scholarly journals Zodiacal exoplanets in time – X. The orbit and atmosphere of the young ‘neptune desert’-dwelling planet K2-100b

2020 ◽  
Vol 495 (1) ◽  
pp. 650-662 ◽  
Author(s):  
E Gaidos ◽  
T Hirano ◽  
A W Mann ◽  
D A Owens ◽  
T A Berger ◽  
...  
Keyword(s):  
Mass Loss ◽  
Spherically Symmetric ◽  
Orbital Eccentricity ◽  
Origin And Evolution ◽  
Atmospheric Escape ◽  
Hyades Cluster ◽  
Solar Composition ◽  
Short Period ◽  
Elevated Activity ◽  
Core Accretion

ABSTRACT We obtained high-resolution infrared spectroscopy and short-cadence photometry of the 600–800 Myr Praesepe star K2-100 during transits of its 1.67-d planet. This Neptune-size object, discovered by the NASA K2 mission, is an interloper in the ‘desert’ of planets with similar radii on short-period orbits. Our observations can be used to understand its origin and evolution by constraining the orbital eccentricity by transit fitting, measuring the spin-orbit obliquity by the Rossiter–McLaughlin effect, and detecting any extended, escaping the hydrogen–helium envelope with the 10 830 -Å line of neutral helium in the 2s3S triplet state. Transit photometry with 1-min cadence was obtained by the K2 satellite during Campaign 18 and transit spectra were obtained with the IRD spectrograph on the Subaru telescope. While the elevated activity of K2-100 prevented us from detecting the Rossiter–McLaughlin effect, the new photometry combined with revised stellar parameters allowed us to constrain the eccentricity to e < 0.15/0.28 with 90/99 per cent confidence. We modelled atmospheric escape as an isothermal, spherically symmetric Parker wind, with photochemistry driven by ultraviolet radiation, which we estimate by combining the observed spectrum of the active Sun with calibrations from observations of K2-100 and similar young stars in the nearby Hyades cluster. Our non-detection (<5.7 m Å) of a transit-associated He i line limits mass-loss of a solar-composition atmosphere through a T ≤ 10000 K wind to <0.3 M⊕ Gyr−1. Either K2-100b is an exceptional desert-dwelling planet, or its mass-loss is occurring at a lower rate over a longer interval, consistent with a core accretion-powered scenario for escape.

Modelling of Io’s Atmosphere for the IVO Mission

2021 ◽  
Author(s):  
Peter Wurz ◽  
Audrey Vorburger ◽  
Alfred McEwen ◽  
Kathy Mandt ◽  
Ashley Davies ◽  
...  
Keyword(s):  
Mass Loss ◽  
Dynamic Range ◽  
Detection Threshold ◽  
Mass Range ◽  
Mission Design ◽  
Integration Time ◽  
Many Worlds ◽  
Initial State ◽  
Atmospheric Escape ◽  
Tidal Heating

<p>The Io Volcano Observer (IVO) is a proposed NASA Discovery-class mission (currently in Phase A), that would launch<span> in early 2029, arrive at </span> Jupiter in the early 2033, and perform ten flybys of Io while in Jupiter's orbit. IVO's mission motto is to 'follow the heat', shedding light onto tidal heating as a fundamental planetary process. Specifically, IVO will determine (i) how and where heat is generated in Io's interior, (ii) how heat is transported to the surface, and (iii) how Io has evolved with time. The answers to these questions will fill fundamental gaps in the current understanding of the evolution and habitability of many worlds across our Solar System and beyond where tidal heating plays a key role, and will give us insight into how early Earth, Moon, and Mars may have worked.</p><p>One of the five key science questions IVO will be addressing is determining Io's mass loss via atmospheric escape. Understanding Io's mass loss today will offer information on how the chemistry of Io has been altered from its initial state and would provide useful clues on how atmospheres on other bodies have evolved over time. IVO plans on measuring Io's mass loss in situ with the Ion and Neutral Mass Spectrometer (INMS), a successor to the instrument currently being built for the JUpiter Icy moons Explorer (JUICE). INMS will measure neutrals and ions in the mass range 1 – 300 u, with a mass resolution (M/ΔM) of 500, a dynamic range of > 10<sup>5</sup>, a detection threshold of 100 cm<sup>–3</sup> for an integration time of 5 s, and a cadence of 0.5 – 300 s per spectrum.</p><p>In preparation for IVO, we model atmospheric density profiles of species known and expected to be present on Io's surface from both measurements and previous modelling efforts. Based on the IVO mission design, we present three different measurement scenarios for INMS we expect to encounter at Io based on the planned flybys: (i) a purely sublimated atmosphere, (ii) the 'hot' atmosphere generated by lava fields, and (iii) the plume gases resulting from volcanic activity. We calculate the expected mass spectra to be recorded by INMS during these flybys for these atmospheric scenarios.</p>

scholarly journals ENHANCED MASS LOSS RATES IN RED SUPERGIANTS AND THEIR IMPACT ON THE CIRCUMSTELLAR MEDIUM

2019 ◽  
Vol 55 (2) ◽  
pp. 161-175
Author(s):  
L. Hernández-Cervantes ◽  
B. Pérez-Rendón ◽  
A. Santillán ◽  
G. García-Segura ◽  
C. Rodríguez-Ibarra
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Gas Dynamics ◽  
Numerical Experiments ◽  
Evolutionary Models ◽  
Solar Composition ◽  
Red Supergiants ◽  
The Impact ◽  
Circumstellar Medium ◽  
Loss Rates

In this work, we present models of massive stars between 15 and 23 M⊙ , with enhanced mass loss rates during the red supergiant phase. Our aim is to explore the impact of extreme red supergiant mass-loss on stellar evolution and on their circumstellar medium. We computed a set of numerical experiments, on the evolution of single stars with initial masses of 15, 18, 20 and, 23 M⊙ , and solar composition (Z = 0.014), using the numerical stellar code BEC. From these evolutionary models, we obtained time-dependent stellar wind parameters, that were used explicitly as inner boundary conditions in the hydrodynamical code ZEUS-3D, which simulates the gas dynamics in the circumstellar medium (CSM), thus coupling the stellar evolution to the dynamics of the CSM. We found that stars with extreme mass loss in the RSG phase behave as a larger mass stars.

scholarly journals Crossing the “Yellow Void” – Spatially Resolved Spectroscopy of the Post–Red Supergiant IRC+10420

2002 ◽  
Vol 187 ◽  
pp. 95-98
Author(s):  
Roberta M. Humphreys ◽  
Kris Davidson ◽  
Nathan Smith
Keyword(s):  
Mass Loss ◽  
Spatial Resolution ◽  
Spherically Symmetric ◽  
Bipolar Outflow ◽  
Reflection Nebula ◽  
Spatially Resolved ◽  
Spatially Resolved Spectroscopy ◽  
Rapid Mass ◽  
Hr Diagram

AbstractIRC+10420 is a post–red supergiant at the empirical luminosity boundary in the HR diagram. It has now reached a stage in its blueward evolution where increasing opacity and partial ionization destabilize its atmosphere leading to rapid mass loss. Indeed, its wind is so dense that it is opaque and hides the underlying star. We have obtained HST/STIS spectroscopy with spatial resolution good enough to separate the star from its complex ejecta with numerous arcs, knots and jet-like features. The ejecta form essentially a reflection nebula, allowing us to view the star from a range of directions. The kinematics of the ejecta cannot be reconciled with existing models with either an equatorial disk or a bipolar outflow. Therefore we propose a model with a uniform spherically symmetric outflow of gas with random, asymmetric ejections superimposed. In our model, local instabilities allow for inflowing and outflowing material to coexist.

scholarly journals X Sources in δ Scuti Stars: an Ultraviolet Study of 71 Tau

1993 ◽  
Vol 139 ◽  
pp. 396-396
Author(s):  
L.E. Pasinetti Fracassini ◽  
L. Pastori ◽  
F. De Nile ◽  
E. Poretti ◽  
E. Antonello
Keyword(s):  
Mass Loss ◽  
Spectroscopic Data ◽  
Pulsation Period ◽  
X Ray ◽  
Chromospheric Activity ◽  
Hyades Cluster ◽  
Photometric Observations ◽  
Scuti Stars ◽  
Einstein Observatory ◽  
Δ Scuti Stars

IUE observations of δ Scuti variables were planned to study the correlations between chromospheric activity and dynamics of pulsations, convection, rotation and to search for evidence of mass loss. So far we observed the following stars: ρ Pup, β Cas, o1 Eri, K2 Boo, τ Peg, 69 Tau, 71 Tau and τ Cyg. Results and discussions on our survey may be found in Pasinetti Fracassini et al. (1990) and Fracassini et al. (1991).Ultraviolet spectroscopic data (6 LWP and 3 SWP spectra) of 71 Tau were obtained with IUE in the year 1990, spanning an interval of 5h35rn and covering about 1.5 cycles of the pulsation period. The period, derived from new photometric observations, is 4h32m with an cimplitude of 0m.028. This variable is the most intense X-ray source in the Hyades cluster according to the results of Einstein Observatory.

scholarly journals High-resolution observations of gas and dust around Mira using ALMA and SPHERE/ZIMPOL

2018 ◽  
Vol 620 ◽  
pp. A75 ◽  
Author(s):  
T. Khouri ◽  
W. H. T. Vlemmings ◽  
H. Olofsson ◽  
C. Ginski ◽  
E. De Beck ◽  
...  
Keyword(s):  
Mass Loss ◽  
Polarized Light ◽  
Aluminium Oxide ◽  
Significant Fraction ◽  
Agb Stars ◽  
Dust Grains ◽  
Density Region ◽  
Gas Density ◽  
Stellar Pulsation ◽  
Solar Composition

Context. The outflows of oxygen-rich asymptotic giant branch (AGB) stars are thought to be driven by radiation pressure due to the scattering of photons on relatively large grains, with sizes of tenths of microns. The details of the formation of dust in the extended atmospheres of these stars and, therefore, the mass-loss process, is still not well understood. Aims. We aim to constrain the distribution of the gas and the composition and properties of the dust grains that form in the inner circumstellar environment of the archetypal Mira variable o Cet. Methods. We obtained quasi-simultaneous observations using ALMA and SPHERE/ZIMPOL on the Very Large Telescope (VLT) to probe the distribution of gas and large dust grains, respectively. Results. The polarized light images show dust grains around Mira A, but also around the companion, Mira B, and a dust trail that connects the two sources. The ALMA observations show that dust around Mira A is contained in a high-gas-density region with a significant fraction of the grains that produce the polarized light located at the edge of this region. Hydrodynamical and wind-driving models show that dust grains form efficiently behind shock fronts caused by stellar pulsation or convective motions. The distance at which we observe the density decline (a few tens of au) is, however, significantly larger than expected for stellar-pulsation-induced shocks. Other possibilities for creating the high-gas-density region are a recent change in the mass-loss rate of Mira A or interactions with Mira B. We are not able to determine which of these scenarios is correct. We constrained the gas density, temperature, and velocity within a few stellar radii from the star by modelling the CO v = 1, J = 3−2 line. We find a mass (~3.8 ± 1.3) × 10−4 M⊙ to be contained between the stellar millimetre photosphere, R⋆338 GHz, and 4 R⋆338 GHz. Our best-fit models with lower masses also reproduce the 13CO v = 0, J = 3−2 line emission from this region well. We find TiO2 and AlO abundances corresponding to 4.5% and <0.1% of the total titanium and aluminium expected for a gas with solar composition. The low abundance of AlO allows for a scenario in which Al depletion into dust happens already very close to the star, as expected from thermal dust emission observations and theoretical calculations of Mira variables. The relatively large abundance of aluminium for a gas with solar composition allows us to constrain the presence of aluminium oxide grains based on the scattered light observations and on the gas densities we obtain. These models imply that aluminium oxide grains could account for a significant fraction of the total aluminium atoms in this region only if the grains have sizes ≲0.02 μm. This is an order of magnitude smaller than the maximum sizes predicted by dust-formation and wind-driving models. Conclusions. The study we present highlights the importance of coordinated observations using different instruments to advance our understanding of dust nucleation, dust growth, and wind driving in AGB stars.

scholarly journals A search for radio emission from exoplanets around evolved stars

2018 ◽  
Vol 612 ◽  
pp. A52 ◽  
Author(s):  
E. O’Gorman ◽  
C. P. Coughlan ◽  
W. Vlemmings ◽  
E. Varenius ◽  
S. Sirothia ◽  
...  
Keyword(s):  
Radio Emission ◽  
Mass Loss ◽  
Low Frequency ◽  
Large Mass ◽  
Low Frequencies ◽  
Surface Magnetic Field ◽  
Evolved Stars ◽  
Upper Limits ◽  
Short Period ◽  
Loss Rates

The majority of searches for radio emission from exoplanets have to date focused on short period planets, i.e., the so-called hot Jupiter type planets. However, these planets are likely to be tidally locked to their host stars and may not generate sufficiently strong magnetic fields to emit electron cyclotron maser emission at the low frequencies used in observations (typically ≥150 MHz). In comparison, the large mass-loss rates of evolved stars could enable exoplanets at larger orbital distances to emit detectable radio emission. Here, we first show that the large ionized mass-loss rates of certain evolved stars relative to the solar value could make them detectable with the LOw Frequency ARray (LOFAR) at 150 MHz (λ = 2 m), provided they have surface magnetic field strengths >50 G. We then report radio observations of three long period (>1 au) planets that orbit the evolved stars β Gem, ι Dra, and β UMi using LOFAR at 150 MHz. We do not detect radio emission from any system but place tight 3σ upper limits of 0.98, 0.87, and 0.57 mJy on the flux density at 150 MHz for β Gem, ι Dra, and β UMi, respectively. Despite our non-detections these stringent upper limits highlight the potential of LOFAR as a tool to search for exoplanetary radio emission at meter wavelengths.

scholarly journals Period Changes and Mass Loss Rates in 34 RS CVn-Type Binaries

1980 ◽  
Vol 88 ◽  
pp. 383-387 ◽  
Author(s):  
Douglas S. Hall ◽  
Jerzy M. Kreiner ◽  
Steven N. Shore
Keyword(s):  
Light Curve ◽  
Mass Loss ◽  
Least Squares ◽  
Weighted Least Squares ◽  
Astronomical Observatory ◽  
Astronomical Institute ◽  
Long Period ◽  
Sternberg Astronomical Institute ◽  
Short Period

We have collected all available times of minimum, over 1650, for 23 regular, 7 short-period, and 4 long-period eclipsing RS CVn binaries using the card catalogues at the Sternberg Astronomical Institute and the Krakow Astronomical Observatory, as well as unpublished data. We examined them critically, discarded those grossly in error, and assigned weights. For AD Cap, RV Lib, and ε UMi there are virtually no data. For the remaining 31 we determined quadratic ephemerides by weighted least squares. Values of d1nP/dt are given in the Table with their errors. Roughly 2/3 are variable at greater than the 2 σ level. Significant decreases outnumber significant increases by almost 2:1. We show that light curve asymmetry produced by the distortion wave probably accounts for the relatively small, rapid fluctuations in the O-C curve but not the long-term period changes.

Origin and Evolution of Wolf-Rayet Stars

1982 ◽  
Vol 99 ◽  
pp. 377-381
Author(s):  
A. Tutukov ◽  
L. Yungelson
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Close Binary ◽  
Initial Mass ◽  
Convective Stability ◽  
Helium Burning ◽  
Origin And Evolution ◽  
The Core

The larger part of close binary components with initial mass exceeding ∼20 Mo becomes WR stars in the core helium burning stage. Some of the most massive WR stars may be products of evolution of single massive stars with initial masses exceeding ∼50 M0 if the mass loss in the infrared supergiant stage is effective enough. The Ledoux criterion of convective stability seems more promising to explain the observed properties of WR stars.

Modeling the Atmospheric Contribution to the Interior Characterization of sub-Neptunes and its Effect on Habitability

2020 ◽  
Author(s):  
Jasmine MacKenzie ◽  
Philipp Baumeister ◽  
Mareike Godolt ◽  
Nicola Tosi ◽  
Daria Kubyshkina ◽  
...  
Keyword(s):  
Bulk Composition ◽  
Physical Parameters ◽  
Habitable Zone ◽  
Calculated Density ◽  
Atmospheric Escape ◽  
Dense Cores ◽  
Solar Composition ◽  
Primary Composition ◽  
Low Mass

&lt;p&gt;As the number of confirmed exoplanets has increased, so too has the diversity in their physical parameters, namely their mass and radius. A common practice is to place these planets on a Mass-Radius diagram with various calculated density curves corresponding to some bulk composition. However, these lines don&amp;#8217;t necessarily correspond to the structure of the planet found using interior models, particularly for low mass planets with masses less than 20 M&lt;sub&gt;&amp;#8853;&lt;/sub&gt; and 4 R&lt;sub&gt;&amp;#8853;&lt;/sub&gt;, which we call &amp;#8220;sub-Neptunes.&amp;#8221; Planets in this range can have highly degenerate solutions with no solar system analog, from so-called &amp;#8220;ocean worlds&amp;#8221; to small dense cores with extended primary composition atmospheres. We have created a model that is able to cover the range of solutions possible for sub-Neptunes, with various levels of complexity for both the interior and atmosphere. This includes both an isothermal and semi-grey atmosphere, along with a high-pressure solar composition envelope when atmospheric pressures exceed approximately 1000 bar. We then apply this model to known sub-Neptunes located in the extended habitable zone of their star using a hydrogen-helium dominated atmosphere. An atmospheric escape model is used to investigate the longevity of the atmosphere and its effect on the overall habitability of the planet.&lt;/p&gt;

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