scholarly journals A data-driven approach to constraining the atmospheric temperature structure of the ultra-hot Jupiter KELT-9b

2020 ◽  
Vol 643 ◽  
pp. A131
Author(s):  
L. Fossati ◽  
D. Shulyak ◽  
A. G. Sreejith ◽  
T. Koskinen ◽  
M. E. Young ◽  
...  
Keyword(s):  
Mass Loss ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Mass Loss Rate ◽  
Atmospheric Temperature ◽  
High Mass ◽  
Temperature Structure ◽  
Hot Jupiters ◽  
Data Driven Approach ◽  
Hot Jupiter

Context. Observationally constraining the atmospheric temperature-pressure (TP) profile of exoplanets is an important step forward for improving planetary atmosphere models, thus further enabling one to place the detection of spectral features and the measurement of atomic and molecular abundances through transmission and emission spectroscopy on solid ground. Aims. The aim is to constrain the TP profile of the ultra-hot Jupiter KELT-9b by fitting synthetic spectra to the observed Hα and Hβ lines and identify why self-consistent planetary TP models are unable to fit the observations. Methods. We constructed 126 one-dimensional TP profiles varying the lower and upper atmospheric temperatures, as well as the location and gradient of the temperature rise. For each TP profile, we computed the transmission spectra of the Hα and Hβ lines employing the Cloudy radiative transfer code, which self-consistently accounts for non-local thermodynamic equilibrium (NLTE) effects. Results. The TP profiles, leading to best fit the observations, are characterised by an upper atmospheric temperature of 10 000–11 000 K and by an inverted temperature profile at pressures higher than 10−4 bar. We find that the assumption of local thermodynamic equilibrium (LTE) leads one to overestimate the level population of excited hydrogen by several orders of magnitude and hence to significantly overestimate the strength of the Balmer lines. The chemical composition of the best fitting models indicate that the high upper atmospheric temperature is most likely driven by metal photoionisation and that FeII and FeIII have comparable abundances at pressures lower than 10−6 bar, possibly making the latter detectable. Conclusions. Modelling the atmospheres of ultra-hot Jupiters requires one to account for metal photoionisation. The high atmospheric mass-loss rate (>1011 g s−1), caused by the high temperature, may have consequences on the planetary atmospheric evolution. Other ultra-hot Jupiters orbiting early-type stars may be characterised by similarly high upper atmospheric temperatures and hence high mass-loss rates. This may have consequences on the basic properties of the observed planets orbiting hot stars.

scholarly journals Chemical content of the circumstellar envelope of the oxygen-rich AGB star R Doradus

2018 ◽  
Vol 609 ◽  
pp. A63 ◽  
Author(s):  
M. Van de Sande ◽  
L. Decin ◽  
R. Lombaert ◽  
T. Khouri ◽  
A. de Koter ◽  
...  
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Central Star ◽  
High Mass ◽  
Circumstellar Envelope ◽  
Gaussian Profile ◽  
Macro Scale ◽  
Abundance Profile ◽  
Envelope Model

Context. The stellar outflows of low- to intermediate-mass stars are characterised by a rich chemistry. Condensation of molecular gas species into dust grains is a key component in a chain of physical processes that leads to the onset of a stellar wind. In order to improve our understanding of the coupling between the micro-scale chemistry and macro-scale dynamics, we need to retrieve the abundance of molecules throughout the outflow. Aims. Our aim is to determine the radial abundance profile of SiO and HCN throughout the stellar outflow of R Dor, an oxygen-rich AGB star with a low mass-loss rate. SiO is thought to play an essential role in the dust-formation process of oxygen-rich AGB stars. The presence of HCN in an oxygen-rich environment is thought to be due to non-equilibrium chemistry in the inner wind. Methods. We analysed molecular transitions of CO, SiO, and HCN measured with the APEX telescope and all three instruments on the Herschel Space Observatory, together with data available in the literature. Photometric data and the infrared spectrum measured by ISO-SWS were used to constrain the dust component of the outflow. Using both continuum and line radiative transfer methods, a physical envelope model of both gas and dust was established. We performed an analysis of the SiO and HCN molecular transitions in order to calculate their abundances. Results. We have obtained an envelope model that describes the dust and the gas in the outflow, and determined the abundance of SiO and HCN throughout the region of the stellar outflow probed by our molecular data. For SiO, we find that the initial abundance lies between 5.5 × 10-5 and 6.0 × 10-5 with respect to H2. The abundance profile is constant up to 60 ± 10 R∗, after which it declines following a Gaussian profile with an e-folding radius of 3.5 ± 0.5 × 1013 cm or 1.4 ± 0.2 R∗. For HCN, we find an initial abundance of 5.0 × 10-7 with respect to H2. The Gaussian profile that describes the decline starts at the stellar surface and has an e-folding radius re of 1.85 ± 0.05 × 1015 cm or 74 ± 2 R∗. Conclusions. We cannot unambiguously identify the mechanism by which SiO is destroyed at 60 ± 10 R∗. The initial abundances found are higher than previously determined (except for one previous study on SiO), which might be due to the inclusion of higher-J transitions. The difference in abundance for SiO and HCN compared to high mass-loss rate Mira star IK Tau might be due to different pulsation characteristics of the central star and/or a difference in dust condensation physics.

scholarly journals An ALMA view of SO and SO2 around oxygen-rich AGB stars

2020 ◽  
Vol 494 (1) ◽  
pp. 1323-1347 ◽  
Author(s):  
T Danilovich ◽  
A M S Richards ◽  
L Decin ◽  
M Van de Sande ◽  
C A Gottlieb
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Energy Levels ◽  
High Mass ◽  
High Angular Resolution ◽  
Circumstellar Envelope ◽  
Agb Stars ◽  
Abundance Distribution ◽  
High Mass Loss

ABSTRACT We present and analyse SO and SO2, recently observed with high angular resolution and sensitivity in a spectral line survey with ALMA, for two oxygen-rich AGB stars: the low mass-loss rate R Dor and high mass-loss rate IK Tau. We analyse 8 lines of SO detected towards both stars, 78 lines of SO2 detected towards R Dor, and 52 lines of SO2 detected towards IK Tau. We detect several lines of 34SO, 33SO, and 34SO2 towards both stars, and tentatively S18O towards R Dor, and hence derive isotopic ratios for these species. The spatially resolved observations show us that the two sulphur oxides are co-located towards R Dor and trace out the same wind structures in the circumstellar envelope. Much of the emission is well reproduced with a Gaussian abundance distribution spatially centred on the star. Emission from the higher energy levels of SO and SO2 towards R Dor provides evidence in support of a rotating inner region of gas identified in earlier work. The new observations allow us to refine the abundance distribution of SO in IK Tau derived from prior observations with single antennas, and confirm that the distribution is shell like with the peak in the fractional abundance not centred on the star. The confirmation of different types of SO abundance distributions will help fine-tune chemical models and allows for an additional method to discriminate between low and high mass-loss rates for oxygen-rich AGB stars.

scholarly journals Close binary models for Luminous Blue Variable stars

1989 ◽  
Vol 113 ◽  
pp. 185-194
Author(s):  
J. S. Gallagher
Keyword(s):  
Mass Loss ◽  
Binary Stars ◽  
Mass Loss Rate ◽  
Variable Stars ◽  
High Mass ◽  
Close Binary ◽  
Close Binaries ◽  
System A ◽  
Close Binary Stars ◽  
High Mass Loss

AbstractThe evolution of massive close binary stars inevitably involves mass exchange between the two stellar components as well as mass loss from the system. A combination of these two processes could produce the stellar wind-modulated behavior seen in LB Vs. The possibility that LBVs are powered by accretion is examined, and does not appear to be a satisfactory general model. Instead, identification of LBVs with close binaries in high mass-loss rate or common envelope evolutionary phases shows promise.

scholarly journals ALMA spectral line and imaging survey of a low and a high mass-loss rate AGB star between 335 and 362 GHz

2019 ◽  
Vol 621 ◽  
pp. C2
Author(s):  
L. Decin ◽  
A. M. S. Richards ◽  
T. Danilovich ◽  
W. Homan ◽  
J. A. Nuth
Keyword(s):  
Spectral Line ◽  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
High Mass ◽  
High Mass Loss

scholarly journals The Circumstellar Structure Around Supernovae

1988 ◽  
Vol 101 ◽  
pp. 15-18
Author(s):  
P. Lundqvist ◽  
C. Fransson
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Time Dependent ◽  
Temperature Structure ◽  
Radio Observations ◽  
Turn On ◽  
Sn 1987A ◽  
Circumstellar Medium

AbstractThe time dependent ionization and temperature structure of the circumstellar medium around supernovae has been calculated, in order to interpret recent supernova radio observations. For a stellar wind origin of the circumstellar medium, we relate the time of radio turn-on to the progenitor mass loss rate. We also show that large column densities for the UV resonance lines are expected. The results are applied to SN 1979c, SN 1980k and SN 1987A.

scholarly journals The estimate of hot Jupiter mass loss rate in the interaction with CME from a solar type star

2015 ◽  
Vol 11 (S320) ◽  
pp. 224-229
Author(s):  
Dmitry V. Bisikalo ◽  
Alexander A. Cherenkov ◽  
Pavel V. Kaygorodov
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Type Star ◽  
Dynamic Simulations ◽  
Solar Type ◽  
Mass Ejection ◽  
Maximum Mass Loss ◽  
Solar Type Star ◽  
Hot Jupiter

AbstractWe consider the influence of a coronal mass ejection (CME) of a solar type star on the mass loss rate of a hot Jupiter exoplanet. We have conducted 3D numerical gas-dynamic simulations of the planet's atmosphere that interacts with CME. Using the results of these simulations we have estimated the specific parameters that influence the mass loss rate. Based on the assumption that CME totally sweeps away part of the planet's gaseous envelope located outside the Roche lobe we estimated the maximum mass loss rate. Finally, we have considered the dependence of mass loss rate on the frequency of CMEs in course of star's evolution.

scholarly journals Wolf-Rayet stars in starbursts: Effects of a change of mass loss rate

1995 ◽  
Vol 163 ◽  
pp. 318-319
Author(s):  
G. Meynet
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
High Mass ◽  
New Models ◽  
Theoretical Predictions ◽  
High Mass Loss ◽  
Low Metallicity ◽  
Loss Rates

We present here starburst models based on the most recent grids of stellar evolutionary tracks obtained by the Geneva group. These new models, computed with enhanced mass loss rates during the main sequence and the Wolf-Rayet WNL phases, very well reproduce the luminosities, surface abundances and statistics of WR stars (Maeder & Meynet 1994). This change of the mass loss rates considerably affects the way the WR stars, born in a starburst's episode, are distributed among the different WR subtypes. We compare the theoretical predictions with recent observations and conclude that: (1) to reproduce the high observed ratios of WNL to O-type stars, a flat IMF seems to be required; and (2) the models which reproduce the best the observed characteristics of WR stars, i.e., those computed with an enhanced mass loss rate, can also account for the observed properties of the WR populations observed in starbursts. Moreover, the possible presence of numerous WC stars found in the low metallicity He2-10 A starburst by Vacca and Conti (1992), can only be accounted for when the high mass loss rate stellar models are used.

scholarly journals Dust Driven Mass Loss from Pulsating AGB-Stars

1993 ◽  
Vol 155 ◽  
pp. 364-364
Author(s):  
E.A. Dorfi ◽  
M.U. Feuchtinger ◽  
S. Höfner
Keyword(s):  
Shock Waves ◽  
Mass Loss ◽  
Mass Loss Rate ◽  
Numerical Procedure ◽  
Stellar Atmospheres ◽  
Stellar Winds ◽  
Temperature Structure ◽  
Cooling Zone ◽  
Grid Points ◽  
Slow Wind

A new numerical method allows an acurate calculation of the radiation hydrodynamics of time dependent stellar winds including also the radiation pressure on newly formed dust grains. The numerical procedure is based on an adaptive grid which distributes the grid points at locations of large gradients. All equations are written in conservation form and a monotonic 2. order transport scheme is used to advect the physical variables through the cell boundaries. We are able to resolve the shock waves running through the stellar atmospheres. These waves are generated by a pulsating star which is simulated by a moving piston. The following plots show the radial velocity and temperature structure of an extended atmosphere and several shock waves are clearly seen. Note that the innermost shock waves is a so-called supercritical shock where the radiative cooling zone behind the wave is clearly visible. The outer waves are almost isothermal because the material is optically thin in this region. The stellar parameters of this example are given by M = 1.2 M⊙, L = 5315L⊙ and R = 270R⊙ and the period of the moving piston is fixed at 350 days yielding a massive and slow wind with a mass loss rate of · = 1.24 10−6M⊙ yr−1 and a final velocity of v = 7.7 km s−1.

scholarly journals The nature of stellar winds in the star-disk interaction

2007 ◽  
Vol 3 (S243) ◽  
pp. 299-306 ◽  
Author(s):  
Sean Matt ◽  
Ralph E. Pudritz
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
T Tauri Stars ◽  
High Mass ◽  
Stellar Winds ◽  
Accretion Process ◽  
T Tauri ◽  
High Mass Loss

AbstractStellar winds may be important for angular momentum transport from accreting T Tauri stars, but the nature of these winds is still not well-constrained. We present some simulation results for hypothetical, hot (∼ 106 K) coronal winds from T Tauri stars, and we calculate the expected emission properties. For the high mass loss rates required to solve the angular momentum problem, we find that the radiative losses will be much greater than can be powered by the accretion process. We place an upper limit to the mass loss rate from accretion-powered coronal winds of ∼ 10−11M yr−1. We conclude that accretion powered stellar winds are still a promising scenario for solving the stellar angular momentum problem, but the winds must be cool (e.g., 104 K) and thus are not driven by thermal pressure.

Sign in / Sign up

Export Citation Format

Share Document