Resolved near-UV hydrogen emission lines at 40-Myr super-Jovian protoplanet Delorme 1 (AB)b
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Description
Context. Accretion at planetary-mass companions (PMCs) suggests the presence of a protoplanetary disc in the system, likely accom-
panied by a circumplanetary disc. High-resolution spectroscopy of accreting PMCs is very difficult due to their proximity to bright
host stars. For well-separated companions, however, such spectra are feasible and they are unique windows into accretion.
Aims. We have followed up on our observations of the 40-Myr, and still accreting, circumbinary 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.
Methods. We have used the UVES spectrograph on the ESO VLT/UT2 to obtain Rλ ≈ 50 000 spectroscopy, at 3300–4520 Å, of
Delorme 1 (AB)b. 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.
Results. 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 (Hγ, Hδ, Hϵ, 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 of ˙M = 2 × 10−8 MJ yr−1. The lines are asym-
metric and are well described by sums of narrow and broad components with different velocity shifts. The overall line shapes are best
explained by a pre-shock velocity of v0 = 170 ± 30 km s−1, implying a planetary mass of MP = 13 ± 5 MJ, and number densities of
n0 & 1013 cm−3 or n0 ∼ 1011 cm−3. 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 line profiles.
Conclusions. High-resolution spectroscopy offers the opportunity to resolve line profiles, which are crucial for studying the accre-
tion 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 (a) 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.
panied by a circumplanetary disc. High-resolution spectroscopy of accreting PMCs is very difficult due to their proximity to bright
host stars. For well-separated companions, however, such spectra are feasible and they are unique windows into accretion.
Aims. We have followed up on our observations of the 40-Myr, and still accreting, circumbinary 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.
Methods. We have used the UVES spectrograph on the ESO VLT/UT2 to obtain Rλ ≈ 50 000 spectroscopy, at 3300–4520 Å, of
Delorme 1 (AB)b. 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.
Results. 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 (Hγ, Hδ, Hϵ, 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 of ˙M = 2 × 10−8 MJ yr−1. The lines are asym-
metric and are well described by sums of narrow and broad components with different velocity shifts. The overall line shapes are best
explained by a pre-shock velocity of v0 = 170 ± 30 km s−1, implying a planetary mass of MP = 13 ± 5 MJ, and number densities of
n0 & 1013 cm−3 or n0 ∼ 1011 cm−3. 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 line profiles.
Conclusions. High-resolution spectroscopy offers the opportunity to resolve line profiles, which are crucial for studying the accre-
tion 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 (a) 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.
Date of Publication
2023
Publication Type
Article
Subject(s)
Language(s)
en
Contributor(s)
Ringqvist, Simon C. | |
Viswanath, Gayathri | |
Aoyama, Yuhiko | |
Janson, Markus | |
Brandeker, Alexis |
Additional Credits
Series
Astronomy and astrophysics
Publisher
EDP Sciences
ISSN
0004-6361
Access(Rights)
open.access