15 research outputs found
Resolved near-UV hydrogen emission lines at 40-Myr super-Jovian protoplanet Delorme 1 (AB)b: Indications of magnetospheric accretion
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.Comment: Published in A&A 669, L12, 11 pages, abbreviated abstrac
Are Narrow-line Seyfert 1 Galaxies Powered by Low-mass Black Holes?
Narrow-line Seyfert 1 galaxies (NLS1s) are believed to be powered by the accretion of matter onto low-mass black
holes (BHs) in spiral host galaxies with BH masses MBH ∼ 106–108 Msun. However, the broadband spectral energy distribution of the γ-ray-emitting NLS1s are found to be similar to flat-spectrum radio quasars. This challenges our
current notion of NLS1s having low MBH. To resolve this tension of low MBH values in NLS1s, we fitted the
observed optical spectrum of a sample of radio-loud NLS1s (RL-NLS1s), radio-quiet NLS1s (RQ-NLS1s), and
radio-quiet broad-line Seyfert 1 galaxies (RQ-BLS1s) of ∼500 each with the standard Shakura–Sunyaev accretion
disk (AD) model. For RL-NLS1s we found a mean log(MBH,AD/Msun) of 7.98 ± 0.54. For RQ-NLS1s and RQ-BLS1s
we found mean log(MBH,AD/Msun) of 8.00 ± 0.43 and 7.90 ± 0.57, respectively. While the derived MBH,AD values of
RQ-BLS1s are similar to their virial masses, for NLS1s the derived MBH,AD values are about an order of magnitude
larger than their virial estimates. Our analysis thus indicates that NLS1s have MBH similar to RQ-BLS1s and their
available virial MBH values are underestimated, influenced by their observed relatively small emission line widths.
Considering the Eddington ratio as an estimation of the accretion rate and using MBH,AD, we found the mean accretion
rate of our RQ-NLS1s, RL-NLS1s, and RQ-BLS1s as 0.06, 0.05 and 0.05, respectively. Our results, therefore, suggest that NLS1s have BH masses and accretion rates that are similar to BLS1s.</p
BEAST detection of a brown dwarf and a low-mass stellar companion around the young bright B star HIP 81208
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 ( pc), young ( Myr),
bright (V= mag), 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 for the inner companion and
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.Comment: 18 pages, 14 figures, 5 tables Accepted for publication in the 10.
Planets and planetary systems section of A&
Constraints on the nearby exoplanet Eps Ind Ab from deep near/mid-infrared imaging limits
© ESO 2021. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1051/0004-6361/202140730The past decade has seen increasing efforts in detecting and characterising exoplanets by high contrast imaging in the near/mid-infrared, which is the optimal wavelength domain for studying old, cold planets. In this work, we present deep AO imaging observations of the nearby Sun-like star Ind A with NaCo () and NEAR (10-12.5 microns) instruments at VLT, in an attempt to directly detect its planetary companion whose presence has been indicated from radial velocity (RV) and astrometric trends. We derive brightness limits from the non-detection of the companion with both instruments, and interpret the corresponding sensitivity in mass based on both cloudy and cloud-free atmospheric and evolutionary models. For an assumed age of 5 Gyr for the system, we get detectable mass limits as low as 4.4 in NaCo and 8.2 in NEAR bands at 1.5\arcsec from the central star. If the age assumed is 1 Gyr, we reach even lower mass limits of 1.7 in NaCo and 3.5 in NEAR bands, at the same separation. However, based on the dynamical mass estimate (3.25 ) and ephemerides from astrometry and RV, we find that the non-detection of the planet in these observations puts a constraint of 2 Gyr on the lower age limit of the system. NaCo offers the highest sensitivity to the planetary companion in these observations, but the combination with the NEAR wavelength range adds a considerable degree of robustness against uncertainties in the atmospheric models. This underlines the benefits of including a broad set of wavelengths for detection and characterisation of exoplanets in direct imaging studies.Peer reviewe
A Window into the Cradle of Planets : Direct detection and characterisation of young sub-stellar objects using high-contrast tools
Ever since we first laid eyes on the twinkling lights in the night sky, our species began its age-old quest to understand how we came into existence as a planet and what the future holds for it. Most of the traditional formation theories of planets were anchored on the examples drawn from our own solar system. With the surprising and emerging trends among the yet incomplete exoplanet demographics, we are at the wake of a rigorous revision of our theoretical understanding of how planets form and evolve. To form accurate theories however, it is necessary to base them on a planet population that spans the complete range of parameter space not only in terms of its physical properties like mass and orbital separation, but also with respect to the type of stars that host these planets and their age. In this regard, direct detection, whereby you measure photons coming from the planet, helps one get closer to the whole picture since the ideal target population for this technique are young, giant planets in wide orbits that are generally difficult to observe with other detection techniques. Over the last few years, the sensitivity reached by direct imaging observations has seen tremendous improvement owing to the use of high-contrast tools like coronagraphy and adaptive optics. The development of high-resolution spectrographs together with advanced post-processing techniques have recently, for the first time, enabled witnessing planets while in the process of being born, helping us understand how they grow by devouring material from the planetary nursery — a mechanism known as accretion. This is an exciting era for planetary science, with many ongoing as well as planned future surveys with both ground and space-based telescopes dedicated to unravelling the mysteries surrounding the origin of planets. In this thesis, I provide an overview of direct detection as a tool to study sub-stellar objects – a categorisation that includes both planets and brown dwarfs, and whose blurred lines of distinction is a point of contention in astronomy today. I concentrate my discussion on two techniques, high-contrast imaging and high-resolution spectroscopy, both of which have proven significant in the race for planet detection and characterisation. Three scientific research works are carried out as a part of this thesis, using which I highlight the benefits of these techniques in constraining the physical properties of planets and brown dwarfs, as well as obtaining clues to their formation mechanism. In Paper I, I search for a Jupiter-like planet around a nearby Sun-like star that has long eluded imaging surveys, revealing its presence only via its influence on the parent star. I show how the brightness constraints at various separations and multiple wavelengths from the parent star help set a lower limit on the vaguely defined age of the system, in the absence of detection of the planet in our observations. In Paper II, I report the discovery of two low-mass companions to a massive, bright, young star, infer their orbital dynamics from multi-epoch imaging data, and constrain their physical properties using simultaneous low-resolution spectroscopy. In Paper III, I use a high-resolution spectrograph to observe for the first time, resolved Hydrogen and Helium emission lines from a young, isolated planetary-mass object in the midst of formation. Based on analysis of these line profiles, I obtain clues to the possible accretion mechanism at play in this nebulous cosmic phenomenon
High-Contrast Investigation of the ε Ind system
This licentiate thesis provides a broad introduction into the methodology of detecting and characterising exoplanets, with the main focus on the method of high-contrast imaging (HCI). Developments in theoretical knowledge as well as instrumentation have, in the past decade, pushed the boundaries of what HCI can achieve, both in terms of detection sensitivity and constraining planet properties. Direct imaging surveys in the near infrared (NIR) and longward wavelengths have proven particularly useful in detecting younger giant planets at wide orbital separations. The scientific work presented as part of this thesis is one such result of an imaging pursuit of the young giant planet, ϵ Ind Ab, which has long eluded NIR imaging surveys in the past, yet revealing its existence via radial velocity trends and astrometry of the parent star. It resides in the very interesting ϵ Ind stellar system, revolving around the primary star ϵ Ind A which is a Sun-like star only ∼12 light years away and visible in the night sky to the naked eye. With the combination of imaging data from two mid infrared (MIR) instruments, advanced post-processing techniques as well as comparative analysis using different planet atmospheric models, this work was able to place tight constraints on the age of the system and mass of the planet, although no detection was achieved. The new constraints set a firm foundation for MIR imaging surveys for the planet in future, especially with the upcoming more sensitive, advanced instruments in the later half of the decade. MIR imaging surveys have gained increasing significance in the recent years, due to their ability to detect colder/ smaller planets. It plays an important role in covering the missing gaps in the planet parameter space, ultimately aiding in improving our knowledge on planet formation and evolution
High-Contrast Investigation of the ε Ind system
This licentiate thesis provides a broad introduction into the methodology of detecting and characterising exoplanets, with the main focus on the method of high-contrast imaging (HCI). Developments in theoretical knowledge as well as instrumentation have, in the past decade, pushed the boundaries of what HCI can achieve, both in terms of detection sensitivity and constraining planet properties. Direct imaging surveys in the near infrared (NIR) and longward wavelengths have proven particularly useful in detecting younger giant planets at wide orbital separations. The scientific work presented as part of this thesis is one such result of an imaging pursuit of the young giant planet, ϵ Ind Ab, which has long eluded NIR imaging surveys in the past, yet revealing its existence via radial velocity trends and astrometry of the parent star. It resides in the very interesting ϵ Ind stellar system, revolving around the primary star ϵ Ind A which is a Sun-like star only ∼12 light years away and visible in the night sky to the naked eye. With the combination of imaging data from two mid infrared (MIR) instruments, advanced post-processing techniques as well as comparative analysis using different planet atmospheric models, this work was able to place tight constraints on the age of the system and mass of the planet, although no detection was achieved. The new constraints set a firm foundation for MIR imaging surveys for the planet in future, especially with the upcoming more sensitive, advanced instruments in the later half of the decade. MIR imaging surveys have gained increasing significance in the recent years, due to their ability to detect colder/ smaller planets. It plays an important role in covering the missing gaps in the planet parameter space, ultimately aiding in improving our knowledge on planet formation and evolution