scholarly journals GG Tauri A: dark shadows on the ringworld

2019 ◽  
Vol 628 ◽  
pp. A88 ◽  
Author(s):  
R. Brauer ◽  
E. Pantin ◽  
E. Di Folco ◽  
E. Habart ◽  
A. Dutrey ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Near Infrared ◽  
Binary Star ◽  
Scattered Light ◽  
Circumstellar Disks ◽  
Infrared Emission ◽  
Close Binary ◽  
Spectral Energy ◽  
Multiple Star ◽  
The Individual

Context. With its high complexity, large size, and close distance, the ringworld around GG Tau A is an appealing case to study the formation and evolution of protoplanetary disks around multiple star systems. However, investigations with radiative transfer models usually neglect the influence of the circumstellar dust around the individual stars. Aims. We investigate how circumstellar disks around the stars of GG Tau A influence the emission that is scattered at the circumbinary disk and if constraints on these circumstellar disks can be derived. Methods. We performed radiative transfer simulations with the POLArized RadIation Simulator (POLARIS) to obtain spectral energy distributions and emission maps in the H-Band (near-infrared). Subsequently, we compared them with observations to achieve our aims. Results. We studied the ratio of polarized intensity at different locations in the circumbinary disk. We conclude that the observed scattered-light near-infrared emission is best reproduced if the circumbinary disk lies in the shadow of at least two coplanar circumstellar disks surrounding the central stars. This implies that the inner wall of the circumbinary disk is strongly obscured around the midplane, while the observed emission is actually dominated by the upper-most disk layers. In addition, the inclined dark lane (“gap”) on the western side of the circumbinary disk, which has been a stable, nonrotating, feature for approximately 20 yr, can only be explained by the self-shadowing of a misaligned circumstellar disk surrounding one of the two components of the secondary close-binary star GG Tau Ab.

scholarly journals Optical and UV surface brightness of translucent dark nebulae

2018 ◽  
Vol 617 ◽  
pp. A42 ◽  
Author(s):  
K. Mattila ◽  
M. Haas ◽  
L. K. Haikala ◽  
Y-S. Jo ◽  
K. Lehtinen ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Near Infrared ◽  
Scattered Light ◽  
Spectral Energy Distribution ◽  
Fluorescence Emission ◽  
Infrared Emission ◽  
Line Of Sight ◽  
Spectral Energy ◽  
Optical Extinction ◽  
Fluorescent Emission

Context. Dark nebulae display a surface brightness because dust grains scatter light of the general interstellar radiation field (ISRF). High-galactic-latitudes dark nebulae are seen as bright nebulae when surrounded by transparent areas which have less scattered light from the general galactic dust layer. Aims. Photometry of the bright dark nebulae LDN 1780, LDN 1642, and LBN 406 shall be used to derive scattering properties of dust and to investigate the presence of UV fluorescence emission by molecular hydrogen and the extended red emission (ERE). Methods. We used multi-wavelength optical photometry and imaging at ground-based telescopes and archival imaging and spectroscopic UV data from the spaceborn GALEX and SPEAR/FIMS instruments. In the analysis we used Monte Carlo RT and both observational data and synthetic models for the ISRF in the solar neighbourhood. The line-of-sight extinctions through the clouds have been determined using near infrared excesses of background stars and the 200/250 μm far infrared emission by dust as measured using the ISO and Herschel space observatories. Results. The optical surface brightness of the three target clouds can be explained in terms of scattered light. The dust albedo ranges from ~0.58 at 3500 Å to ~0.72 at 7500 Å. The spectral energy distribution of LDN 1780 is explained in terms of optical depth and background scattered light effects instead of the original published suggestion in terms of ERE. The far-ultraviolet surface brightness of LDN 1780 cannot be explained by scattered light only. In LDN 1780, H2 fluorescent emission in the wavelength range 1400–1700 Å has been detected and analysed. Conclusions. Our albedo values are in good agreement with the predictions of the dust model of Weingartner and Draine and with the THEMIS CMM model for evolved core-mantle grains. The distribution of H2 fluorescent emission in LDN 1780 shows a pronounced dichotomy with a strong preference for its southern side where enhanced illumination is impinging from the Sco OB2 association and the O star ζ Oph. A good correlation is found between the H2 fluorescence and a previously mapped 21-cm excess emission. The H2 fluorescence emission in LDN 1780 has been modelled using a PDR code; the resulting values for H2 column density and the total gas density are consistent with the estimates derived from CO observations and optical extinction along the line of sight.

scholarly journals Investigating the young solar system analog HD 95086

2018 ◽  
Vol 617 ◽  
pp. A76 ◽  
Author(s):  
G. Chauvin ◽  
R. Gratton ◽  
M. Bonnefoy ◽  
A.-M. Lagrange ◽  
J. de Boer ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Near Infrared ◽  
Scattered Light ◽  
Spectral Energy Distribution ◽  
Giant Planet ◽  
Giant Planets ◽  
Dual Band ◽  
Spectral Energy ◽  
Semi Major Axis ◽  
Integral Field Spectrograph

Context. HD 95086 (A8V, 17 Myr) hosts a rare planetary system for which a multi-belt debris disk and a giant planet of 4–5 MJup have been directly imaged. Aims. Our study aims to characterize the global architecture of this young system using the combination of radial velocity and direct imaging observations. We want to characterize the physical and orbital properties of HD 95086 b, search for additional planets at short and wide orbits and image the cold outer debris belt in scattered light. Methods. We used HARPS at the ESO 3.6 m telescope to monitor the radial velocity of HD 95086 over two years and investigate the existence of giant planets at less than 3 au orbital distance. With the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE at VLT, we imaged the faint circumstellar environment beyond 10 au at six epochs between 2015 and 2017. Results. We do not detect additional giant planets around HD 95086. We identify the nature (bound companion or background contaminant) of all point-like sources detected in the IRDIS field of view. None of them correspond to the ones recently discovered near the edge of the cold outer belt by ALMA. HD 95086 b is resolved for the first time in J-band with IFS. Its near-infrared spectral energy distribution is well fitted by a few dusty and/or young L7–L9 dwarf spectral templates. The extremely red 1–4 μm spectral distribution is typical of low-gravity objects at the L/T spectral type transition. The planet’s orbital motion is resolved between January 2015 and May 2017. Together with past NaCo measurements properly re-calibrated, our orbital fitting solutions favor a retrograde low to moderate-eccentricity orbit e = 0.2+0.3−0.2, with a semi-major axis ~52 au corresponding to orbital periods of ~288 yr and an inclination that peaks at i = 141°, which is compatible with a planet-disk coplanar configuration. Finally, we report the detection in polarimetric differential imaging of the cold outer debris belt between 100 and 300 au, consistent in radial extent with recent ALMA 1.3 mm resolved observations.

scholarly journals Flybys in protoplanetary discs – II. Observational signatures

2019 ◽  
Vol 491 (1) ◽  
pp. 504-514 ◽  
Author(s):  
Nicolás Cuello ◽  
Fabien Louvet ◽  
Daniel Mentiplay ◽  
Christophe Pinte ◽  
Daniel J Price ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Near Infrared ◽  
Scattered Light ◽  
Line Emission ◽  
Star Clusters ◽  
Post Process ◽  
Accretion Rates ◽  
Fu Ori ◽  
Hydrodynamical Simulations ◽  
Multiwavelength Observations

ABSTRACT Tidal encounters in star clusters perturb discs around young protostars. In Cuello et al., we detailed the dynamical signatures of a stellar flyby in both gas and dust. Flybys produce warped discs, spirals with evolving pitch angles, increasing accretion rates, and disc truncation. Here, we present the corresponding observational signatures of these features in optical/near-infrared scattered light and (sub) millimetre continuum and CO line emission. Using representative prograde and retrograde encounters for direct comparison, we post-process hydrodynamical simulations with radiative transfer methods to generate a catalogue of multiwavelength observations. This provides a reference to identify flybys in recent near-infrared and submillimetre observations (e.g. RW Aur, AS 205, HV Tau and DO Tau, FU Ori, V2775 Ori, and Z CMa).

scholarly journals Infrared spectroscopy of the merger candidate KIC 9832227

2018 ◽  
Vol 615 ◽  
pp. A120 ◽  
Author(s):  
Ya. V. Pavlenko ◽  
A. Evans ◽  
D. P. K. Banerjee ◽  
J. Southworth ◽  
M. Shahbandeh ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared ◽  
Binary Star ◽  
Circumstellar Envelope ◽  
Stellar Rotation ◽  
Coronal Activity ◽  
Orbital Phase ◽  
Solar Metallicity ◽  
Contact Binary ◽  
The Individual

Context. It has been predicted that the object KIC 9832227 – a contact binary star – will undergo a merger in 2022.2 ± 0.7. We describe the near-infrared (NIR) spectrum of this object as an impetus to obtain pre-merger data. Aims. We aim to characterise (i) the nature of the individual components of the binary and (ii) the likely circumbinary environment, so that the merger – if and when it occurs – can be interpreted in an informed manner. Methods. We use infrared (IR) spectroscopy in the wavelength range 0.7–2.5 μm, to which we fit model atmospheres to represent the individual stars. We use the binary ephemeris to determine the orbital phase at the time of observation. Results. We find that the IR spectrum is best fitted by a single component with effective temperature 5920 K, log[g] = 4.1, and solar metallicity, consistent with the fact that the system was observed at conjunction. Conclusions. The strength of the IR H lines is consistent with a high value of logg, and the strength of the Ca II triplet indicates the presence of a chromosphere, as might be expected from rapid stellar rotation. The He I absorption we observe likely arises in He excited by coronal activity in a circumstellar envelope, suggesting that the weakness of the Ca II triplet is also likely chromospheric in origin.

scholarly journals The single-sided pulsator CO Camelopardalis

2020 ◽  
Vol 494 (4) ◽  
pp. 5118-5133 ◽  
Author(s):  
D W Kurtz ◽  
G Handler ◽  
S A Rappaport ◽  
H Saio ◽  
J Fuller ◽  
...  
Keyword(s):  
Binary Stars ◽  
Binary Star ◽  
Spectral Energy Distribution ◽  
Radial Velocities ◽  
Close Binary ◽  
Theoretical Modelling ◽  
Spectral Energy ◽  
Primary Star ◽  
Pulsating Stars ◽  
Secondary Star

ABSTRACT CO Cam (TIC 160268882) is the second ‘single-sided pulsator’ to be discovered. These are stars where one hemisphere pulsates with a significantly higher amplitude than the other side of the star. CO Cam is a binary star comprised of an Am δ Sct primary star with Teff = 7070 ± 150 K, and a spectroscopically undetected G main-sequence secondary star. The dominant pulsating side of the primary star is centred on the L1 point. We have modelled the spectral energy distribution combined with radial velocities, and independently the TESS light curve combined with radial velocities. Both of these give excellent agreement and robust system parameters for both stars. The δ Sct star is an oblique pulsator with at least four low radial overtone (probably) f modes with the pulsation axis coinciding with the tidal axis of the star, the line of apsides. Preliminary theoretical modelling indicates that the modes must produce much larger flux perturbations near the L1 point, although this is difficult to understand because the pulsating star does not come near to filling its Roche lobe. More detailed models of distorted pulsating stars should be developed. These newly discovered single-sided pulsators offer new opportunities for astrophysical inference from stars that are oblique pulsators in close binary stars.

scholarly journals Surveying the Giant H ii Regions of the Milky Way with SOFIA. III. W49A

2021 ◽  
Vol 923 (2) ◽  
pp. 198
Author(s):  
James M. De Buizer ◽  
Wanggi Lim ◽  
Mengyao Liu ◽  
Nicole Karnath ◽  
James T. Radomski
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Infrared Imaging ◽  
Physical Nature ◽  
Infrared Emission ◽  
Spectral Energy ◽  
H Ii Regions ◽  
Extended Radio ◽  
The Galaxy ◽  
Western Side

Abstract We present our third set of results from our mid-infrared imaging survey of Milky Way Giant H ii regions with our detailed analysis of W49A, one of the most distant, yet most luminous, GH ii regions in the Galaxy. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) to obtain 20 and 37 μm images of the entire ∼5.′0 × 3.′5 infrared-emitting area of W49A at a spatial resolution of ∼3″. Utilizing these SOFIA data in conjunction with previous multiwavelength observations from the near-infrared to radio, including Spitzer-IRAC and Herschel-PACS archival data, we investigate the physical nature of individual infrared sources and subcomponents within W49A. For individual compact sources, we used the multiwavelength photometry data to construct spectral energy distributions (SEDs) and fit them with massive young stellar object (MYSO) SED models and find 22 sources that are likely to be MYSOs. Ten new sources are identified for the first time in this work. Even at 37 μm we are unable to detect infrared emission from the sources on the western side of the extremely extinguished ring of compact radio emission sources known as the Welch Ring. Utilizing multiwavelength data, we derived luminosity-to-mass ratio and virial parameters of the extended radio subregions of W49A to estimate their relative ages and find that overall the subcomponents of W49A have a very small spread in evolutionary state compared to our previously studied GH ii regions.

scholarly journals Disks Around T Tauri Stars with SPHERE (DARTTS-S)

2020 ◽  
Vol 633 ◽  
pp. A82 ◽  
Author(s):  
A. Garufi ◽  
H. Avenhaus ◽  
S. Pérez ◽  
S. P. Quanz ◽  
R. G. van Holstein ◽  
...  
Keyword(s):  
Scattered Light ◽  
Spectral Energy Distribution ◽  
Surrounding Medium ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Spectral Energy ◽  
Near Ir ◽  
Nir Imaging ◽  
T Tauri ◽  
Disk Size

Context. Near-IR polarimetric images of protoplanetary disks enable us to characterize substructures that might be due to the interaction with (forming) planets. The available census is strongly biased toward massive disks around old stars, however. Aims. The DARTTS program aims at alleviating this bias by imaging a large number of T Tauri stars with diverse properties. Methods. DARTTS-S employs VLT/SPHERE to image the polarized scattered light from disks. In parallel, DARTTS-A provides ALMA images of the same targets for a comparison of different dust components. In this work, we present new SPHERE images of 21 circumstellar disks, which is the largest sample released to date. We also recalculated some relevant stellar and disk properties following Gaia DR2. Results. The targets of this work are significantly younger than those published thus far with polarimetric near-IR (NIR) imaging. Scattered light is unambiguously resolved in 11 targets, and some polarized unresolved signal is detected in 3 additional sources. Some disk substructures are detected. However, the paucity of spirals and shadows from this sample reinforces the trend according to which these NIR features are associated with Herbig stars, either because they are older or more massive. Furthermore, disk rings that are apparent in ALMA observations of some targets do not appear to have corresponding detections with SPHERE. Inner cavities larger than ~15 au are also absent from our images, even though they are expected from the spectral energy distribution. On the other hand, 3 objects show extended filaments at larger scale that are indicative of strong interaction with the surrounding medium. All but one of the undetected disks are best explained by their limited size (≲20 au), and the high occurrence of stellar companions in these sources suggests an important role in limiting the disk size. One undetected disk is massive and very large at millimeter wavelengths, implying that it is self-shadowed in the NIR. Conclusions. This work paves the way toward a more complete and less biased sample of scattered-light observations, which is required to interpret how disk features evolve throughout the disk lifetime.

scholarly journals Spatial segregation of dust grains in transition disks

2019 ◽  
Vol 624 ◽  
pp. A7 ◽  
Author(s):  
M. Villenave ◽  
M. Benisty ◽  
W. R. F. Dent ◽  
F. Ménard ◽  
A. Garufi ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Near Infrared ◽  
Scattered Light ◽  
Radiative Transfer Model ◽  
Occurrence Rate ◽  
Transfer Model ◽  
Star Forming ◽  
Spatially Resolved ◽  
Wide Range ◽  
Transition Disks

Context. The mechanisms governing the opening of cavities in transition disks are not fully understood. Several processes have been proposed, but their occurrence rate is still unknown. Aims. We present spatially resolved observations of two transition disks, and aim at constraining their vertical and radial structure using multiwavelength observations that probe different regions of the disks and can help understanding the origin of the cavities. Methods. We have obtained near-infrared scattered light observations with VLT/SPHERE of the transition disks 2MASS J16083070-3828268 (J1608) and RXJ1852.3-3700 (J1852), located in the Lupus and Corona Australis star-forming regions respectively. We complement our datasets with archival ALMA observations, and with unresolved photometric observations covering a wide range of wavelengths. We performed radiative transfer modeling to analyze the morphology of the disks, and then compare the results with a sample of 20 other transition disks observed with both SPHERE and ALMA. Results. We detect scattered light in J1608 and J1852 up to a radius of 0.54′′ and 0.4′′ respectively. The image of J1608 reveals a very inclined disk (i ~ 74°), with two bright lobes and a large cavity. We also marginally detect the scattering surface from the rear-facing side of the disk. J1852 shows an inner ring extending beyond the coronagraphic radius up to 15 au, a gap and a second ring at 42 au. Our radiative transfer model of J1608 indicates that the millimeter-sized grains are less extended vertically and radially than the micron-sized grains, indicating advanced settling and radial drift. We find good agreement with the observations of J1852 with a similar model, but due to the low inclination of the system, the model remains partly degenerate. The analysis of 22 transition disks shows that, in general, the cavities observed in scattered light are smaller than the ones detected at millimeter wavelengths. Conclusions. The analysis of a sample of transition disks indicates that the small grains, well coupled to the gas, can flow inward of the region where millimeter grains are trapped. While 15 out of the 22 cavities in our sample could be explained by a planet of less than 13 Jupiter masses, the others either require the presence of a more massive companion or of several low-mass planets.

Direct Imaging of Circumstellar Disks in the Orion Nebula

1997 ◽  
Vol 163 ◽  
pp. 546-548
Author(s):  
Mark J. McCaughrean
Keyword(s):  
Near Infrared ◽  
Hubble Space Telescope ◽  
Circumstellar Disks ◽  
Infrared Emission ◽  
Orion Nebula ◽  
Direct Imaging ◽  
Stellar Photometry ◽  
Inclination Angles ◽  
Low Mass ◽  
Lower Limits

AbstractWe present observations of the Orion Nebula made with the Hubble Space Telescope in which a number of stars are seen surrounded by dark silhouettes seen projected against the bright background HII region. We find a variety of morphologies, all consistent with thin circumstellar disks spanning a range of diameters (50 to 1000 AU) and inclination angles (0 to > 80 degrees). The silhouette intensity profiles cannot be fit by standard disk models in which the surface density follows a radial power law with an exponent in the range −0.75 to −1.5. Rather, the data are best fit by opaque inner disks with exponential edges, and we discuss possible physical origins of this apparent truncation. Masses in the range 6 × l026−4 × 1030 g (i.e., up to 0.002 M⊙) are determined for the disks by assuming that the faint light measured from them is background light transmitted through the disk. However, these are strict lower limits on the true disk masses, as most of this light can be accounted for by PSF blurring and scattering in the HST optical train; the present observations are in fact consistent with completely opaque disks. Central stars are seen directly in five of the silhouettes, while the presence of a star is inferred in the sixth, where small reflection nebulae are seen above and below the plane of the near edge-on disk. Optical and near-infrared stellar photometry is consistent with young (~ 1 Myr) low-mass (0.3−1.5 M⊙) stars, with several showing evidence for excess near-infrared emission from the disk inner edge. These direct imaging observations are discussed in the wider context of circumstellar disks in the Orion Nebula and Trapezium Cluster, additionally revealed as compact ionized nebulae (so-called “proplyds”) in the vicinity of the central OB stars, and via infrared (>2µm) excesses in stellar photometry. Overall, disks are found to be common in the cluster (>50% of all stars), implying that they can survive the rigours of life near massive stars.

scholarly journals Physical Parameters of the Visually Close Binary Systems Hip70973 and Hip72479

2012 ◽  
Vol 29 (4) ◽  
pp. 523-528 ◽  
Author(s):  
M. Al-Wardat
Keyword(s):  
Binary Systems ◽  
Spectral Energy Distribution ◽  
Close Binary ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Spectral Energy Distributions ◽  
Combined System ◽  
Energy Distributions ◽  
Close Binary Systems ◽  
The Individual

AbstractAtmospheric modelling of the components of the visually close binary systems Hip70973 and Hip72479 was used to estimate the individual physical parameters of their components. The model atmospheres were constructed using a grid of Kurucz solar metalicity blanketed models and used to compute a synthetic spectral energy distribution for each component separately, and hence for the combined system. The total observational spectral energy distributions of the systems were used as a reference for comparison with the synthetic ones. We used the feedback modified parameters and iteration method to obtain the best fit between synthetic and observational spectral energy distributions. The physical parameters of the components of the system Hip70973 were derived as = 5700 ± 75 K, = 5400 ± 75 K, log ga = 4.50 ± 0.05, log gb = 4.50 ± 0.05, Ra = 0.98 ± 0.07 R⊙, Rb = 0.89 ± 0.07 R⊙, and π = 26.25 ± 1.95 mas, with G4 and G9 spectral types, and those of the system Hip72479 as = 5400 ± 50 K, = 5180 ± 50 K, log ga = 4.50 ± 0.05, log gb = 4.60 ± 0.05, Ra = 0.89 ± 0.07 R⊙, Rb = 0.80 ± 0.07 R⊙, and π = 23.59 ± 1.00 mas, with G9 and K1 spectral types.

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