SPHERE adaptive optics performance for faint targets

Jones, M. I.; Milli, J.; Blanchard, Israel; Wahhaj, Z.; Rosa, Robert J. De; Romero, C.; Ihanec, N.

doi:10.1051/0004-6361/202243820

Cited by 6 publications

(3 citation statements)

References 23 publications

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“…We accounted for the degradation in contrast performance for fainter stars (e.g. Jones et al 2022) by scaling the contrast curve by the square root of the H-band flux ratio between the Ba star host and HR 8799, the star observed by Wahhaj et al (2021) to measure the contrast curve.…”

Section: Future Observational Prospects: Direct Imaging Of These Whit...mentioning

confidence: 99%

Barium and related stars, and their white-dwarf companions

Escorza

Rosa

2023

A&A

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Context. Masses are one of the most difficult stellar properties to measure. In the case of the white-dwarf (WD) companions of Barium (Ba) stars, the situation is worse. These stars are dim, cool, and difficult to observe via direct methods. However, Ba stars were polluted by the asymptotic giant branch (AGB) progenitors of these WDs with matter rich in heavy elements, and the properties of their WD companions contain key information about binary interaction processes involving AGB stars and about the slow neutron capture process (s-process) of nucleosynthesis. Aims. With this study, we aim to determine accurate and assumption-free masses for the WD companions of as many Ba stars as possible. We want to provide new observational constraints that can help us learn about the formation and evolution of these post-interaction binary systems and about the nucleosythesis processes that took place in the interiors of their AGB progenitors. Methods. We combined archival radial-velocity data with HIPPARCOS and Gaia astrometry using the software package ORVARA, a code designed to simultaneously fit a single Keplerian model to any combination of these types of data using a parallel-tempering Markov chain Monte Carlo method. We adopted Gaussian priors for the Ba star masses and for the parallaxes, and assumed uninformative priors for the orbital elements and the WD masses. Results. We determined new orbital inclinations and companion masses for 60 Ba star systems. These results include a couple of new orbits and several improved orbits for the longest-period systems. Additionally, we unravelled a new triple system that was not known before and constrained the orbits and the masses of the two companions. Conclusions. The WD mass distribution presented in this work is compatible with that of field WDs and with the distributions published before for Ba star companions. A few WD companions have masses higher than 0.8 M⊙, considering 1-σ uncertainties. This indicates that they might come from AGB stars that are more massive than 3 M⊙. These masses are higher than what the abundance ratios on Ba star atmospheres and theoretical models of the s-process of nucleosynthesis seem to expect, raising interesting questions about the formation of these systems.

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Section: Future Observational Prospects: Direct Imaging Of These Whit...mentioning

confidence: 99%

Barium and related stars, and their white-dwarf companions

Escorza

Rosa

2023

A&A

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“…Given that DI-sNMF depends on the adaptive optics' control ring signals for data reduction in Sect. 3.2, this illustrates that the importance of the adaptive optics performance (e.g., Jones et al 2022) in producing the control ring for DI-sNMF data reduction.…”

Section: Rdi I Tot Detectability With Stellar Parametersmentioning

confidence: 75%

Protoplanetary disks in K_s-band total intensity and polarized light

Ren,

Benisty,

Ginski

et al. 2023

A&A

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Context. The diverse morphology among protoplanetary disks may result from planet-disk interactions, suggesting the presence of planets undergoing formation. The characterization of disks can provide information on the formation environments of planets. To date, most imaging campaigns have probed the polarized light from disks, which is only a fraction of the total scattered light and not very sensitive to planetary emission. Aims. We aim to observe and characterize protoplanetary disk systems in the near-infrared in both polarized and total intensity light to carry out an unprecedented study of the dust scattering properties of disks, as well as of any possible planetary companions. Methods. Using the star-hopping mode of the SPHERE instrument at the Very Large Telescope, we observed 29 young stars hosting protoplanetary disks and their reference stars in the Ks-band polarized light. We extracted disk signals in total intensity by removing stellar light using the corresponding reference star observations, by adopting the data imputation concept with sequential non-negative matrix factorization (DI-sNMF). For well-recovered disks in both polarized and total intensity light, we parameterized the polarization fraction phase functions using a scaled beta distribution. We investigated the empirical DI-sNMF detectability of disks using logistic regression. For systems with SPHERE data in the Y, J, and H bands, we have summarized their polarized color at an approximately 90° scattering angle. Results. We obtained high-quality disk images in total intensity for 15 systems and in polarized light for 23 systems. The total intensity detectability of disks primarily depends on the host star brightness, which determines adaptive-optics control ring imagery and thus stellar signals capture using DI-sNMF. The peak of polarization fraction tentatively correlates with the peak scattering angle, which could be reproduced using certain composition for compact dust, yet more detailed modeling studies are needed. Most of the disks are blue in polarized J – Ks color and the fact that they are relatively redder as stellar luminosity increases indicates larger scatterers. Conclusions. High-quality disk imagery in both total intensity and polarized light allows for disk characterizations in the polarization fraction. Combining these techniques reduces the confusion between the disk and planetary signals.

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“…Some of the detected structures have low S/N, in part due to low data quality in the H-band and the intrinsically faint signal in the K-band. The primary star in the SY Cha system is faint in the optical (Gmag = 12.53 ± 0.01, Gaia Collaboration 2018) and thus a challenging target for the adaptive optics system of SPHERE (see Jones et al 2022). During the H-band observation the tip-tilt stabilization had to be disabled, resulting in the star moving slightly behind the coronagraphic mask.…”

Section: Sy Chamentioning

confidence: 99%

The SPHERE view of the Chamaeleon I star-forming region

Ginski,

Garufi,

Benisty

et al. 2024

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The past few years have seen a revolution in the study of circumstellar disks. New instrumentation in the near-infrared and (sub)millimeter regimes have allowed us to routinely spatially resolve disks around young stars of nearby star-forming regions. As a result, we have found that substructures with scales of sim 10\,au in disks are common. We have also revealed a zoo of different morphologies, sizes, and luminosities that is as complex as the diversity of architectures found in evolved exoplanet systems. We study disk evolutionary trends as they appear in scattered light observations. Scattered light traces the micron-sized particles at the disk surface that are well coupled to the gas. This means that scattered light observations can be used to trace the distribution of the disk gas and its interaction with embedded perturbers. We used VLT/SPHERE to observe 20 systems in the Cha I cloud in polarized scattered light in the near-infrared. We combined the scattered light observations with existing literature data on stellar properties and with archival ALMA continuum data to study trends with system age and dust mass. We also connected resolved near-infrared observations with the spectral energy distributions of the systems. In 13 of the 20 systems included in this study we detected resolved scattered light signals from circumstellar dust. For the CR\,Cha, CT\,Cha, CV\,Cha, SY\,Cha, SZ\,Cha, and VZ\,Cha systems we present the first detailed descriptions of the disks in scattered light. The observations found typically smooth or faint disks, often with little substructure, with the notable exceptions of SZ\,Cha, which shows an extended multiple-ringed disk, and WW\,Cha, which shows interaction with the cloud environment. New high S/N K-band observations of the HD\,97048 system in our survey reveal a significant brightness asymmetry that may point to disk misalignment and subsequent shadowing of outer disk regions, possibly related to the suggested planet candidate in the disk. We resolve for the first time the stellar binary in the CS\,Cha system. Multiple wavelength observations of the disk around CS\,Cha have revealed that the system contains small, compact dust grains that may be strongly settled, consistent with numerical studies of circumbinary disks. We find in our sample that there is a strong anti-correlation between the presence of a (close) stellar companion and the detection of circumstellar material with five of our seven nondetections located in binary systems. We also find a correlation between disk mass, as inferred from millimeter observations, and the detection of scattered light signal. Finally, we find a tentative correlation between relative disk-to-star brightness in scattered light and the presence of a dust cavity in the inner (unresolved) disk, as traced by the system spectral energy distribution. At the same time, faint disks in our sample are generally younger than 2\,Myr.

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SPHERE adaptive optics performance for faint targets

Cited by 6 publications

References 23 publications

Barium and related stars, and their white-dwarf companions

Barium and related stars, and their white-dwarf companions

Protoplanetary disks in K_s-band total intensity and polarized light

The SPHERE view of the Chamaeleon I star-forming region

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SPHERE adaptive optics performance for faint targets

Cited by 6 publications

References 23 publications

Barium and related stars, and their white-dwarf companions

Barium and related stars, and their white-dwarf companions

Protoplanetary disks in Ks-band total intensity and polarized light

The SPHERE view of the Chamaeleon I star-forming region

Contact Info

Product

Resources

About

Protoplanetary disks in K_s-band total intensity and polarized light