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 (148.7
−1.3
+1.5
pc), young (17
−4
+3
Myr), bright (
V
= 6.632 ± 0.006 mag), 2.58 ± 0.06
M
⊙
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. Our analysis of the photometry obtained gives mass estimates of 67
−7
+6
M
J
for the inner companion and 0.135
−0.013
+0.010
M
⊙
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.
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
M
J
yr
−1
, gas extinction is negligible for spherical or polar inflow and at most
A
H
α
≲ 0.5 mag for magnetospheric accretion. Up to
Ṁ
≈ 3 × 10
−4
M
J
yr
−1
, the gas contributes
A
H
α
≲ 4 mag. This contribution decreases with mass. We estimate realistic dust opacities at H
α
to be
κ
~ 0.01–10 cm
2
g
−1
, which is 10–10
4
times lower than in the interstellar medium. Extinction flattens the
L
H
α
–
Ṁ
relationship, which becomes non-monotonic with a maximum luminosity
L
H
α
~ 10
−4
L
⊙
towards
Ṁ
≈ 10
−4
M
J
yr
−1
for a planet mass ~10
M
J
. 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
~ 10
5
) can provide (complex) constraints on the thermal and dynamical structure of the accretion flow.
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 (5−20 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
μ
2
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 μ
2
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
J
)at a projected separation of 290 ± 10 au, and a probable second similar object (18.5 ± 1.5
M
J
) 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
μ
2
Sco are naturally added to the giant 10.9
M
J
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,
μ
2
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.
Context.
Accretion at planetary-mass companions (PMCs) suggests the presence of a protoplanetary disc in the system, likely accompanied 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
R
λ
≈ 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 (H
γ
, H
δ
, H
ϵ
, 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
Ṁ
= 2 × 10
−8
M
J
yr
−1
. The lines are asymmetric 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
v
0
= 170 ± 30 km s
−1
, implying a planetary mass of
M
P
= 13 ± 5
M
J
, and number densities of
n
0
≳ 10
13
cm
−3
or
n
0
∼ 10
11
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 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 (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.
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
β
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 є 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
α
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.
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, O
I
λλ
6300, 6363, N
II
λλ
6548, 6583, H
α
, and S
II
λλ
6716, 6730 that are believed to be associated with jets and magnetically driven winds in the inner disks, due to the proximity to the star, as suggested in previous works from the literature. With a resolution of 0.025 × 0.025 arcsec
2
, we aim to derive the position angle of the outflow/jet (PA
outflow/jet
) that is connected with the inner disk. We then compare it with the position angle of the dust (PA
dust
) obtained from previous constraints for the outer disk. We also carry out a simple analysis of the kinematics and width of the lines and we estimate the mass-loss rate based on the O
I
λ
6300 line for five T Tauri stars.
Methods
. Observations were carried out with the optical integral field spectrograph of the Multi Unit Spectroscopic Explorer (MUSE), at the Very Large Telescope (VLT). The instrument spatially resolves the forbidden lines, providing a unique capability to access the spatial extension of the outflows/jets that make the estimate of the PA
outflow/jet
possible from a geometrical point of view.
Results
. The forbidden emission lines analyzed here have their origin at the inner parts of the protoplanetary disk. From the maximum intensity emission along the outflow/jet in DL Tau, CI Tau, DS Tau, IP Tau, and IM Lup, we were able to reliably measure the PA
outflow/jet
for most of the identified lines. We found that our estimates agree with PA
dust
for most of the disks. These estimates depend on the signal-to-noise level and the collimation of the outflow (jet). The outflows/jets in CIDA 9, GO Tau, and GW Lup are too compact for a PA
outflow/jet
to be estimated. Based on our kinematics analysis, we confirm that DL Tau and CI Tau host a strong outflow/jet with line-of-sight velocities much greater than 100 km s
−1
, whereas DS Tau, IP Tau, and IM Lup velocities are lower and their structures encompass low-velocity components to be more associated with winds. Our estimates for the mass-loss rate,
Ṁ
loss
, range between (1.1–6.5) × 10
−7
–10
−8
M
⊙
yr
−1
for the disk-outflow/jet systems analyzed here.
Conclusions
. The outflow/jet systems analyzed here are aligned within around 1° between the inner and outer disk. Further observations are needed to confirm a potential misalignment in IM Lup.
Planet formation occurs around a wide range of stellar masses and stellar system architectures
. 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
until a turnover point at 1.9 solar masses (M
), above which the frequency rapidly decreases
. This could potentially imply that planet formation is impeded around more massive stars, and that giant planets around stars exceeding 3 M
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
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
, but might have formed elsewhere and arrived to its present location through dynamical interactions, or might have formed via gravitational instability.
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.
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.
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 (\(148.7^{+1.5}_{-1.3}\) pc), young (\(17^{+3}_{-4}\) Myr), bright (V=\(6.632\pm0.006\) mag), \(2.58\pm0.06~ M_{\odot}\) 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 \(67^{+6}_{-7}~M_J\) for the inner companion and \(0.135^{+0.010}_{-0.013}~M_{\odot}\) 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.
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