High‐Resolution Submillimeter Constraints on Circumstellar Disk Structure

AbstractHigh-resolution Coude observations of non-axisymmetric line emission -from the dwarf nova SS Cygni are presented. By subtracting the constant line component, the asymmetric line emission responsible for the observed phase shift between the absorption and emission line radial velocity curves can be isolated. The extra emission is a large fraction of the total line emission and extends to large velocities (~1500 km sec−1). The phase stability of the emission demands a large-scale structure which is fixed in the frame of the binary. A magnetic origin of the excitation cannot De ruled out but is implausible. A simple explanation is that the accretion stream from the companion star is able to spill over the sags of the disk, introducing emission at non-circular velocities and most likely disturbing the upper layers of the accretion disk.

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Visible and near-infrared spectro-interferometric analysis of the edge-on Be star o Aquarii

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936039 ◽

2020 ◽

Vol 636 ◽

pp. A110 ◽

Cited By ~ 1

Author(s):

E. S. G. de Almeida ◽

A. Meilland ◽

A. Domiciano de Souza ◽

P. Stee ◽

D. Mourard ◽

...

Keyword(s):

Steady State ◽

Near Infrared ◽

Spectral Energy Distribution ◽

Kinematic Model ◽

Spectral Energy ◽

Circumstellar Disk ◽

Be Stars ◽

Rotational Rate ◽

Disk Structure ◽

Be Star

Aims. We present a detailed visible and near-infrared spectro-interferometric analysis of the Be-shell star o Aquarii from quasi-contemporaneous CHARA/VEGA and VLTI/AMBER observations. Methods. We analyzed spectro-interferometric data in the Hα (VEGA) and Brγ (AMBER) lines using models of increasing complexity: simple geometric models, kinematic models, and radiative transfer models computed with the 3D non-LTE code HDUST. Results. We measured the stellar radius of o Aquarii in the visible with a precision of 8%: 4.0 ± 0.3 R⊙. We constrained the circumstellar disk geometry and kinematics using a kinematic model and a MCMC fitting procedure. The emitting disk sizes in the Hα and Brγ lines were found to be similar, at ~10–12 stellar diameters, which is uncommon since most results for Be stars indicate a larger extension in Hα than in Brγ. We found that the inclination angle i derived from Hα is significantly lower (~15°) than the one derived from Brγ: i ~ 61.2° and 75.9°, respectively. While the two lines originate from a similar region of the disk, the disk kinematics were found to be near to the Keplerian rotation (i.e., β = −0.5) in Brγ (β ~ −0.43), but not in Hα (β ~ −0.30). After analyzing all our data using a grid of HDUST models (BeAtlas), we found a common physical description for the circumstellar disk in both lines: a base disk surface density Σ0 = 0.12 g cm−2 and a radial density law exponent m = 3.0. The same kind of discrepancy, as with the kinematic model, is found in the determination of i using the BeAtlas grid. The stellar rotational rate was found to be very close (~96%) to the critical value. Despite being derived purely from the fit to interferometric data, our best-fit HDUST model provides a very reasonable match to non-interferometric observables of o Aquarii: the observed spectral energy distribution, Hα and Brγ line profiles, and polarimetric quantities. Finally, our analysis of multi-epoch Hα profiles and imaging polarimetry indicates that the disk structure has been (globally) stable for at least 20 yr. Conclusions. Looking at the visible continuum and Brγ emission line only, o Aquarii fits in the global scheme of Be stars and their circumstellar disk: a (nearly) Keplerian rotating disk well described by the viscous decretion disk (VDD) model. However, the data in the Hα line shows a substantially different picture that cannot fully be understood using the current generation of physical models of Be star disks. The Be star o Aquarii presents a stable disk (close to the steady-state), but, as in previous analyses, the measured m is lower than the standard value in the VDD model for the steady-state regime (m = 3.5). This suggests that some assumptions of this model should be reconsidered. Also, such long-term disk stability could be understood in terms of the high rotational rate that we measured for this star, the rate being a main source for the mass injection in the disk. Our results on the stellar rotation and disk stability are consistent with results in the literature showing that late-type Be stars are more likely to be fast rotators and have stable disks.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313008193 ◽

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).

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High-Resolution Near-Infrared Polarimetry of a Circumstellar Disk around UX Tau A

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/64.6.124 ◽

2012 ◽

Vol 64 (6) ◽

pp. 124 ◽

Cited By ~ 28

Author(s):

Ryoko Tanii ◽

Yoichi Itoh ◽

Tomoyuki Kudo ◽

Tomonori Hioki ◽

Yumiko Oasa ◽

...

Keyword(s):

High Resolution ◽

Near Infrared ◽

Circumstellar Disk

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Coronagraphic imaging of the Beta Pictoris circumstellar disk - Evidence of changing disk structure within 100 AU

The Astrophysical Journal ◽

10.1086/186907 ◽

1993 ◽

Vol 411 ◽

pp. L41 ◽

Cited By ~ 35

Author(s):

David A. Golimowski ◽

Samuel T. Durrance ◽

Mark Clampin

Keyword(s):

Circumstellar Disk ◽

Disk Structure ◽

Beta Pictoris

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High‐Resolution Near‐Infrared Images and Models of the Circumstellar Disk in HH 30

The Astrophysical Journal ◽

10.1086/321627 ◽

2001 ◽

Vol 556 (2) ◽

pp. 958-969 ◽

Cited By ~ 80

Author(s):

Angela S. Cotera ◽

Barbara A. Whitney ◽

Erick Young ◽

Michael J. Wolff ◽

Kenneth Wood ◽

...

Keyword(s):

High Resolution ◽

Near Infrared ◽

Circumstellar Disk ◽

Infrared Images

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High‐Resolution Near‐Infrared Observations of the Circumstellar Disk System in the Bok Globule CB 26

The Astrophysical Journal ◽

10.1086/425291 ◽

2004 ◽

Vol 617 (1) ◽

pp. 418-424 ◽

Cited By ~ 16

Author(s):

B. Stecklum ◽

R. Launhardt ◽

O. Fischer ◽

A. Henden ◽

Ch. Leinert ◽

...

Keyword(s):

High Resolution ◽

Near Infrared ◽

Circumstellar Disk ◽

Disk System ◽

Infrared Observations

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Discovery of a stellar companion to HD 131399A

Astronomy and Astrophysics ◽

10.1051/0004-6361/201730978 ◽

2017 ◽

Vol 608 ◽

pp. L9 ◽

Cited By ~ 1

Author(s):

A.-M. Lagrange ◽

M. Keppler ◽

H. Beust ◽

L. Rodet ◽

N. Meunier ◽

...

Keyword(s):

High Resolution ◽

Binary System ◽

Planet Formation ◽

Giant Planet ◽

Dynamical Evolution ◽

Young Stars ◽

Circumstellar Disk ◽

Mass Star ◽

Low Mass

Context. The giant exoplanets imaged on wide orbits (≥10 au) around young stars challenge the classical theories of planet formation. The presence of perturbing bodies could have played a role in the dynamical evolution of the planets once formed. Aims. We aim to search for close companions to HD 131399, a star around which a giant planet has been discovered, at a projected separation of about 80 au. The star also appears to be a member of a wide (320 au) binary system. Methods. We recorded HARPS high resolution spectra in January 2017. Results. We find that HD 131399A is probably seen close to pole-on. We discover a low mass star companion that orbits with a period of about 10 days on a misaligned orbit. Even though the companion does not have an impact on the current dynamical evolution of the planet, it could have played a role in its setting and in clearing the circumstellar disk from which the planet may originate.

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High-resolution spectroscopy of giant stars in the open clusters IC 4651 and IC 4725

Canadian Journal of Physics ◽

10.1139/cjp-2016-0912 ◽

2017 ◽

Vol 95 (9) ◽

pp. 862-868 ◽

Cited By ~ 1

Author(s):

Orlando J. Katime Santrich ◽

Silvia Rossi

Keyword(s):

High Resolution ◽

Solar Spectrum ◽

Open Clusters ◽

High Resolution Spectroscopy ◽

Local Thermal Equilibrium ◽

Atmospheric Parameters ◽

Chemical Abundances ◽

Abundance Pattern ◽

Giant Stars ◽

Disk Structure

Open clusters are important astrophysical laboratories to study the stellar formation and evolution and to verify the disk structure of the Milky Way. We present calculations of stellar atmospheric parameters and s-process abundances for nine giant stars in the galactic open clusters IC 4651 and IC 4725. These objects have their memberships confirmed from dynamic studies and chemical analysis. The high-resolution spectra are available in the FEROS ESO archive. We have applied a line by line analysis relative to Juno solar spectrum to determine the stellar atmospheric parameters and chemical abundances of Y II, Zr I, La II, Ce II, and Nd II under the local thermal equilibrium hypothesis. The obtained results were compared to the literature values. The derived s-process abundance pattern agrees with the most recent behaviors reported for giant stars in galactic open clusters.

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