scholarly journals The widest Hα survey of accreting protoplanets around nearby transition disks

2020 ◽  
Vol 633 ◽  
pp. A119 ◽  
Author(s):  
A. Zurlo ◽  
G. Cugno ◽  
M. Montesinos ◽  
S. Perez ◽  
H. Canovas ◽  
...  
Keyword(s):  
Speckle Pattern ◽  
Principal Component ◽  
Central Star ◽  
Solar Neighborhood ◽  
Very Large Telescope ◽  
Narrow Band Filter ◽  
Substellar Companions ◽  
Average Contrast ◽  
Differential Imaging ◽  
Transition Disks

Context. The mechanisms of planet formation are still under debate. We know little about how planets form, even if more than 4000 exoplanets have been detected to date. Recent investigations target the cot of newly born planets: the protoplanetary disk. At the first stages of their life, exoplanets still accrete material from the gas-rich disk in which they are embedded. Transitional disks are indeed disks that show peculiarities, such as gaps, spiral arms, and rings, which can be connected to the presence of substellar companions. Aims. To investigate what is responsible for these features, we selected all the known transitional disks in the solar neighborhood (<200 pc) that are visible from the southern hemisphere. We conducted a survey of 11 transitional disks with the SPHERE instrument at the Very Large Telescope. This is the largest Hα survey that has been conducted so far to look for protoplanets. The observations were performed with the Hα filter of ZIMPOL in order to target protoplanets that are still in the accretion stage. All the selected targets are very young stars, less than 20 Myr, and show low extinction in the visible. Methods. We reduced the ZIMPOL pupil stabilized data by applying the method of the angular spectral differential imaging (ASDI), which combines both techniques. The datacubes are composed of the Cnt_Hα and the narrow band filter Hα, which are taken simultaneously to permit the suppression of the speckle pattern. The principal component analysis method was employed for the reduction of the data. For each dataset, we derived the 5σ contrast limit and converted it in upper limits on the accretion luminosity. Results. We do not detect any new accreting substellar companions around the targeted transition disks down to an average contrast of 12 magnitudes at 0.′′2 from the central star. We have recovered the signal of the accreting M star companion around the star HD 142527. We have detected and resolved, for the first time in visible light, the quadruple system HD 98800. For every other system, we can exclude the presence of massive actively accreting companions, assuming that the accretion is not episodic and that the extinction is negligible. The mean accretion luminosity limit is 10−6 L⊙ at a separation of 0.′′2 from the host.

scholarly journals Searching for Hα emitting sources around MWC 758

2018 ◽  
Vol 613 ◽  
pp. L5 ◽  
Author(s):  
N. Huélamo ◽  
G. Chauvin ◽  
H. M. Schmid ◽  
S. P. Quanz ◽  
E. Whelan ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Mass Range ◽  
Position Angle ◽  
Central Star ◽  
Young Star ◽  
Upper Limit ◽  
T Tauri ◽  
Very Large Telescope ◽  
Accretion Rates ◽  
Differential Imaging

Context. MWC 758 is a young star surrounded by a transitional disk. The disk shows an inner cavity and spiral arms that could be caused by the presence of protoplanets. Recently, a protoplanet candidate has been detected around MWC 758 through high-resolution L′-band observations. The candidate is located inside the disk cavity at a separation of ~111 mas from the central star, and at an average position angle of ~165.5°. Aims. We aim at detecting accreting protoplanet candidates within the disk of MWC 758 through angular spectral differential imaging (ASDI) observations in the optical regime. In particular, we explore the emission at the position of the detected planet candidate. Methods. We have performed simultaneous adaptive optics observations in the Hα line and the adjacent continuum using SPHERE/ZIMPOL at the Very Large Telescope (VLT). Results. The data analysis does not reveal any Hα signal around the target. The derived contrast curve in the B_Ha filter allows us to derive a 5σ upper limit of ~7.6 mag at 111 mas, the separation of the previously detected planet candidate. This contrast translates into a Hα line luminosity of LHα ≲ 5×10−5 L⊙ at 111 mas. Assuming that LHα scales with Lacc as in classical T Tauri stars (CTTSs) as a first approximation, we can estimate an accretion luminosity of Lacc < 3.7 × 10−4 L⊙ for the protoplanet candidate. For the predicted mass range of MWC 758b, 0.5–5 MJup, this implies accretion rates smaller than Ṁ < 3.4 × (10−8−10−9)M⊙ yr−1, for an average planet radius of 1.1 RJup. Therefore, our estimates are consistent with the predictions of accreting circumplanetary accretion models for Rin = 1RJup. The ZIMPOL line luminosity is consistent with the Hα upper limit predicted by these models for truncation radii ≲3.2 RJup. Conclusions. The non-detection of any Hα emitting source in the ZIMPOL images does not allow us to unveil the nature of the L′ detected source. Either it is a protoplanet candidate or a disk asymmetry.

scholarly journals The search for disks or planetary objects around directly imaged companions: a candidate around DH Tauri B

2020 ◽  
Vol 641 ◽  
pp. A131
Author(s):  
C. Lazzoni ◽  
A. Zurlo ◽  
S. Desidera ◽  
D. Mesa ◽  
C. Fontanive ◽  
...  
Keyword(s):  
Ad Hoc ◽  
Direct Methods ◽  
Brown Dwarfs ◽  
Central Star ◽  
Formation Mechanisms ◽  
Sources Of Information ◽  
Substellar Objects ◽  
Extended Sources ◽  
Substellar Companions ◽  
Differential Imaging

Context. In recent decades, thousands of substellar companions have been discovered with both indirect and direct methods of detection. While the majority of the sample is populated by objects discovered using radial velocity and transit techniques, an increasing number have been directly imaged. These planets and brown dwarfs are extraordinary sources of information that help in rounding out our understanding of planetary systems. Aims. In this paper, we focus our attention on substellar companions detected with the latter technique, with the primary goal of investigating their close surroundings and looking for additional companions and satellites, as well as disks and rings. Any such discovery would shed light on many unresolved questions, particularly with regard to their possible formation mechanisms. Methods. To reveal bound features of directly imaged companions, whether for point-like or extended sources, we need to suppress the contribution from the source itself. Therefore, we developed a method based on the negative fake companion technique that first estimates the position in the field of view (FoV) and the flux of the imaged companion with high precision, then subtracts a rescaled model point spread function (PSF) from the imaged companion, using either an image of the central star or another PSF in the FoV. Next it performs techniques, such as angular differential imaging, to further remove quasi-static patterns of the star (i.e., speckle contaminants) that affect the residuals of close-in companions. Results. After testing our tools on simulated companions and disks and on systems that were chosen ad hoc, we applied the method to the sample of substellar objects observed with SPHERE during the SHINE GTO survey. Among the 27 planets and brown dwarfs we analyzed, most objects did not show remarkable features, which was as expected, with the possible exception of a point source close to DH Tau B. This candidate companion was detected in four different SPHERE observations, with an estimated mass of ~1MJup, and a mass ratio with respect to the brown dwarf of 1∕10. This binary system, if confirmed, would be the first of its kind, opening up interesting questions for the formation mechanism, evolution, and frequency of such pairs. In order to address the latter, the residuals and contrasts reached for 25 companions in the sample of substellar objects observed with SPHERE were derived. If the DH Tau Bb companion is real, the binary fraction obtained is ~7%, which is in good agreement with the results obtained for field brown dwarfs. Conclusions. While there may currently be many limitations affecting the exploration of bound features to directly imaged exoplanets and brown dwarfs, next-generation instruments from the ground and space (i.e., JWST, ELT, and LUVOIR) will be able to image fainter objects and, thus, drive the application of this technique in upcoming searches for exo-moons and circumplanetary disks.

Planet-disk interactions in HD 169142? Tracing ellipticity, structures, and offsets

2018 ◽  
Vol 14 (S345) ◽  
pp. 241-243
Author(s):  
Gesa H.-M. Bertrang ◽  
Henning Avenhaus
Keyword(s):  
Surface Brightness ◽  
Broad Band ◽  
Small Scale ◽  
High Contrast ◽  
Large Telescope ◽  
Very Large Telescope ◽  
Be Star ◽  
Scale Structures ◽  
Differential Imaging ◽  
Small Scale Structures

AbstractIn Bertrang et al. (2018), we present new data of the protoplanetary disk surrounding the Herbig Ae/Be star HD 169142 obtained in the very broad-band (VBB) with the Zurich imaging polarimeter (ZIMPOL), a subsystem of the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) at the Very Large Telescope (VLT). Our Polarimetric Differential Imaging (PDI) observations probe the disk as close as 0.″3 (3.5au) to the star and are able to trace the disk out to ~1.″08 (~126 au). We find an inner hole, a bright ring bearing substructures around ~0.″18 (21au), and an elliptically shaped gap stretching from 0.″25 to 0.″47 (29–55 au). Outside of 0.″47, the surface brightness drops off, discontinued only by a narrow annular brightness minimum at ~0.″63–0.″74 (74–87 au). These observations confirm features found in less-well resolved data as well as reveal yet undetected indications for planet-disk interactions, such as small-scale structures, star-disk offsets, and potentially moving shadows.

scholarly journals TRIDENT: An Infrared Differential Imaging Camera Optimized for the Detection of Methanated Substellar Companions

2005 ◽  
Vol 117 (833) ◽  
pp. 745-756 ◽  
Author(s):  
Christian Marois ◽  
René Doyon ◽  
Daniel Nadeau ◽  
René Racine ◽  
Martin Riopel ◽  
...  
Keyword(s):  
Imaging Camera ◽  
Substellar Companions ◽  
Differential Imaging

scholarly journals MIRACLES: atmospheric characterization of directly imaged planets and substellar companions at 4–5 μm

2020 ◽  
Vol 635 ◽  
pp. A182 ◽  
Author(s):  
T. Stolker ◽  
S. P. Quanz ◽  
K. O. Todorov ◽  
J. Kühn ◽  
P. Mollière ◽  
...  
Keyword(s):  
Careful Analysis ◽  
Surface Gravity ◽  
Blue Color ◽  
Very Large Telescope ◽  
Red Color ◽  
Flux Measurements ◽  
Low Mass ◽  
Substellar Companions ◽  
First Time

Context. Directly imaged planets and substellar companions are key targets for the characterization of self-luminous atmospheres. Their photometric appearance at 4–5 μm is sensitive to the chemical composition and cloud content of their atmosphere. Aims. We aim to systematically characterize the atmospheres of directly imaged low-mass companions at 4–5 μm. We want to homogeneously process the data, provide robust flux measurements, and compile a photometric library at thermal wavelengths of these mostly young, low-gravity objects. In this way, we want to find trends related to their spectral type and surface gravity by comparing with isolated brown dwarfs and predictions from atmospheric models. Methods. We used the high-resolution, high-contrast capabilities of NACO at the Very Large Telescope (VLT) to directly image the companions of HIP 65426, PZ Tel, and HD 206893 in the NB4.05 and/or M′ filters. For the same targets, and additionally β Pic, we also analyzed six archival VLT/NACO datasets which were taken with the NB3.74, L′, NB4.05, and M′ filters. The data processing and photometric extraction of the companions was done with PynPoint while the species toolkit was used to further analyze and interpret the fluxes and colors. Results. We detect for the first time HIP 65426 b, PZ Tel B, and HD 206893 B in the NB4.05 filter, PZ Tel B and HD 206893 B in the M′ filter, and β Pic b in the NB3.74 filter. We provide calibrated magnitudes and fluxes with a careful analysis of the error budget, both for the new and archival datasets. The L′–NB4.05 and L′–M′ colors of the studied sample are all red while the NB4.05–M′ color is blue for β Pic b, gray for PZ Tel B, and red for HIP 65426 b and HD 206893 B (although typically with low significance). The absolute NB4.05 and M′ fluxes of our sample are all larger than those of field dwarfs with similar spectral types. Finally, the surface gravity of β Pic b has been constrained to log g = 4.17−0.13+0.10 dex from its photometry and dynamical mass. Conclusions. A red color at 3–4 μm and a blue color at 4–5 μm might be (partially) caused by H2O and CO absorption, respectively, which are expected to be the most dominant gaseous opacities in hot (Teff ≳ 1300 K) atmospheres. The red characteristics of β Pic b, HIP 65426 b, and HD 206893 B at 3–5μm, as well as their higher fluxes in NB4.05 and M′ compared to field dwarfs, indicate that cloud densities are enhanced close to the photosphere as a result of their low surface gravity.

scholarly journals Visible Light Adaptive Optics Imaging of the Orion 218-354 Silhouette Disk

2013 ◽  
Vol 8 (S299) ◽  
pp. 159-160
Author(s):  
Katherine B. Follette ◽  
Laird M. Close ◽  
Jared R. Males ◽  
Derek Kopon ◽  
Ya-Lin Wu ◽  
...  
Keyword(s):  
High Resolution ◽  
Visible Light ◽  
Adaptive Optics ◽  
Central Star ◽  
Full Detail ◽  
Imaging Analysis ◽  
Large Telescope ◽  
Disk Structure ◽  
Adaptive Optics Imaging ◽  
Differential Imaging

AbstractWe present the first ground-based adaptive optics images of a silhouette disk. This disk, Orion 218-354, is seen in silhouette against the bright nebular background of Orion, and was resolved using the new Magellan Adaptive Secondary AO system and its VisAO camera in Simultaneous Differential Imaging (SDI) mode. PSF subtraction of Orion 218-354 reveals a disk ~1″ (400 AU) in radius, with the degree of absorption increasing steadily towards the center of the disk. By virtue of the central star being unsaturated, these data probe inward to a much smaller radius than previous HST images. Our data present a different picture than previous observers had hypothesized, namely that the disk is likely optically thin at Hα at least as far inward as ~20AU. In addition to being among the first high-resolution AO images taken in the optical on a large telescope, these data reveal the power of SDI imaging to illuminate disk structure, and speak to a bright future for visible AO imaging. Analysis of the results described briefly here can be found in full detail in Follette et al. (2013).

scholarly journals Combining high-contrast imaging and radial velocities to constrain the planetary architectures of nearby stars

2019 ◽  
Vol 630 ◽  
pp. A50 ◽  
Author(s):  
A. Boehle ◽  
S. P. Quanz ◽  
C. Lovis ◽  
D. Ségransan ◽  
S. Udry ◽  
...  
Keyword(s):  
Parameter Space ◽  
Major Axis ◽  
Solar Neighborhood ◽  
High Contrast ◽  
Contrast Imaging ◽  
Semi Major Axis ◽  
Detection Techniques ◽  
High Contrast Imaging ◽  
Nearby Stars ◽  
Substellar Companions

Context. Nearby stars are prime targets for exoplanet searches and characterization using a variety of detection techniques. Combining constraints from the complementary detection methods of high-contrast imaging (HCI) and radial velocity (RV) can further constrain the planetary architectures of these systems because these methods place limits at different regions of the companion mass and semi-major axis parameter space. Compiling a census of the planet population in the solar neighborhood is important to inform target lists for future space missions that will specifically target nearby stars to search for Earth analogs. Aims. We aim to constrain the planetary architectures from the combination of HCI and RV data for six nearby stars within 6 pc: τ Ceti, Kapteyn’s star, AX Mic, 40 Eri, HD 36395, and HD 42581. We explored where HCI adds information to constraints from the long-term RV monitoring data for these stars. Methods. We compiled the sample from stars with available archival VLT/NACO HCI data at L′ band (3.8 μm), where we expect substellar companions to be brighter for the typically older ages of nearby field stars (>1 Gyr). The NACO data were fully reanalyzed using the state-of-the-art direct imaging pipeline PynPoint and combined with RV data from HARPS, Keck/HIRES, and CORALIE. A Monte Carlo approach was used to assess the completeness in the companion mass and semi-major axis parameter space from the combination of the HCI and RV data sets. Results. We find that the HCI data add significant information to the RV constraints, increasing the completeness for certain companions masses and semi-major axes by up to 68–99% for four of the six stars in our sample, and by up to 1–13% for the remaining stars. The improvements are strongest for intermediate semi-major axes (15–40 AU), corresponding to the semi-major axes of the ice giants in our own solar system. The HCI mass limits reach 5–20 MJup in the background-limited regime, depending on the age of the star. Conclusions. Through the combination of HCI and RV data, we find that stringent constraints can be placed on the possible substellar companions in these systems. Applying these methods systematically to nearby stars will quantify our current knowledge of the planet population in the solar neighborhood and inform future observations.

scholarly journals SPHERE view of Wolf-Rayet 104

2018 ◽  
Vol 618 ◽  
pp. A108 ◽  
Author(s):  
A. Soulain ◽  
F. Millour ◽  
B. Lopez ◽  
A. Matter ◽  
E. Lagadec ◽  
...  
Keyword(s):  
Physical Properties ◽  
Angular Resolution ◽  
Spatial Scales ◽  
Binary Star ◽  
Central Star ◽  
Opening Angle ◽  
High Angular Resolution ◽  
Spiral Coil ◽  
Very Large Telescope ◽  
First Time

Context. WR104 is an emblematic dusty Wolf-Rayet star and the prototypical member of a sub-group hosting spirals that are mainly observable with high-angular resolution techniques. Previous aperture masking observations showed that WR104 is likely to be an interacting binary star at the end of its life. However, several aspects of the system are still unknown. This includes the opening angle of the spiral, the dust formation locus, and the link between the central binary star and a candidate companion star detected with the Hubble Space Telescope (HST) at 1′′. Aims. Our aim was to directly image the dusty spiral or “pinwheel” structure around WR104 for the first time and determine its physical properties at large spatial scales. We also wanted to address the characteristics of the candidate companion detected by the HST. Methods. For this purpose, we used SPHERE and VISIR at the Very Large Telescope to image the system in the near- and mid-infrared, respectively. Both instruments furnished an excellent view of the system at the highest angular resolution a single, ground-based telescope can provide. Based on these direct images, we then used analytical and radiative transfer models to determine several physical properties of the system. Results. Employing a different technique than previously used, our new images have allowed us to confirm the presence of the dust pinwheel around the central star. We have also detected up to five revolutions of the spiral pattern of WR104 in the K band for the first time. The circumstellar dust extends up to 2 arcsec from the central binary star in the N band, corresponding to the past 20 yr of mass loss. Moreover, we found no clear evidence of a shadow of the first spiral coil onto the subsequent ones, which likely points to a dusty environment less massive than inferred in previous studies. We have also confirmed that the stellar candidate companion previously detected by the HST is gravitationally bound to WR104 and herein provide information about its nature and orbital elements.

Early results from ChanPLaNS: Mystery of hard X-ray emitting CSPNe

2011 ◽  
Vol 7 (S283) ◽  
pp. 450-451
Author(s):  
Rodolfo Montez ◽  
J. H. Kastner ◽  
B. Balick ◽  
E. Behar ◽  
E. Blackman ◽  
...  
Keyword(s):  
White Dwarf ◽  
Binary Star ◽  
Central Star ◽  
Point Sources ◽  
Solar Neighborhood ◽  
High Excitation ◽  
High Detection Rate ◽  
X Ray ◽  
Early Results ◽  
Red Giant

AbstractWe are presently using the Chandra X-ray Observatory to conduct the first systematic X-ray survey of planetary nebulae (PNe) in the solar neighborhood. The Chandra Planetary Nebula Survey (ChanPlaNS) is a 570 ks Chandra Cycle 12 Large Program targeting 21 high-excitation PNe within ~1.5 kpc of Earth. When complete, this survey will provide a suite of new X-ray diagnostics that will inform the study of late stellar evolution, binary star astrophysics, and wind interactions. Among the early results of ChanPlaNS (when combined with archival Chandra data) is a surprisingly high detection rate of relatively hard X-ray emission from CSPNe. Specifically, X-ray point sources are clearly detected in roughly half of the ~30 high-excitation PNe observed thus far by Chandra, and all but one of these X-ray-emitting CSPNe display evidence for a hard (few MK) component in their Chandra spectra. Only the central star of the Dumbbell appears to display “pure” hot blackbody emission from a ~200 kK hot white dwarf photosphere in the X-ray band. Potential explanations for the“excess” hard X-ray emission detected from the other CSPNe include late-type companions (heretofore undetected, in most cases) whose coronae have been rejuvenated by recent interactions with the mass-losing WD progenitor, non-LTE effects in hot white dwarf photospheres, self-shocking variable winds from the central star, and slow (re-)accretion of previously ejected red giant envelope mass.

scholarly journals Detection of Hα emission from PZ Telescopii B using SPHERE/ZIMPOL

2019 ◽  
Vol 631 ◽  
pp. A84 ◽  
Author(s):  
Arianna Musso Barcucci ◽  
Gabriele Cugno ◽  
Ralf Launhardt ◽  
André Müller ◽  
Judit Szulagyi ◽  
...  
Keyword(s):  
Activity Levels ◽  
Bolometric Luminosity ◽  
Chromospheric Activity ◽  
Very Large Telescope ◽  
Hα Emission ◽  
Average Activity ◽  
Formation And Evolution ◽  
Photometric Measurements ◽  
Differential Imaging ◽  
M Dwarf

Hα is a powerful tracer of accretion and chromospheric activity, which has been detected in the case of young brown dwarfs and even recently in planetary mass companions (e.g. PDS70 b and c). Hα detections and characterisation of brown dwarf and planet companions can further our knowledge of their formation and evolution, and expanding such a sample is therefore our primary goal. We used the Zurich Imaging POLarimeter (ZIMPOL) of the SPHERE instrument at the Very Large Telescope (VLT) to observe the known 38−72 MJ companion orbiting PZ Tel, obtaining simultaneous angular differential imaging observations in both continuum and narrow Hα band. We detect Hα emission from the companion, making this only the second Hα detection of a companion using the SPHERE instrument. We used our newly added astrometric measurements to update the orbital analysis of PZ Tel B, and we used our photometric measurements to evaluate the Hα line flux. Given the estimated bolometric luminosity, we obtained an Hα activity (log(LHα/Lbol)) between −4.16 and −4.31. The Hα activity of PZ Tel B is consistent with known average activity levels for M dwarf of the same spectral type. Given the absence of a known gaseous disk and the relatively old age of the system (24 Myr), we conclude that the Hα emission around PZ Tel B is likely due to chromospheric activity.

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