Pub Date : 2020-06-12DOI: 10.1051/0004-6361/202038363
I. Shaikhislamov, L. Fossati, M. Khodachenko, H. Lammer, A. G. Muñoz, A. Youngblood, N. Dwivedi, M. Rumenskikh
Aims: We aim at constraining the conditions of the wind and high-energy emission of the host star reproducing the non-detection of Ly$alpha$ planetary absorption. Methods: We model the escaping planetary atmosphere, the stellar wind, and their interaction employing a multi-fluid, three-dimensional hydrodynamic code. We assume a planetary atmosphere composed of hydrogen and helium. We run models varying the stellar high-energy emission and stellar mass-loss rate, further computing for each case the Ly$alpha$ synthetic planetary atmospheric absorption and comparing it with the observations. Results: We find that a non-detection of Ly$alpha$ in absorption employing the stellar high-energy emission estimated from far-ultraviolet and X-ray data requires a stellar wind with a stellar mass-loss rate about six times lower than solar. This result is a consequence of the fact that, for $pi$ Men c, detectable Ly$alpha$ absorption can be caused exclusively by energetic neutral atoms, which become more abundant with increasing the velocity and/or the density of the stellar wind. By considering, instead, that the star has a solar-like wind, the non-detection requires a stellar ionising radiation about four times higher than estimated. This is because, despite the fact that a stronger stellar high-energy emission ionises hydrogen more rapidly, it also increases the upper atmosphere heating and expansion, pushing the interaction region with the stellar wind farther away from the planet, where the planet atmospheric density that remains neutral becomes smaller and the production of energetic neutral atoms less efficient. Conclusions: Comparing the results of our grid of models with what is expected and estimated for the stellar wind and high-energy emission, respectively, we support the idea that the atmosphere of $pi$ Men c is likely not hydrogen-dominated.
目的:我们的目的是限制主星的风和高能发射的条件，再现Ly $alpha$行星吸收的未检测。方法:采用多流体的三维流体力学代码模拟逃逸的行星大气、恒星风及其相互作用。我们假设行星大气层是由氢和氦组成的。我们运行不同恒星高能发射和恒星质量损失率的模型，进一步计算每一种情况下Ly $alpha$合成行星大气吸收，并将其与观测结果进行比较。结果:我们发现，利用远紫外和x射线数据估计的恒星高能发射，在吸收中不检测Ly $alpha$需要恒星风，恒星质量损失率约为太阳的六分之一。这个结果是这样一个事实的结果:对于$pi$ Men c，可探测到的Ly $alpha$的吸收完全是由高能中性原子引起的，这些中性原子随着恒星风的速度和/或密度的增加而变得更加丰富。相反，考虑到这颗恒星有类似太阳的风，不被探测到需要比估计高4倍的恒星电离辐射。这是因为，尽管更强的恒星高能发射能更快地电离氢，但它也会增加高层大气的加热和膨胀，使与恒星风相互作用的区域远离行星，在那里，保持中性的行星大气密度变得更小，高能中性原子的产生效率更低。结论:将我们的模型网格的结果与对恒星风和高能辐射的预期和估计结果进行比较，我们支持$pi$ Men c的大气可能不是以氢为主的观点。
{"title":"Three-dimensional hydrodynamic simulations of the upper atmosphere of π Men c: Comparison with Lyα transit observations","authors":"I. Shaikhislamov, L. Fossati, M. Khodachenko, H. Lammer, A. G. Muñoz, A. Youngblood, N. Dwivedi, M. Rumenskikh","doi":"10.1051/0004-6361/202038363","DOIUrl":"https://doi.org/10.1051/0004-6361/202038363","url":null,"abstract":"Aims: We aim at constraining the conditions of the wind and high-energy emission of the host star reproducing the non-detection of Ly$alpha$ planetary absorption. Methods: We model the escaping planetary atmosphere, the stellar wind, and their interaction employing a multi-fluid, three-dimensional hydrodynamic code. We assume a planetary atmosphere composed of hydrogen and helium. We run models varying the stellar high-energy emission and stellar mass-loss rate, further computing for each case the Ly$alpha$ synthetic planetary atmospheric absorption and comparing it with the observations. Results: We find that a non-detection of Ly$alpha$ in absorption employing the stellar high-energy emission estimated from far-ultraviolet and X-ray data requires a stellar wind with a stellar mass-loss rate about six times lower than solar. This result is a consequence of the fact that, for $pi$ Men c, detectable Ly$alpha$ absorption can be caused exclusively by energetic neutral atoms, which become more abundant with increasing the velocity and/or the density of the stellar wind. By considering, instead, that the star has a solar-like wind, the non-detection requires a stellar ionising radiation about four times higher than estimated. This is because, despite the fact that a stronger stellar high-energy emission ionises hydrogen more rapidly, it also increases the upper atmosphere heating and expansion, pushing the interaction region with the stellar wind farther away from the planet, where the planet atmospheric density that remains neutral becomes smaller and the production of energetic neutral atoms less efficient. Conclusions: Comparing the results of our grid of models with what is expected and estimated for the stellar wind and high-energy emission, respectively, we support the idea that the atmosphere of $pi$ Men c is likely not hydrogen-dominated.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86400958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-07DOI: 10.1051/0004-6361/202038042
Natacha Brugger, R. Burn, G. Coleman, Y. Alibert, W. Benz
In the core accretion scenario, a massive core forms first and then accretes an envelope. When discussing how this core forms some divergences appear. First scenarios of planet formation predict the accretion of km-sized bodies, called planetesimals, while more recent works suggest growth by accretion of pebbles, which are cm-sized objects. These two accretion models are often discussed separately and we aim here at comparing the outcomes of the two models with identical initial conditions. We use two distinct codes: one computing planetesimal accretion, the other pebble accretion. Using a population synthesis approach, we compare planet simulations and study the impact of the two solid accretion models, focussing on the formation of single planets. We find that the planetesimal model predicts the formation of more giant planets, while the pebble accretion model forms more super-Earth mass planets. This is due to the pebble isolation mass concept, which prevents planets formed by pebble accretion to accrete gas efficiently before reaching Miso. This translates into a population of planets that are not heavy enough to accrete a consequent envelope but that are in a mass range where type I migration is very efficient. We also find higher gas mass fractions for a given core mass for the pebble model compared to the planetesimal one caused by luminosity differences. This also implies planets with lower densities which could be confirmed observationally. Focusing on giant planets, we conclude that the sensitivity of their formation differs: for the pebble accretion model, the time at which the embryos are formed, as well as the period over which solids are accreted strongly impact the results, while for the planetesimal model it depends on the planetesimal size and on the splitting in the amount of solids available to form planetesimals.
{"title":"Pebbles versus planetesimals","authors":"Natacha Brugger, R. Burn, G. Coleman, Y. Alibert, W. Benz","doi":"10.1051/0004-6361/202038042","DOIUrl":"https://doi.org/10.1051/0004-6361/202038042","url":null,"abstract":"In the core accretion scenario, a massive core forms first and then accretes an envelope. When discussing how this core forms some divergences appear. First scenarios of planet formation predict the accretion of km-sized bodies, called planetesimals, while more recent works suggest growth by accretion of pebbles, which are cm-sized objects. These two accretion models are often discussed separately and we aim here at comparing the outcomes of the two models with identical initial conditions. We use two distinct codes: one computing planetesimal accretion, the other pebble accretion. Using a population synthesis approach, we compare planet simulations and study the impact of the two solid accretion models, focussing on the formation of single planets. We find that the planetesimal model predicts the formation of more giant planets, while the pebble accretion model forms more super-Earth mass planets. This is due to the pebble isolation mass concept, which prevents planets formed by pebble accretion to accrete gas efficiently before reaching Miso. This translates into a population of planets that are not heavy enough to accrete a consequent envelope but that are in a mass range where type I migration is very efficient. We also find higher gas mass fractions for a given core mass for the pebble model compared to the planetesimal one caused by luminosity differences. This also implies planets with lower densities which could be confirmed observationally. Focusing on giant planets, we conclude that the sensitivity of their formation differs: for the pebble accretion model, the time at which the embryos are formed, as well as the period over which solids are accreted strongly impact the results, while for the planetesimal model it depends on the planetesimal size and on the splitting in the amount of solids available to form planetesimals.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77718711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The deep ocean (~100 km) of Europa, Jupiter’s moon, is covered by a thick (tens of km) icy shell, and is one of the most probable places in the solar sys- tem to find extraterrestrial life. Yet, its ocean dynamics and its interaction with the ice cover have so far received little attention. Previous studies sug- gested that Europa’s ocean is turbulent, yet neglected to take into account the effects of ocean salinity and appropriate boundary conditions for the ocean’s temperature. Here, the ocean dynamics of Europa is studied using global ocean models that include non-hydrostatic effects, a full Coriolis force, con- sistent top and bottom heating boundary conditions, and including the effects of melting and freezing of ice on salinity. The density is found to be dominated by salinity effects and the ocean is very weakly stratified. The ocean exhibits strong transient vertical convection, eddies, low latitude zonal jets and Tay- lor columns parallel to Europa’s axis of rotation. In the equatorial region, the Taylor columns do not intersect the ocean bottom and propagate equatorward, while off the equator, the Taylor columns are static. The meridional oceanic heat transport is intense enough to result in a nearly uniform ice thickness, that is expected to be observable in future missions.
{"title":"Europa's dynamic ocean: Taylor columns, eddies, convection, ice melting and salinity","authors":"Y. Ashkenazy, E. Tziperman","doi":"10.5194/epsc2020-538","DOIUrl":"https://doi.org/10.5194/epsc2020-538","url":null,"abstract":"<p class=\"p1\">The deep ocean (~100 km) of Europa, Jupiter’s moon, is covered by a thick (tens of km) icy shell, and is one of the most probable places in the solar sys- tem to find extraterrestrial life. Yet, its ocean dynamics and its interaction with the ice cover have so far received little attention. Previous studies sug- gested that Europa’s ocean is turbulent, yet neglected to take into account the effects of ocean salinity and appropriate boundary conditions for the ocean’s temperature. Here, the ocean dynamics of Europa is studied using global ocean models that include non-hydrostatic effects, a full Coriolis force, con- sistent top and bottom heating boundary conditions, and including the effects of melting and freezing of ice on salinity. The density is found to be dominated by salinity effects and the ocean is very weakly stratified. The ocean exhibits strong transient vertical convection, eddies, low latitude zonal jets and Tay- lor columns parallel to Europa’s axis of rotation. In the equatorial region, the Taylor columns do not intersect the ocean bottom and propagate equatorward, while off the equator, the Taylor columns are static. The meridional oceanic heat transport is intense enough to result in a nearly uniform ice thickness, that is expected to be observable in future missions.</p>","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90113920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-02DOI: 10.1016/j.icarus.2020.114268
J. Méndez Harper, J. Dufek, G. McDonald
{"title":"Detection of spark discharges in an agitated Mars dust simulant isolated from foreign surfaces","authors":"J. Méndez Harper, J. Dufek, G. McDonald","doi":"10.1016/j.icarus.2020.114268","DOIUrl":"https://doi.org/10.1016/j.icarus.2020.114268","url":null,"abstract":"","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73445735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-01DOI: 10.1051/0004-6361/202037997
Y. Moulane, E. Jehin, P. Rousselot, J. Manfroid, Y. Shinnaka, F. Pozuelos, D. Hutsem'ekers, C. Opitom, B. Yang, Z. Benkhaldoun
We report on photometry and high resolution spectroscopy of the chemically peculiar Jupiter-family Comet (hereafter JFC) 21P/Giacobini-Zinner. Comet 21P is a well known member of the carbon-chain depleted family but displays also a depletion of amines. We monitored continuously the comet over more than seven months with the two TRAPPIST telescopes (TN and TS), covering a large heliocentric distance range from 1.60 au inbound to 2.10 au outbound with a perihelion at 1.01 au on September 10, 2018. We computed and followed the evolution of the dust (represented by Af$rho$) and gas production rates of the daughter species OH, NH, CN, C$_3$, and C$_2$ and their relative abundances to OH and to CN over the comet orbit. We compared them to those measured in the previous apparitions. The activity of the comet and its water production rate reached a maximum of (3.72$pm$0.07)$times$10$^{28}$ molec/s on August 17, 2018 (r$_h$=1.07 au), 24 days before perihelion. The peak value of A(0)f$rho$ was reached on the same date (1646$pm$13) cm in the red filter. The abundance ratios of the various species are remarkably constant over a large range of heliocentric distances, before and after perihelion, showing a high level of homogeneity of the ices in the surface of the nucleus. The behaviour and level of the activity of the comet is also remarkably similar over the last five orbits. About the coma dust colour, 21P shows reflectively gradients similar to JFCs. We obtained a high resolution spectrum of 21P with UVES at ESO VLT one week after perihelion. Using the CN B-X (0,0) violet band, we measured $^{12}$C/$^{13}$C and $^{14}$N/$^{15}$N isotopic ratios of 100$pm$10 and 145$pm$10, respectively, both in very good agreement with what is usually found in comets.
{"title":"Photometry and high-resolution spectroscopy of comet 21P/Giacobini-Zinner during its 2018 apparition","authors":"Y. Moulane, E. Jehin, P. Rousselot, J. Manfroid, Y. Shinnaka, F. Pozuelos, D. Hutsem'ekers, C. Opitom, B. Yang, Z. Benkhaldoun","doi":"10.1051/0004-6361/202037997","DOIUrl":"https://doi.org/10.1051/0004-6361/202037997","url":null,"abstract":"We report on photometry and high resolution spectroscopy of the chemically peculiar Jupiter-family Comet (hereafter JFC) 21P/Giacobini-Zinner. Comet 21P is a well known member of the carbon-chain depleted family but displays also a depletion of amines. We monitored continuously the comet over more than seven months with the two TRAPPIST telescopes (TN and TS), covering a large heliocentric distance range from 1.60 au inbound to 2.10 au outbound with a perihelion at 1.01 au on September 10, 2018. We computed and followed the evolution of the dust (represented by Af$rho$) and gas production rates of the daughter species OH, NH, CN, C$_3$, and C$_2$ and their relative abundances to OH and to CN over the comet orbit. We compared them to those measured in the previous apparitions. The activity of the comet and its water production rate reached a maximum of (3.72$pm$0.07)$times$10$^{28}$ molec/s on August 17, 2018 (r$_h$=1.07 au), 24 days before perihelion. The peak value of A(0)f$rho$ was reached on the same date (1646$pm$13) cm in the red filter. The abundance ratios of the various species are remarkably constant over a large range of heliocentric distances, before and after perihelion, showing a high level of homogeneity of the ices in the surface of the nucleus. The behaviour and level of the activity of the comet is also remarkably similar over the last five orbits. About the coma dust colour, 21P shows reflectively gradients similar to JFCs. We obtained a high resolution spectrum of 21P with UVES at ESO VLT one week after perihelion. Using the CN B-X (0,0) violet band, we measured $^{12}$C/$^{13}$C and $^{14}$N/$^{15}$N isotopic ratios of 100$pm$10 and 145$pm$10, respectively, both in very good agreement with what is usually found in comets.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87006023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-01DOI: 10.1051/0004-6361/201936916
A. Michel, J. Haldemann, C. Mordasini, Y. Alibert
Planet formation theory suggests that planet bulk compositions are likely to reflect the chemical abundance ratios of their host star's photosphere. Variations in the abundance of particular chemical species in stellar photospheres between different galactic stellar populations demonstrate that there are differences among the expected solid planet bulk compositions. We aim to present planetary mass-radius relations of solid planets for kinematically differentiated stellar populations, namely, the thin disc, thick disc, and halo. Using two separate internal structure models, we generated synthetic planets using bulk composition inputs derived from stellar abundances. We explored two scenarios, specifically iron-silicate planets at 0.1 AU and silicate-iron-water planets at 4 AU. We show that there is a persistent statistical difference in the expected mass-radius relations of solid planets among the different galactic stellar populations. At 0.1 AU for silicate-iron planets, there is a 1.51 to 2.04% mean planetary radius difference between the thick and thin disc stellar populations, whilst for silicate-iron-water planets past the ice line at 4 AU, we calculate a 2.93 to 3.26% difference depending on the models. Between the halo and thick disc, we retrieve at 0.1 AU a 0.53 to 0.69% mean planetary radius difference, and at 4 AU we find a 1.24 to 1.49% difference depending on the model. Future telescopes (such as PLATO) will be able to precisely characterize solid exoplanets and demonstrate the possible existence of planetary mass-radius relationship variability between galactic stellar populations.
{"title":"Planetary mass–radius relations across the galaxy","authors":"A. Michel, J. Haldemann, C. Mordasini, Y. Alibert","doi":"10.1051/0004-6361/201936916","DOIUrl":"https://doi.org/10.1051/0004-6361/201936916","url":null,"abstract":"Planet formation theory suggests that planet bulk compositions are likely to reflect the chemical abundance ratios of their host star's photosphere. Variations in the abundance of particular chemical species in stellar photospheres between different galactic stellar populations demonstrate that there are differences among the expected solid planet bulk compositions. We aim to present planetary mass-radius relations of solid planets for kinematically differentiated stellar populations, namely, the thin disc, thick disc, and halo. Using two separate internal structure models, we generated synthetic planets using bulk composition inputs derived from stellar abundances. We explored two scenarios, specifically iron-silicate planets at 0.1 AU and silicate-iron-water planets at 4 AU. We show that there is a persistent statistical difference in the expected mass-radius relations of solid planets among the different galactic stellar populations. At 0.1 AU for silicate-iron planets, there is a 1.51 to 2.04% mean planetary radius difference between the thick and thin disc stellar populations, whilst for silicate-iron-water planets past the ice line at 4 AU, we calculate a 2.93 to 3.26% difference depending on the models. Between the halo and thick disc, we retrieve at 0.1 AU a 0.53 to 0.69% mean planetary radius difference, and at 4 AU we find a 1.24 to 1.49% difference depending on the model. Future telescopes (such as PLATO) will be able to precisely characterize solid exoplanets and demonstrate the possible existence of planetary mass-radius relationship variability between galactic stellar populations.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88092569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-01DOI: 10.1051/0004-6361/201936672
Daohai Li, A. Johansen, A. Mustill, M. Davies, A. Christou
Single-binary scattering may lead to an exchange where the single object captures a component of the binary, forming a new binary. This has been well studied in encounters between a star--planet pair and a single star. Here we explore the application of the exchange mechanism to a planet--satellite pair and another planet in the gravitational potential of a central star. As a case study, we focus on encounters between a satellite-bearing object and Neptune. We investigate whether Neptune can capture satellites from that object and if the captured satellites have orbits analogous to the Neptunian moons Triton and Nereid. Using $N$-body simulations, we study the capture probability at different encounter distances. Post-capture, we use a simple analytical argument to estimate how the captured orbits evolve under collisional and tidal effects. We find that the average capture probability reaches $sim$$10%$ if Neptune penetrates the donor planet's satellite system. Most moons grabbed by Neptune acquire highly eccentric orbits. Post-capture, around half of those captured, especially those on tight orbits, can be circularised, either by tides only or by collisions+tides, turning into Triton-like objects. Captures further out, on the other hand, stay on wide and eccentric orbits like that of Nereid. Both moon types can be captured in the same encounter and they have wide distributions in orbital inclination. Therefore, Triton naturally has a $sim$50% chance of being retrograde. A similar process potentially applies to an exoplanetary system, and our model predicts that exomoons can jump from one planet to another during planetary scattering. Specifically, there should be two distinct populations of captured moons: one on close-in circular orbits and the other on far-out eccentric orbits. The two populations may have highly inclined prograde or retrograde orbits.
{"title":"Capture of satellites during planetary encounters","authors":"Daohai Li, A. Johansen, A. Mustill, M. Davies, A. Christou","doi":"10.1051/0004-6361/201936672","DOIUrl":"https://doi.org/10.1051/0004-6361/201936672","url":null,"abstract":"Single-binary scattering may lead to an exchange where the single object captures a component of the binary, forming a new binary. This has been well studied in encounters between a star--planet pair and a single star. Here we explore the application of the exchange mechanism to a planet--satellite pair and another planet in the gravitational potential of a central star. As a case study, we focus on encounters between a satellite-bearing object and Neptune. We investigate whether Neptune can capture satellites from that object and if the captured satellites have orbits analogous to the Neptunian moons Triton and Nereid. Using $N$-body simulations, we study the capture probability at different encounter distances. Post-capture, we use a simple analytical argument to estimate how the captured orbits evolve under collisional and tidal effects. We find that the average capture probability reaches $sim$$10%$ if Neptune penetrates the donor planet's satellite system. Most moons grabbed by Neptune acquire highly eccentric orbits. Post-capture, around half of those captured, especially those on tight orbits, can be circularised, either by tides only or by collisions+tides, turning into Triton-like objects. Captures further out, on the other hand, stay on wide and eccentric orbits like that of Nereid. Both moon types can be captured in the same encounter and they have wide distributions in orbital inclination. Therefore, Triton naturally has a $sim$50% chance of being retrograde. A similar process potentially applies to an exoplanetary system, and our model predicts that exomoons can jump from one planet to another during planetary scattering. Specifically, there should be two distinct populations of captured moons: one on close-in circular orbits and the other on far-out eccentric orbits. The two populations may have highly inclined prograde or retrograde orbits.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85950132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
'A. Kereszturi, J. Aszal'os, Zs. Heiling, Zs. Kapui, Cs. Kir'aly, Sz. Leel-Ossy, B. Nagy, Zs. Nemerk'enyi, B. P'al, 'A. Skult'eti, Z. Szalai
The Special Collection of papers in this issue of Astrobiology provide an overview of the characteristics and potential for future exploration of the Ojos del Salado volcano, located in the Andes Mountains in front of the Atacama Desert in northern Chile. The main benefits of this site compared with others are the combination of strong UV radiation, the presence of permafrost, and geothermal activity within a dry terrain. The interaction between limited snow events and wind results in snow patches buried under a dry soil surface. This leads to ephemeral water streams that only flow duringdaytime hours. On this volcano, which has the highest located subsurface temperature monitoring systems reported to date, seasonal melting of the permafrost is followed by fast percolation events. This is due to the high porosity of these soils. The results are landforms that shaped by the strong winds. At this site, both thermal springs and lakes (the latter arising from melting ice) provide habitats for life; a 6480m high lake heated by volcanic activity shows both warm and cold sediments that contain a number of different microbial species, including psychrophiles. Where the permafrost melts, thawing ponds have formed at 5900m that is dominated by populations of Bacteroidetes and Proteobacteria, while in the pond sediments and the permafrost itself Acidobacteria, Actinobacteria, Bacteroidetes, Patescibacteria, Proteobacteria, and Verrucomicrobia are abundant. In turn, fumaroles show the presence of acidophilic iron-oxidizers and iron-reducing species. In spite of the extreme conditions reported at Ojos del Salado, this site is easily accessible.
本期《天体生物学》的论文特辑概述了位于智利北部阿塔卡马沙漠前安第斯山脉的Ojos del Salado火山的特征和未来探索的潜力。与其他地点相比，这个地点的主要优点是强紫外线辐射、永久冻土的存在和干燥地形中的地热活动的结合。有限的降雪事件和风的相互作用导致积雪埋在干燥的土壤表面下。这导致了短暂的水流，只在白天流动。在这座火山上，有迄今为止报告的最高的地下温度监测系统，永久冻土的季节性融化之后是快速渗透事件。这是由于这些土壤的高孔隙率。结果形成了由强风塑造的地貌。在这个地方，温泉和湖泊(后者来自融化的冰)都为生命提供了栖息地;一个由火山活动加热的6480米高的湖泊显示出温暖和寒冷的沉积物，其中包含许多不同的微生物物种，包括嗜冷微生物。在永久冻土层融化的地方，在5900米处形成了以拟杆菌门和变形杆菌门为主的融化池塘，而在池塘沉积物和永久冻土层中，酸杆菌门、放线菌门、拟杆菌门、Patescibacteria、变形杆菌门和Verrucomicrobia丰富。反过来，喷气孔显示了亲酸性铁氧化剂和铁还原物质的存在。尽管在Ojos del Salado报道了极端的条件，但这个地点很容易到达。
{"title":"Cold, Dry, Windy, and UV Irradiated: Surveying Mars-Relevant Conditions in Ojos del Salado Volcano (Andes Mountains, Chile)","authors":"'A. Kereszturi, J. Aszal'os, Zs. Heiling, Zs. Kapui, Cs. Kir'aly, Sz. Leel-Ossy, B. Nagy, Zs. Nemerk'enyi, B. P'al, 'A. Skult'eti, Z. Szalai","doi":"10.1089/ast.2019.2165","DOIUrl":"https://doi.org/10.1089/ast.2019.2165","url":null,"abstract":"The Special Collection of papers in this issue of Astrobiology provide an overview of the characteristics and potential for future exploration of the Ojos del Salado volcano, located in the Andes Mountains in front of the Atacama Desert in northern Chile. The main benefits of this site compared with others are the combination of strong UV radiation, the presence of permafrost, and geothermal activity within a dry terrain. The interaction between limited snow events and wind results in snow patches buried under a dry soil surface. This leads to ephemeral water streams that only flow duringdaytime hours. On this volcano, which has the highest located subsurface temperature monitoring systems reported to date, seasonal melting of the permafrost is followed by fast percolation events. This is due to the high porosity of these soils. The results are landforms that shaped by the strong winds. At this site, both thermal springs and lakes (the latter arising from melting ice) provide habitats for life; a 6480m high lake heated by volcanic activity shows both warm and cold sediments that contain a number of different microbial species, including psychrophiles. Where the permafrost melts, thawing ponds have formed at 5900m that is dominated by populations of Bacteroidetes and Proteobacteria, while in the pond sediments and the permafrost itself Acidobacteria, Actinobacteria, Bacteroidetes, Patescibacteria, Proteobacteria, and Verrucomicrobia are abundant. In turn, fumaroles show the presence of acidophilic iron-oxidizers and iron-reducing species. In spite of the extreme conditions reported at Ojos del Salado, this site is easily accessible.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74941439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-05-20DOI: 10.1051/0004-6361/202037984
A. Maire, K. Molaverdikhani, S. Desidera, T. Trifonov, P. Mollière, V. D’Orazi, N. Frankel, J. Baudino, S. Messina, A. Muller, B. Charnay, A. Cheetham, P. Delorme, R. Ligi, M. Bonnefoy, W. Brandner, D. Mesa, F. Cantalloube, R. Galicher, T. Henning, B. Biller, J. Hagelberg, A. Lagrange, B. Lavie, E. Rickman, D. S'egransan, S. Udry, G. Chauvin, R. Gratton, M. Langlois, A. Vigan, M. Meyer, J. Beuzit, T. Bhowmik, A. Boccaletti, C. Lazzoni, C. Perrot, T. Schmidt, A. Zurlo, L. Gluck, J. Pragt, J. Ramos, R. Roelfsema, A. Roux, J. Sauvage
Context. Detecting and characterizing substellar companions for which the luminosity, mass, and age can be determined independently is of utter importance to test and calibrate the evolutionary models due to uncertainties in their formation mechanisms. HD 19467 is a bright and nearby star hosting a cool brown dwarf companion detected with RV and imaging, making it a valuable object for such studies. Aims. We aim to further characterize the orbital, spectral, and physical properties of the HD 19467 system. Methods. We present new high-contrast imaging data with the SPHERE and NaCo instruments. We also analyze archival data from HARPS, NaCo, HIRES, UVES, and ASAS. We also use proper motion data of the star from Hipparcos and Gaia. Results. We refine the properties of the host star and derive an age of 8.0$^{+2.0}_{-1.0}$ Gyr based on isochrones, gyrochronology, and chemical and kinematic arguments. This estimate is slightly younger than previous estimates of ~9-11 Gyr. No orbital curvature is seen in the current imaging, RV, and astrometric data. From a joint fit of the data, we refine the orbital parameters for HD 19467B: period 398$^{+95}_{-93}$ yr, inclination 129.8$^{+8.1}_{-5.1}$ deg, eccentricity 0.56$pm$0.09, longitude of the ascending node 134.8$pm$4.5 deg, and argument of the periastron 64.2$^{+5.5}_{-6.3}$ deg. We assess a dynamical mass of 74$^{+12}_{-9}$ MJ. The fit with atmospheric models of the spectrophotometric data of HD 19467B indicates an atmosphere without clouds or with very thin clouds, an effective temperature of 1042$^{+77}_{-71}$ K, and a large surface gravity of 5.34$^{+0.08}_{-0.09}$ dex. The comparison to model predictions of the bolometric luminosity and dynamical mass of HD 19467B, assuming our system age estimate, indicates a better agreement with the Burrows et al. models; whereas the other evolutionary models used tend to underestimate its cooling rate.
{"title":"Orbital and spectral characterization of the benchmark T-type brown dwarf HD 19467B","authors":"A. Maire, K. Molaverdikhani, S. Desidera, T. Trifonov, P. Mollière, V. D’Orazi, N. Frankel, J. Baudino, S. Messina, A. Muller, B. Charnay, A. Cheetham, P. Delorme, R. Ligi, M. Bonnefoy, W. Brandner, D. Mesa, F. Cantalloube, R. Galicher, T. Henning, B. Biller, J. Hagelberg, A. Lagrange, B. Lavie, E. Rickman, D. S'egransan, S. Udry, G. Chauvin, R. Gratton, M. Langlois, A. Vigan, M. Meyer, J. Beuzit, T. Bhowmik, A. Boccaletti, C. Lazzoni, C. Perrot, T. Schmidt, A. Zurlo, L. Gluck, J. Pragt, J. Ramos, R. Roelfsema, A. Roux, J. Sauvage","doi":"10.1051/0004-6361/202037984","DOIUrl":"https://doi.org/10.1051/0004-6361/202037984","url":null,"abstract":"Context. Detecting and characterizing substellar companions for which the luminosity, mass, and age can be determined independently is of utter importance to test and calibrate the evolutionary models due to uncertainties in their formation mechanisms. HD 19467 is a bright and nearby star hosting a cool brown dwarf companion detected with RV and imaging, making it a valuable object for such studies. Aims. We aim to further characterize the orbital, spectral, and physical properties of the HD 19467 system. Methods. We present new high-contrast imaging data with the SPHERE and NaCo instruments. We also analyze archival data from HARPS, NaCo, HIRES, UVES, and ASAS. We also use proper motion data of the star from Hipparcos and Gaia. Results. We refine the properties of the host star and derive an age of 8.0$^{+2.0}_{-1.0}$ Gyr based on isochrones, gyrochronology, and chemical and kinematic arguments. This estimate is slightly younger than previous estimates of ~9-11 Gyr. No orbital curvature is seen in the current imaging, RV, and astrometric data. From a joint fit of the data, we refine the orbital parameters for HD 19467B: period 398$^{+95}_{-93}$ yr, inclination 129.8$^{+8.1}_{-5.1}$ deg, eccentricity 0.56$pm$0.09, longitude of the ascending node 134.8$pm$4.5 deg, and argument of the periastron 64.2$^{+5.5}_{-6.3}$ deg. We assess a dynamical mass of 74$^{+12}_{-9}$ MJ. The fit with atmospheric models of the spectrophotometric data of HD 19467B indicates an atmosphere without clouds or with very thin clouds, an effective temperature of 1042$^{+77}_{-71}$ K, and a large surface gravity of 5.34$^{+0.08}_{-0.09}$ dex. The comparison to model predictions of the bolometric luminosity and dynamical mass of HD 19467B, assuming our system age estimate, indicates a better agreement with the Burrows et al. models; whereas the other evolutionary models used tend to underestimate its cooling rate.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"86 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89041335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-05-06DOI: 10.1051/0004-6361/202038027
S. Facchini, M. Benisty, J. Bae, R. Loomis, L. M. Pérez, M. Ansdell, S. Mayama, Paola Pinilla, Richard Teague, A. Isella, A. Mann
We present high resolution millimeter continuum ALMA observations of the disks around the T Tauri stars LkCa 15 and J1610. These disks host dust-depleted inner regions, possibly carved by massive planets, and are of prime interest to study the imprints of planet-disk interactions. While at moderate angular resolution they appear as a broad ring surrounding a cavity, the continuum emission resolves into multiple rings at a resolution of ~60$times$40 mas (~7.5 au for LkCa 15, ~6 au for J1610) and ~$7,mu$Jy beam$^{-1}$ rms at 1.3 mm. In addition to a broad extended component, LkCa 15 and J1610 host 3 and 2 narrow rings, respectively, with two bright rings in LkCa 15 being radially resolved. The rings look marginally optically thick, with peak optical depths of ~0.5 (neglecting scattering), in agreement with high angular resolution observations of full disks. We perform hydrodynamical simulations with an embedded, sub-Jovian-mass planet and show that the observed multi-ringed substructure can be qualitatively explained as the outcome of the planet-disk interaction. We note however that the choice of the disk cooling timescale alone can significantly impact the resulting gas and dust distributions around the planet, leading to different numbers of rings and gaps and different spacings between them. We propose that the massive outer disk regions of transition disks are favorable places for planetesimals and possibly second generation planet formation of objects with a lower mass than the planets carving the inner cavity (typically few $M_{rm Jup}$), and that the annular substructures observed in LkCa 15 and J1610 may be indicative of planetary core formation within dust-rich pressure traps. Current observations are compatible with other mechanisms being at the origin of the observed substructures, in particular with narrow rings generated at the edge of the CO and N$_2$ snowlines.
{"title":"Annular substructures in the transition disks around LkCa 15 and J1610","authors":"S. Facchini, M. Benisty, J. Bae, R. Loomis, L. M. Pérez, M. Ansdell, S. Mayama, Paola Pinilla, Richard Teague, A. Isella, A. Mann","doi":"10.1051/0004-6361/202038027","DOIUrl":"https://doi.org/10.1051/0004-6361/202038027","url":null,"abstract":"We present high resolution millimeter continuum ALMA observations of the disks around the T Tauri stars LkCa 15 and J1610. These disks host dust-depleted inner regions, possibly carved by massive planets, and are of prime interest to study the imprints of planet-disk interactions. While at moderate angular resolution they appear as a broad ring surrounding a cavity, the continuum emission resolves into multiple rings at a resolution of ~60$times$40 mas (~7.5 au for LkCa 15, ~6 au for J1610) and ~$7,mu$Jy beam$^{-1}$ rms at 1.3 mm. In addition to a broad extended component, LkCa 15 and J1610 host 3 and 2 narrow rings, respectively, with two bright rings in LkCa 15 being radially resolved. The rings look marginally optically thick, with peak optical depths of ~0.5 (neglecting scattering), in agreement with high angular resolution observations of full disks. We perform hydrodynamical simulations with an embedded, sub-Jovian-mass planet and show that the observed multi-ringed substructure can be qualitatively explained as the outcome of the planet-disk interaction. We note however that the choice of the disk cooling timescale alone can significantly impact the resulting gas and dust distributions around the planet, leading to different numbers of rings and gaps and different spacings between them. We propose that the massive outer disk regions of transition disks are favorable places for planetesimals and possibly second generation planet formation of objects with a lower mass than the planets carving the inner cavity (typically few $M_{rm Jup}$), and that the annular substructures observed in LkCa 15 and J1610 may be indicative of planetary core formation within dust-rich pressure traps. Current observations are compatible with other mechanisms being at the origin of the observed substructures, in particular with narrow rings generated at the edge of the CO and N$_2$ snowlines.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74381726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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