limits to planetary-mass companions in protoplanetary disks

Asensio-Torres

Henning

Cantalloube

et al. 2021

A&A

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“…Evidence for circumplanetary accretion disks around young (<10 Myr) giant planets has been seen in both planet formation simulations (e.g., Lubow et al 1999;D'Angelo et al 2002) and observations (e.g., Bowler et al 2011;Christiaens et al 2019). However, recent detections of long-lived accretion disks ("Peter-Pan disks") around planetary-mass, brown dwarf, and M dwarf objects with ages of ∼20-55 Myr (Eriksson et al 2020;Boucher et al 2016;Murphy et al 2018;Lee et al 2020;Silverberg et al 2020) suggest that a disk around HD 206893 B could be plausible if its age is at the lower end of the range of ∼50-700 Myr predicted by Delorme et al (2017). The interferometric visibilities measured by GRAVITY agree with the SPHERE K1-and K2-band photometry within 11.5% and 7.7%, respectively, and we find no dependence of the visibility as a function of the baseline length.…”

Section: Free Retrievalsmentioning

confidence: 99%

GRAVITY K-band spectroscopy of HD 206893 B

Kammerer

Lacour

Stolker

et al. 2021

A&A

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Context. Near-infrared interferometry has become a powerful tool for studying the orbital and atmospheric parameters of substellar companions. Aims. We aim to reveal the nature of the reddest known substellar companion HD 206893 B by studying its near-infrared colors and spectral morphology and by investigating its orbital motion. Methods. We fit atmospheric models for giant planets and brown dwarfs and perform spectral retrievals with petitRADTRANS and ATMO on the observed GRAVITY, SPHERE, and GPI spectra of HD 206893 B. To recover its unusual spectral features, first and foremost its extremely red near-infrared color, we include additional extinction by high-altitude dust clouds made of enstatite grains in the atmospheric model fits. However, forsterite, corundum, and iron grains predict similar extinction curves for the grain sizes considered here. We also infer the orbital parameters of HD 206893 B by combining the ~100 μas precision astrometry from GRAVITY with data from the literature and constrain the mass and position of HD 206893 C based on the Gaia proper motion anomaly of the system. Results. The extremely red color and the very shallow 1.4 μm water absorption feature of HD 206893 B can be fit well with the adapted atmospheric models and spectral retrievals. By comparison with AMES-Cond evolutionary tracks, we find that only some atmosphericmodels predict physically plausible objects. Altogether, our analysis suggests an age of ~ 3–300 Myr and a mass of ~ 5–30 MJup for HD 206893 B, which is consistent with previous estimates but extends the parameter space to younger and lower-mass objects. The GRAVITY astrometry points to an eccentric orbit (e = 0.29−0.11+0.06) with a mutual inclination of <34.4 deg with respectto the debris disk of the system. Conclusions. While HD 206893 B could in principle be a planetary-mass companion, this possibility hinges on the unknown influence of the inner companion on the mass estimate of 10−4+5 MJup from radial velocity and Gaia as well as a relatively small but significant Argus moving group membership probability of ~ 61%. However, we find that if the mass of HD 206893 B is <30 MJup, then the inner companion HD 206893 C should have a mass between ~ 8–15 MJup. Finally, further spectroscopic or photometric observations at higher signal-to-noise and longer wavelengths are required to learn more about the composition and dust cloud properties of HD 206893 B.

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“…Thanks to instrumentation advances (VLT/SPHERE, VLT/MUSE, LBT/LBTI, Magellan/MagAO; Bacon et al 2010;Close et al 2014a,b;Schmid et al 2017Schmid et al , 2018, a handful of low-mass companions to young stars have been detected and explored that (possibly) show signs of ongoing accretion: LkCa 15 b (Sallum et al 2015; but see also Mendigutía et al 2018;Currie et al 2019), PDS 70 b and c (Keppler et al 2018;Müller et al 2018;Wagner et al 2018;Haffert et al 2019;Zhou et al 2021), and Delorme 1 (AB)b (Eriksson et al 2020). On the other hand, recent surveys searching for further accreting planets through their H α signal have returned null results, from five (Cugno et al 2019) and eleven (Zurlo et al 2020) different sources 1 (see also Xie et al 2020).…”

Section: Current and Future Instrumentationmentioning

confidence: 99%

“…However, in cases where a companion is a few arcseconds (i.e. a few hundreds of astronomical units at 150 pc) away and its H α line is reasonably strong, it could still be possible to get a spatially resolved signature with UVES, Delorme 1 (AB)b (Eriksson et al 2020) being one potential example.…”

Section: Current and Future Instrumentationmentioning

confidence: 99%

Accreting protoplanets: Spectral signatures and magnitude of gas and dust extinction at Hα

Marleau

Aoyama

Kuiper

et al. 2021

A&A

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Context. Accreting planetary-mass objects have been detected at H α, but targeted searches have mainly resulted in non-detections. Accretion tracers in the planetary-mass regime could originate from the shock itself, making them particularly susceptible to extinction by the accreting material. High-resolution (R > 50 000) spectrographs operating at H α should soon enable one to study how the incoming material shapes the line profile. Aims. We calculate how much the gas and dust accreting onto a planet reduce the H α flux from the shock at the planetary surface and how they affect the line shape. We also study the absorption-modified relationship between the H α luminosity and accretion rate. Methods. We computed the high-resolution radiative transfer of the H α line using a one-dimensional velocity–density–temperature structure for the inflowing matter in three representative accretion geometries: spherical symmetry, polar inflow, and magnetospheric accretion. For each, we explored the wide relevant ranges of the accretion rate and planet mass. We used detailed gas opacities and carefully estimated possible dust opacities. Results. At accretion rates of Ṁ ≲ 3 × 10−6 MJ yr−1, gas extinction is negligible for spherical or polar inflow and at most AH α ≲ 0.5 mag for magnetospheric accretion. Up to Ṁ ≈ 3 × 10−4 MJ yr−1, the gas contributes AH α ≲ 4 mag. This contribution decreases with mass. We estimate realistic dust opacities at H α to be κ ~ 0.01–10 cm2 g−1, which is 10–104 times lower than in the interstellar medium. Extinction flattens the LH α –Ṁ relationship, which becomes non-monotonic with a maximum luminosity LH α ~ 10−4 L⊙ towards Ṁ ≈ 10−4 MJ yr−1 for a planet mass ~10 MJ. In magnetospheric accretion, the gas can introduce features in the line profile, while the velocity gradient smears them out in other geometries. Conclusions. For a wide part of parameter space, extinction by the accreting matter should be negligible, simplifying the interpretation of observations, especially for planets in gaps. At high Ṁ, strong absorption reduces the H α flux, and some measurements can be interpreted as two Ṁ values. Highly resolved line profiles (R ~ 105) can provide (complex) constraints on the thermal and dynamical structure of the accretion flow.

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Strong Hα emission and signs of accretion in a circumbinary planetary mass companion from MUSE

Cited by 40 publications

References 59 publications

Perturbers: SPHERE detection limits to planetary-mass companions in protoplanetary disks

Perturbers: SPHERE detection limits to planetary-mass companions in protoplanetary disks

GRAVITY K-band spectroscopy of HD 206893 B

Accreting protoplanets: Spectral signatures and magnitude of gas and dust extinction at Hα

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