scholarly journals Chemical fingerprints of formation in rocky super-Earths’ data

2020 ◽  
Vol 499 (1) ◽  
pp. 932-947
Author(s):  
Mykhaylo Plotnykov ◽  
Diana Valencia
Keyword(s):  
Gaussian Distribution ◽  
Large Range ◽  
Interior Structure ◽  
Core Mass ◽  
Iron Enrichment ◽  
Chemical Fingerprints ◽  
Mass Fractions ◽  
Reference Pressure ◽  
Rocky Planets

ABSTRACT The composition of rocky exoplanets in the context of stars’ composition provides important constraints to formation theories. In this study, we select a sample of exoplanets with mass and radius measurements with an uncertainty $\lt 25{{\ \rm per\ cent}}$ and obtain their interior structure. We calculate compositional markers, ratios of iron to magnesium and silicon, as well as core mass fractions (CMFs) that fit the planetary parameters, and compare them to the stars. We find four key results that successful planet formation theories need to predict: (1) In a population sense, the composition of rocky planets spans a wider range than stars. The stars’ Fe/Si distribution is close to a Gaussian distribution $1.63^{+0.91}_{-0.85}$, while the planets’ distribution peaks at lower values and has a longer tail, $1.15^{+1.43}_{-0.76}$. It is easier to see the discrepancy in CMF space, where primordial stellar composition is $0.32^{+0.14}_{-0.12}$, while rocky planets follow a broader distribution $0.24^{+0.33}_{-0.18}$. (2) We introduce uncompressed density ($\overline{\rho _0}$ at reference pressure/temperature) as a metric to compare compositions. With this, we find what seems to be the maximum iron enrichment that rocky planets attain during formation ($\overline{\rho _0}\sim 6$ and CMF ∼0.8). (3) Highly irradiated planets exhibit a large range of compositions. If these planets are the result of atmospheric evaporation, iron enrichment and perhaps depletion must happen before gas dispersal. And, (4) We identify a group of highly irradiated planets that, if rocky, would be twofold depleted in Fe/Si with respect to the stars. Without a reliable theory for forming iron-depleted planets, these are interesting targets for follow-up.

Characterizing the possible interior structures of the nearby Exoplanets Proxima Centauri b and Ross-128 b

2020 ◽  
Vol 500 (1) ◽  
pp. 333-354
Author(s):  
Mahesh Herath ◽  
Saraj Gunesekera ◽  
Chandana Jayaratne
Keyword(s):  
Magnetic Fields ◽  
Bulk Composition ◽  
Slow Rotation ◽  
Interior Structure ◽  
Minimum Mass ◽  
Tidal Effects ◽  
Core Mass ◽  
Elemental Abundances ◽  
Red Dwarfs ◽  
Mass Fractions

ABSTRACT We developed a new numerical model to constrain the interior structure of rocky Exoplanets, and applied it to the nearby planets Proxima Centauri b and Ross-128 b. The recently measured elemental abundances of red dwarfs and Alpha Centauri were utilized to infer the bulk composition of each planet, and to measure their core mass fractions (CMFs). The results of our model predicted that the radius of Proxima b at its minimum mass may be 1.036 ± 0.040 R⊕, and if its mass is as high as 2 M⊕, 1.170 ± 0.040 R⊕. The radius of Ross-128 b at minimum mass may be 1.034 ± 0.040 R⊕, with its radius at an upper bound mass of 2 M⊕ being 1.150 ± 0.040 R⊕. Both planets may have thin mantles with similar conditions to Earth, but not convecting as vigorously. The CMFs might lie in the ranges of 20–59 per cent and 34–59 per cent for Proxima b and Ross-128 b, respectively, making it very likely they have massive iron cores. Their central temperatures may be high enough to partially melt the cores, and possibly generate magnetic fields. If they have magnetic fields at present, they are most likely to be multipolar in nature due to slow rotation speeds resulting from stellar tidal effects. The field strengths were predicted to have values of 0.06–0.23 G for Proxima b, and 0.07–0.14 G for Ross-128 b. If either planet contains more than 10 per cent of their mass in volatiles, magnetic fields would either be non-existent or very weak. The conditions of both planets may be hostile for habitability.

scholarly journals The Slow Merger of Massive Stars: Merger Types and Post-Merger Evolution

2002 ◽  
Vol 187 ◽  
pp. 245-251
Author(s):  
N. Ivanova ◽  
Ph. Podsiadlowski
Keyword(s):  
Main Sequence ◽  
Massive Stars ◽  
Close Binary System ◽  
Composition Profile ◽  
Close Binary ◽  
Interior Structure ◽  
Subsequent Evolution ◽  
Core Mass ◽  
Common Envelope ◽  
Different Response

AbstractWe study the slow merger of two massive stars inside a common envelope. The initial close binary system consists of a massive red supergiant and a main-sequence companion of a few solar masses. The merger product is a massive supergiant with an interior structure (core mass and composition profile) which is significantly different from that of a single supergiant that has evolved in isolation. Using a parameterized approach for the stream–core interaction, we modelled the merger phase and have identified three qualitatively different merger types: quiet, moderate and explosive mergers, where the differences are caused by the different response of the He burning shell. In the last two scenarios, the post-merger He abundance in the envelope is found to be substantially increased, but significant s-processing is mainly expected in the case of an explosive merger scenario. The subsequent evolution of the merger product up to the supernova stage is also discussed.

scholarly journals The Atmospheres of Extrasolar Super-Earths

2008 ◽  
Vol 4 (S253) ◽  
pp. 263-271 ◽  
Author(s):  
Eliza Miller-Ricci ◽  
Sara Seager ◽  
Dimitar Sasselov
Keyword(s):  
Parameter Space ◽  
Large Range ◽  
Theoretical Models ◽  
Radial Velocities ◽  
Atmospheric Composition ◽  
Transmission Spectra ◽  
Earth Atmosphere ◽  
Atmospheric Escape ◽  
Wide Range

AbstractExtrasolar super-Earths (1-10 M⊕) are likely to exist with a wide range of atmospheres. While a number of these planets have already been discovered through radial velocities and microlensing, it will be the discovery of the firsttransitingsuper-Earths that will open the door to a variety of follow-up observations aimed at characterizing their atmospheres. Super-Earths may fill a large range of parameter space in terms of their atmospheric composition and mass. Specifically, some of these planets may have high enough surface gravities to be able to retain large hydrogen-rich atmosphseres, while others will have lost most of their hydrogen to space over the planet's lifetime, leaving behind an atmosphere more closely resembling that of Earth or Venus. The resulting composition of the super-Earth atmosphere will therefore depend strongly on factors such as atmospheric escape history, outgassing history, and the level of stellar irradiation that it receives. Here we present theoretical models of super-Earth emission and transmission spectra for a variety of possible outcomes of super-Earth atmospheric composition ranging from hydrogen-rich to hydrogen-poor. We focus on how observations can be used to differentiate between the various scenarios and constrain atmospheric composition.

scholarly journals Diversity of supernovae and impostors shortly after explosion

2019 ◽  
Vol 621 ◽  
pp. A109 ◽  
Author(s):  
I. Boian ◽  
J. H. Groh
Keyword(s):  
Radiative Transfer ◽  
Shock Front ◽  
Massive Star ◽  
Large Range ◽  
Massive Stars ◽  
Early Time ◽  
Core Collapse ◽  
Binary Evolution ◽  
Cno Abundances

Observational surveys are now able to detect an increasing number of transients, such as core-collapse supernovae (SN) and powerful non-terminal outbursts (SN impostors). Dedicated spectroscopic facilities can follow up these events shortly after detection. Here we investigate the properties of these explosions at early times. We use the radiative transfer code CMFGEN to build an extensive library of spectra simulating the interaction of supernovae and their progenitor’s wind or circumstellar medium (CSM). We have considered a range of progenitor mass-loss rates (Ṁ = 5 × 10−4−10−2 M⊙ yr−1), abundances (solar, CNO-processed, and He-rich), and SN luminosities (L = 1.9 × 108 − 2.5 × 1010 L⊙). The models simulate events approximately one day after explosion, and we assume a fixed location of the shock front as Rin = 8.6 × 1013 cm. We show that the large range of massive star properties at the pre-SN stage causes a diversity of early-time interacting SN and impostors. We identify three main classes of early-time spectra consisting of relatively high-ionisation (e.g. He II and O VI), medium-ionisation (e.g. C III and N III), and low-ionisation lines (e.g. He I and Fe II/III). They are regulated by L and the CSM density. Given a progenitor wind velocity υ∞, our models also place a lower limit of Ṁ ≳ 5 × 10−4 (υ∞/150 km s−1) M⊙ yr−1 for detection of CSM interaction signatures in observed spectra. Early-time SN spectra should provide clear constraints on progenitors by measuring H, He, and CNO abundances if the progenitors come from single stars. The connections are less clear considering the effects of binary evolution. Nevertheless, our models provide a clear path for linking the final stages of massive stars to their post-explosion spectra at early times, and guiding future observational follow-up of transients with facilities such as the Zwicky Transient Facility.

scholarly journals Verifying the Use of Supernovae as Probes of the Cosmic Expansion

2005 ◽  
Vol 201 ◽  
pp. 231-240
Author(s):  
Richard Ellis ◽  
Mark Sullivan
Keyword(s):  
Large Range ◽  
Hubble Space Telescope ◽  
Light Curves ◽  
Host Galaxy ◽  
Hubble Diagram ◽  
Galaxy Type ◽  
Significant Difference ◽  
Type Ia ◽  
Ia Supernovae

We present preliminary results of a follow-up survey which aims to characterise in detail those galaxies which hosted Type Ia supernovae found by the Supernova Cosmology Project. Our survey has two components: Hubble Space Telescope imaging with STIS and Keck spectroscopy with ESI, the goal being to classify each host galaxy into one of three broad morphological/spectral classes and hence to investigate the dependence of supernovae properties on host galaxy type over a large range in redshift. Of particular interest is the supernova Hubble diagram characterised by host galaxy class which suggests that most of the scatter arises from those occurring in late-type irregulars. Supernovae hosted by (presumed dust-free) E/SO galaxies closely follow the adopted SCP cosmological model. Although larger datasets are required, we cannot yet find any significant difference in the light curves of distant supernovae hosted in different galaxy types.

scholarly journals Most super-Earths formed by dry pebble accretion are less massive than 5 Earth masses

2020 ◽  
Vol 644 ◽  
pp. A174
Author(s):  
Julia Venturini ◽  
Octavio Miguel Guilera ◽  
María Paula Ronco ◽  
Christoph Mordasini
Keyword(s):  
Mass Loss ◽  
Size Distribution ◽  
Growth Patterns ◽  
Parameter Study ◽  
Core Mass ◽  
Low Viscosity ◽  
Advection Diffusion Equation ◽  
Rocky Planets ◽  
Atmospheric Mass ◽  
Second Peak

Aims. The goal of this work is to study the formation of rocky planets by dry pebble accretion from self-consistent dust-growth models. In particular, we aim to compute the maximum core mass of a rocky planet that can sustain a thin H-He atmosphere to account for the second peak of the Kepler size distribution. Methods. We simulate planetary growth by pebble accretion inside the ice line. The pebble flux is computed self-consistently from dust growth by solving the advection–diffusion equation for a representative dust size. Dust coagulation, drift, fragmentation, and sublimation at the water ice line are included. The disc evolution is computed solving the vertical and radial structure for standard α-discs with photoevaporation from the central star. The planets grow from a moon-mass embryo by silicate pebble accretion and gas accretion. We perform a parameter study to analyse the effect of a different initial disc mass, α-viscosity, disc metallicity, and embryo location. We also test the effect of considering migration versus an in situ scenario. Finally, we compute atmospheric mass loss due to evaporation over 5 Gyr of evolution. Results. We find that inside the ice line, the fragmentation barrier determines the size of pebbles, which leads to different planetary growth patterns for different disc viscosities. We also find that in this inner disc region, the pebble isolation mass typically decays to values below 5 M⊕ within the first million years of disc evolution, limiting the core masses to that value. After computing atmospheric mass loss, we find that planets with cores below ~4 M⊕ become completely stripped of their atmospheres, and a few 4–5 M⊕ cores retain a thin atmosphere that places them in the “gap” or second peak of the Kepler size distribution. In addition, a few rare objects that form in extremely low-viscosity discs accrete a core of 7 M⊕ and equal envelope mass, which is reduced to 3–5 M⊕ after evaporation. These objects end up with radii of ~6–7 R⊕. Conclusions. Overall, we find that rocky planets form only in low-viscosity discs (α ≲ 10−4). When α ≥ 10−3, rocky objects do not grow beyond 1 Mars mass. For the successful low-viscosity cases, the most typical outcome of dry pebble accretion is terrestrial planets with masses spanning from that of Mars to ~4 M⊕.

scholarly journals Interior structure models of terrestrial exoplanets and application to CoRoT-7 b

2009 ◽  
Vol 5 (H15) ◽  
pp. 708-709
Author(s):  
Frank W. Wagner ◽  
Frank Sohl ◽  
Heike Rauer ◽  
Hauke Hussmann ◽  
Matthias Grott
Keyword(s):  
Mass Fraction ◽  
Total Mass ◽  
Terrestrial Planet ◽  
Iron Core ◽  
Interior Structure ◽  
Magma Ocean ◽  
Mineral Phase ◽  
Core Mass ◽  
Near Surface ◽  
Deep Interior

AbstractIn this study, we model the internal structure of CoRoT-7b, considered as a typical extrasolar terrestrial planet, using mass and energy balance constraints. Our results suggest that the deep interior is predominantly composed of dry silicate rock, similar to the Earth's Moon. A central iron core, if present, would be relatively small and less massive (<15 wt.% of the planet's total mass) as compared to the Earth's (core mass fraction 32.6 wt.%). Furthermore, a partly molten near-surface magma ocean could be maintained, provided surface temperatures were high enough and the rock component mainly composed of Earth-like mineral phase assemblages.

scholarly journals Interior structure models and fluid Love numbers of exoplanets in the super-Earth regime

2018 ◽  
Vol 615 ◽  
pp. A39 ◽  
Author(s):  
C. Kellermann ◽  
A. Becker ◽  
R. Redmer
Keyword(s):  
Extrasolar Planets ◽  
Water Layer ◽  
Parameter Study ◽  
Interior Structure ◽  
Tidal Interactions ◽  
Love Numbers ◽  
Mass Fractions ◽  
Successful Technique ◽  
Outer Water ◽  
Measured Mass

Space missions such as CoRoT and Kepler have made the transit method the most successful technique in observing extrasolar planets. However, although the mean density of a planet can be derived from its measured mass and radius, no details about its interior structure, such as the density profile, can be inferred so far. If determined precisely enough, the shape of the transiting light curve might, in principle, reveal the shape of the planet, and in particular, its deviation from spherical symmetry. These deformations are caused, for instance, by the tidal interactions of the planet with the host star and by other planets that might orbit in the planetary system. The deformations depend on the interior structure of the planet and its composition and can be parameterized as Love numbers kn. This means that the diversity of possible interior models for extrasolar planets might be confined by measuring this quantity. We present results of a wide-ranging parameter study in planet mass, surface temperature, and layer mass fractions on such models for super-Earths and their corresponding Love numbers. Based on these data, we find that k2 is most useful in assessing the ratio of rocky material to iron and in ruling out certain compositional configurations for measured mass and radius values, such as a prominent core consisting of rocky material. Furthermore, we apply the procedure to exoplanets K2-3b and c and predict that K2-3c probably has a thick outer water layer.

scholarly journals Possible periodic activity in the repeating FRB 121102

2020 ◽  
Vol 495 (4) ◽  
pp. 3551-3558 ◽  
Author(s):  
K M Rajwade ◽  
M B Mickaliger ◽  
B W Stappers ◽  
V Morello ◽  
D Agarwal ◽  
...  
Keyword(s):  
Large Range ◽  
Radio Bursts ◽  
Periodic Activity ◽  
Radio Monitoring ◽  
Periodic Behaviour ◽  
Long Term Monitoring ◽  
Term Monitoring ◽  
High Cadence

ABSTRACT The discovery that at least some Fast Radio Bursts (FRBs) repeat has ruled out cataclysmic events as the progenitors of these particular bursts. FRB 121102 is the most well-studied repeating FRB but despite extensive monitoring of the source, no underlying pattern in the repetition has previously been identified. Here, we present the results from a radio monitoring campaign of FRB 121102 using the 76 m Lovell telescope. Using the pulses detected in the Lovell data along with pulses from the literature, we report a detection of periodic behaviour of the source over the span of 5 yr of data. We predict that the source is currently ‘off’ and that it should turn ‘on’ for the approximate MJD range 59002−59089 (2020 June 2 to 2020 August 28). This result, along with the recent detection of periodicity from another repeating FRB, highlights the need for long-term monitoring of repeating FRBs at a high cadence. Using simulations, we show that one needs at least 100 h of telescope time to follow-up repeating FRBs at a cadence of 0.5–3 d to detect periodicities in the range of 10–150 d. If the period is real, it shows that repeating FRBs can have a large range in their activity periods that might be difficult to reconcile with neutron star precession models.

scholarly journals On the importance of including devolatilized stellar abundances in determining the composition of rocky exoplanets

2021 ◽  
Author(s):  
Fabian Seidler ◽  
Haiyang Wang ◽  
Sascha Quanz
Keyword(s):  
Mass Fraction ◽  
Terrestrial Planets ◽  
Chemical Compositions ◽  
Posterior Distributions ◽  
Stellar Abundances ◽  
Core Mass ◽  
The Core ◽  
Planetary Mass ◽  
Before And After ◽  
Mass Fractions

&lt;p&gt;Since stars and their planets form from the same molecular clouds, stellar chemical composition can be informative, to first order, of planetary bulk chemistry. An important feature of terrestrial planets compared to their host stars is the depletion of volatiles, the most important being oxygen. Previous studies on planet interiors focus on the mass and radius constraints and/or the host stellar refractory elements (e.g. Fe, Si and Mg), neglecting devolatilisation and its impact on the final picture of planet mineralogy and structure. This work assesses to what extent the devolatilised stellar abundances reflect rocky planetary composition.&amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;We firstly test how the uncertainties associated with planetary mass and radius would affect the modelling results of core mass fraction &amp;#8211; an important interior parameter. To do so, we choose the Sun-like star Kepler-21 (stellar abundance uncertainties &lt;0.05 dex) as a case study and assume it hosts an Earth-mass-and-radius planet in its habitable zone. We then assign different levels of uncertainties to the mass and radius of the hypothetical planet, ranging from 0.1% to 20%. We find that with increasing uncertainty level, the modelling result of core mass fraction constrained by the devolatilised stellar abundances and mass and radius becomes identical with the core mass fraction constrained purely by the devolatilised stellar abundances. This reveals the increased modelling degeneracy with growing uncertainties in mass and radius measurements, but also the strong constraints placed by using the devolatilised stellar abundances.&lt;/p&gt;&lt;p&gt;We further investigate a sample of 12 confirmed exoplanets, which are all less than 10 Earth masses and 2 Earth radii &amp;#8211; i.e. potentially terrestrial planets or super-Earths &amp;#8211; and with the measured uncertainties in mass and radius respectively less than 35% and 10%. By comparing the prior and posterior distributions of mass and radius before and after introducing the devolatilised stellar abundances as another prior, we find that the posterior distributions of all samples, but 55 Cnc e and Kepler-107 c, can be sampled within the 2&amp;#963; ranges of the prior distributions. For the two exceptional cases, it means that the devolatilised stellar abundances and the measured mass and radius are not compatible within the level of 2&amp;#963;.&lt;/p&gt;&lt;p&gt;We also find a diverse distribution of the core mass fractions of the sample from 0% (i.e. coreless) up to 40%, which are consistent at the 2&amp;#963; level &amp;#61472;with the core mass fractions purely constrained by mass and radius measurements (except Kepler-107 c and 55 Cnc e),&amp;#160; but are significantly constrained by adding the devolatilized stellar abundances. In contrast, the previous study for the similar sample shows nearly constant core mass fractions of ~ 30% based on the unaltered stellar abundances and by assuming 100% Fe sunk into the core (i.e. free of consideration of the oxidation state of the planets). We emphasise that to break the degeneracies of terrestrial-type exoplanet interior modelling, we must use well the currently available observables including planetary mass and radius and host stellar chemical compositions, but they must be viewed through the lens of planet formation&amp;#160; and the resulting devolatilization.&lt;/p&gt;

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