Possibility to locate the position of the H2O snowline in protoplanetary disks through spectroscopic observations

2017 ◽  
Vol 13 (S332) ◽  
pp. 113-120
Author(s):  
Shota Notsu ◽  
Hideko Nomura ◽  
Catherine Walsh ◽  
Mitsuhiko Honda ◽  
Tomoya Hirota ◽  
...  
Keyword(s):  
Protoplanetary Disks ◽  
Central Star ◽  
Velocity Profiles ◽  
Emission Lines ◽  
High Dispersion ◽  
Line Profiles ◽  
Mid Infrared ◽  
Spectroscopic Observations ◽  
T Tauri ◽  
Hot Surface

AbstractObservationally measuring the location of the H2O snowline is crucial for understanding the planetesimal and planet formation processes, and the origin of water on Earth. The velocity profiles of emission lines from protoplanetary disks are usually affected by Doppler shift due to Keplerian rotation and thermal broadening. Therefore, the velocity profiles are sensitive to the radial distribution of the line-emitting regions. In our work (Notsu et al. 2016, 2017), we found candidate water lines to locate the position of the H2O snowline through future high-dispersion spectroscopic observations. First, we calculated the chemical composition of the disks around a T Tauri star and a Herbig Ae star using chemical kinetics. We confirmed that the abundance of H2O gas is high not only in the hot midplane region inside the H2O snowline but also in the hot surface layer and the photodesorption region of the outer disk. The position of the H2O snowline in the Herbig Ae disk exists at a larger radius from the central star than that in the T Tauri disk. Second, we calculated the H2O line profiles and identified that H2O emission lines with small Einstein A coefficients (∼10−6 − 10−3 s−1) and relatively high upper state energies (∼ 1000K) are dominated by emission from the hot midplane region inside the H2O snowline, and therefore their profiles potentially contain information which can be used to locate the position of the H2O snowline. The wavelengths of the H2O lines which are the best candidates to locate the position of the H2O snowline range from mid-infrared to sub-millimeter, and the total line fluxes tend to increase with decreasing wavelengths. We investigated the possibility of future observations using the ALMA and mid-infrared high-dispersion spectrographs (e.g., SPICA/SMI-HRS). Since the fluxes of those identified lines from a Herbig Ae disk are stronger than those of a T Tauri disk, the possibility of a successful detection is expected to increase for a Herbig Ae disk.

scholarly journals Forbidden line diagnostics of photoevaporative disc winds

2020 ◽  
Vol 496 (3) ◽  
pp. 2932-2945 ◽  
Author(s):  
G Ballabio ◽  
R D Alexander ◽  
C J Clarke
Keyword(s):  
Sound Speed ◽  
Central Star ◽  
High Energy ◽  
Emission Lines ◽  
Limiting Factor ◽  
Line Profiles ◽  
Gas Temperature ◽  
Characteristic Emission ◽  
Extreme Uv ◽  
High Sound

ABSTRACT Photoevaporation driven by high-energy radiation from the central star plays an important role in the evolution of protoplanetary discs. Photoevaporative winds have been unambiguously detected through blue-shifted emission lines, but their detailed properties remain uncertain. Here we present a new empirical approach to make observational predictions of these thermal winds, seeking to fill the gap between theory and observations. We use a self-similar model of an isothermal wind to compute line profiles of several characteristic emission lines (in particular the [Ne ii] line at 12.81 μm, and optical forbidden lines such as [O i] 6300 Å and [S ii] 4068/4076 Å), studying how the lines are affected by parameters such as the gas temperature, disc inclinations, and density profile. Our model successfully reproduces blue-shifted lines with $v_{\rm peak} \lesssim 10$ km s−1, which decrease with increasing disc inclination. The line widths increase with increasing disc inclinations and range from $\Delta v\sim 15\text{ to }30$ km s−1. The predicted blue-shifts are mostly sensitive to the gas sound speed (and therefore the temperature). The observed [Ne ii] line profiles are consistent with a thermal wind and point towards a relatively high sound speed, as expected for extreme-UV photoevaporation. However, the observed [O i] line profiles require lower temperatures, as expected in X-ray photoevaporation, and show a wider scatter that is difficult to reconcile with a single wind model; it seems likely that these lines trace different components of a multiphase wind. We also note that the spectral resolution of current observations remains an important limiting factor in these studies, and that higher resolution spectra are required if emission lines are to further our understanding of protoplanetary disc winds.

scholarly journals High Luminosity F-K Stars Motions and Hα Emissions

1980 ◽  
Vol 51 ◽  
pp. 170-170
Author(s):  
J. Smolinski ◽  
J.L. Climenhaga ◽  
B.L. Harris
Keyword(s):  
Radial Velocity ◽  
Radial Velocities ◽  
Emission Lines ◽  
High Dispersion ◽  
Common Phenomenon ◽  
Line Profiles ◽  
High Luminosity ◽  
Regular Time ◽  
Time Variations

AbstractChanges and differences in radial velocities between neutral and ionized metals have been found for three F5-type supergiants: HD 231195, HD 10494, and HD 17971. Fifteen high dispersion coudé spectrograms (6 Å/mm) were used and 33 to 165 lines were measured on each. Semi-regular time variations up to about 8 km s-1 in radial velocity have been found. In addition, Hα line profiles for 8 high luminosity F-K stars have been analyzed. All of the stars show Ha emissions, variable in time, which is probably a common phenomenon in very luminous stars. Metallic emission lines with low excitation potentials, in particular the Ca I 6572.8 and the Fe I 6574.2 lines, are present in 5 of these stars.

scholarly journals On the Photometric Behaviour of the Central Star of the Planetary Nebula Sh2–71

1993 ◽  
Vol 155 ◽  
pp. 399-399
Author(s):  
J. Jurcsik
Keyword(s):  
Planetary Nebula ◽  
Central Star ◽  
High Dispersion ◽  
Photometric System ◽  
Colour Variation ◽  
Variable Amplitude ◽  
Central Object ◽  
Spectroscopic Observations ◽  
Exciting Source ◽  
Lower Luminosity

The central star of Sh2–71 was observed with the lm telescope using UBV(RI)c photometric system at Konkoly Observatory in the seasons of 1990–92. A period of 68d.06 was found with variable amplitude and/or lightcurve shape. The amplitude is high, close to 1 magnitude. On the basis of old photographic observations (Kohoutek 1979) this period has not changed during the century. No significant colour variation was detected, but the nebular contamination should distort the colour curves. According to the five colour data the central object is a highly reddened B5 dwarf about 1700 pc distant. The nebular properties, however, indicate an evolved, higher mass, lower luminosity exciting source, therefore it is plausible to regard the central object as a binary. The light variation might be caused by obscuration of the B star by outflowing matter from the true nucleus. Bipolar outflow of 3″ dimension has been detected on high dispersion Hα spectra of the central star (Sabbadin et al. 1985; Cuesta et al. 1990). Further spectroscopic observations are highly needed in order to find the exact description of the system.

Possibility to locate the position of the H2O snowline in protoplanetary disks through spectroscopic observations

2018 ◽  
Vol 14 (S345) ◽  
pp. 393-395
Author(s):  
Shota Notsu ◽  
Hideko Nomura ◽  
Catherine Walsh ◽  
Mitsuhiko Honda ◽  
Tomoya Hirota ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Planet Formation ◽  
Protoplanetary Disks ◽  
Formation Processes ◽  
Line Profiles ◽  
Number Density ◽  
Water Line ◽  
Spectroscopic Observations ◽  
The Earth ◽  
Exact Position

AbstractObservationally locating the position of the H2O snowline in protoplanetary disks is crucial for understanding planetesimal and planet formation processes, and the origin of water on the Earth. In our studies, we conducted calculations of chemical reactions and water line profiles in protoplanetary disks, and identified that ortho/para-H216O, H218O lines with small Einstein A coefficients and relatively high upper state energies are dominated by emission from the hot midplane region inside the H2O snowline. Therefore, through analyzing their line profiles the position of the H2O snowline can be located. Moreover, because the number density of the H218O is much smaller than that of H216O, the H218O lines can trace deeper into the disk and thus they are potentially better probes of the exact position of the H2O snowline in disk midplane.

scholarly journals Searching for H2 emission from protoplanetary disks using near- and mid-infrared high-resolution spectroscopy

2007 ◽  
Vol 3 (S249) ◽  
pp. 359-368
Author(s):  
A. Carmona ◽  
M. E. van den Ancker ◽  
Th. Henning ◽  
Ya. Pavlyuchenkov ◽  
C. P. Dullemond ◽  
...  
Keyword(s):  
Surface Layer ◽  
High Resolution ◽  
Near Infrared ◽  
Protoplanetary Disks ◽  
High Resolution Spectroscopy ◽  
Disk Model ◽  
Mid Infrared ◽  
T Tauri ◽  
Hα Emission ◽  
Ir Emission

AbstractThe mass and dynamics of protoplanetary disks are dominated by molecular hydrogen (H2). However, observationally very little is known about the H2. In this paper, we discuss two projects aimed to constrain the properties of H2 in the disk's planet forming region (R<50AU). First, we present a sensitive survey for pure-rotational H2 emission at 12.278 and 17.035 μm in a sample of nearby Herbig Ae/Be and T Tauri stars using VISIR, ESO's VLT high-resolution mid-infrared spectrograph. Second, we report on a search for H2 ro-vibrational emission at 2.1228, 2.2233 and 2.2477 μm in the classical T Tauri star LkHα 264 and the debris disk 49 Cet employing CRIRES, ESO's VLT high-resolution near-infrared spectrograph.VISIR project: none of the sources show H2 mid-IR emission. The observed disks contain less than a few tenths of MJupiter of optically thin H2 at 150 K, and less than a few MEarth at T>300 K. % and higher T. Our non-detections are consistent with the low flux levels expected from the small amount of H2 gas in the surface layer of a Chiang and Goldreich (1997) Herbig Ae two-layer disk model. In our sources the H2 and dust in the surface layer have not significantly departed from thermal coupling (Tgas/Tdust<2) and the gas-to-dust ratio in the surface layer is very likely <1000.CRIRES project: The H2 lines at 2.1218 μm and 2.2233 μm are detected in LkHα 264. An upper limit on the 2.2477 μm H2 line flux in LkHα 264 is derived. 49 Cet does not exhibit H2 emission in any of observed lines. There are a few MMoon of optically thin hot H2 in the inner disk (∼0.1 AU) of LkHα 264, and less than a tenth of a MMoon of hot H2 in the inner disk of 49 Cet. The shape of the 1–0 S(0) line indicates that LkHα disk is close to face-on (i<35o). The measured 1–0 S(0)/1–0 S(1) and 2–1 S(1)/1–0 S(1) line ratios in LkHα 264 indicate that the H2 is thermally excited at T<1500 K. The lack of H2 emission in the NIR spectra of 49 Cet and the absence of Hα emission suggest that the gas in the inner disk of 49 Cet has dissipated.

scholarly journals Stellar wind flows in T Tauri stars

1987 ◽  
Vol 122 ◽  
pp. 105-106
Author(s):  
C. Sá ◽  
M.T.V.T. Lago ◽  
M.V. Penston
Keyword(s):  
Stellar Wind ◽  
General Pattern ◽  
T Tauri Stars ◽  
Emission Lines ◽  
High Dispersion ◽  
T Tauri ◽  
Wind Flows ◽  
Using Data

Following the successful modelling of the wind from RU Lupi using data at moderate and high dispersion we report on similar observations of other T Tauri stars where the general pattern of the wind, as deduced from the widths of the emission lines of the various species, seems to be similar.

Short Term Variations in the Spectrum of the T Tauri Star DI Cep

1979 ◽  
Vol 46 ◽  
pp. 369-370
Author(s):  
R. Mundt ◽  
U. Bastian
Keyword(s):  
Time Scales ◽  
Time Resolution ◽  
Equivalent Width ◽  
Tauri Star ◽  
Emission Lines ◽  
Short Term ◽  
Spectroscopic Observations ◽  
T Tauri ◽  
Time Variations ◽  
Short Time

AbstractExtended spectroscopic observations of the T Tauri star DI Cep with a time resolution of 10 to 15 minutes have been carried out. On 2 of 6 observing nights the star showed significant variations of the strengths of its emission lines on time scales down to the time resolution of the observations. The most drastic event is shown in Figure 1. The equivalent width of the Hα line increased by a factor of 7 within two hours. Even faster variations, but of smaller amplitude, were observed in the strengths of the Hβ and Till 82 (λ 4572 Å) lines on another night. Obviously strong short time variations are not always present in DI Cep, as in 4 nights no significant variations could be detected.

scholarly journals Characterization of mid-infrared polarization due to scattering in protoplanetary disks

2020 ◽  
Vol 634 ◽  
pp. A129 ◽  
Author(s):  
S. Heese ◽  
S. Wolf ◽  
R. Brauer
Keyword(s):  
Magnetic Fields ◽  
Linear Polarization ◽  
Radial Distance ◽  
Protoplanetary Disks ◽  
Field Studies ◽  
Central Star ◽  
Polarization Degree ◽  
Mid Infrared ◽  
Stellar Radiation ◽  
Linearly Polarized

Context. It is generally assumed that magnetic fields play an important role in the formation and evolution of protoplanetary disks. One way of observationally constraining magnetic fields is to measure polarized emission and absorption produced by magnetically aligned elongated dust grains. The fact that radiation also becomes linearly polarized by light scattering at optical to millimeter wavelengths complicates magnetic field studies. Aims. We characterize the linear polarization of mid-infrared radiation due to scattering of the stellar radiation and dust thermal re-emission radiation (self-scattering). Methods. We computed the radial polarization profiles at wavelengths across the N and Q bands for a broad range of circumstellar disk configurations. These simulations served as a basis to analyze the correlations between selected disk parameters and the resulting linear polarization. Results. We find that the thermal re-emission radiation is stronger than the scattered stellar radiation for disks with inner holes smaller than ~10 au within the considered parameter range. The mid-infrared polarization due to scattering shows several clear trends: for scattered stellar radiation only, the linear polarization degree decreases slightly with increasing radial distance, while it increases with radial distance for thermal re-emission radiation only and for a combination of scattered stellar radiation and thermal re-emission radiation. The linear polarization degree decreases with increasing disk flaring and luminosity of the central star. An increasing inner radius shifts the increase of the linear polarization degree further outside, while a larger scale height increases the linear polarization degree for small radial distances and decreases this degree further outside. For longer wavelengths, i.e., toward the Q band in our study, the linear polarization degree converges more slowly. Conclusions. We found several clear trends for polarization due to scattering. These trends are the basis to distinguish polarization due to scattering from polarization due to dichroic emission and absorption.

scholarly journals Spectroscopic Observations of The Be Star PHI-PER

1993 ◽  
Vol 137 ◽  
pp. 804-806
Author(s):  
Mahendra Singh ◽  
Masahiro Mon ◽  
Tomokazu Kogure ◽  
Masakazu Suzuki
Keyword(s):  
Radial Velocity ◽  
Intensity Ratio ◽  
Emission Lines ◽  
High Dispersion ◽  
Main Difficulty ◽  
Primary Star ◽  
Red Emission ◽  
Binary Nature ◽  
Spectroscopic Observations ◽  
Be Star

AbstractBased on a series of high dispersion Coude spectra taken with 188-cm telescope of Okayama Astrophysical Observatory over an extensive period of time (nearly 20 years), spectroscopic behaviours were measured and discussed. Synchronous variations of V/R (intensity ratio of violet to red emission peaksjvariability with the radial velocity curves (RV) for Balmer and Hel 3888 shell absorption lines were confirmed. Using the peak separations of the Balmer emission lines, envelope extension was also estimated. Main difficulty was found in explaining the envelope extension of the primary star of the system which overflows the Roche-lobe limit when we consider the binary nature of the system.

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