Pub Date : 2020-07-20DOI: 10.1051/0004-6361/202038280
D. Modirrousta-Galian, B. Stelzer, E. Magaudda, J. Maldonado, M. Gudel, J. Sanz-Forcada, B. Edwards, G. Micela
In this paper we present a deep X-ray observation of the nearby M dwarf GJ 357 and use it to put constraints on the atmospheric evolution of its planet, GJ 357 b. We also analyse the systematic errors in the stellar parameters of GJ 357 in order to see how they affect the perceived planetary properties. We estimate the age of GJ 357 b by comparing the observed X-ray luminosity of its host star, derived from a recent {em XMM-Newton} observation {($log{L_{rm x}},{rm [erg/s]} = 25.73$), with $L_{rm x} -$ age relations for M dwarfs. We find that GJ 357 presents one of the lowest X-ray activity levels ever measured for an M dwarf, and we put a lower limit on its age of $5$,Gyr.} Using this age limit, we perform a backwards reconstruction of the original primordial atmospheric reservoir. Furthermore, by considering the systematic errors in the stellar parameters, we find a range of possible planetary masses, radii, and densities. From the backwards reconstruction of GJ 357 b's irradiation history we find that the upper limit of its initial primordial atmospheric mass is $sim rm 38M_{oplus}$. An initial atmospheric reservoir significantly larger than this may have survived through the X-ray and ultraviolet irradiation history, hence being inconsistent with current observations that suggest a telluric composition. In spite of the unlikelihood of a currently existing primordial envelope, volcanism and outgassing may have contributed to a secondary atmosphere. Under this assumption, we present three different synthetic infrared spectra for GJ 357 b that one might expect, consisting of $100%~rm CO_{2}$, $100%~rm SO_{2}$, and $75%~ rm N_{2}$, $24%~rm CO_{2}$ and $1%~rm H_{2}O$.
{"title":"GJ 357 b","authors":"D. Modirrousta-Galian, B. Stelzer, E. Magaudda, J. Maldonado, M. Gudel, J. Sanz-Forcada, B. Edwards, G. Micela","doi":"10.1051/0004-6361/202038280","DOIUrl":"https://doi.org/10.1051/0004-6361/202038280","url":null,"abstract":"In this paper we present a deep X-ray observation of the nearby M dwarf GJ 357 and use it to put constraints on the atmospheric evolution of its planet, GJ 357 b. We also analyse the systematic errors in the stellar parameters of GJ 357 in order to see how they affect the perceived planetary properties. We estimate the age of GJ 357 b by comparing the observed X-ray luminosity of its host star, derived from a recent {em XMM-Newton} observation {($log{L_{rm x}},{rm [erg/s]} = 25.73$), with $L_{rm x} -$ age relations for M dwarfs. We find that GJ 357 presents one of the lowest X-ray activity levels ever measured for an M dwarf, and we put a lower limit on its age of $5$,Gyr.} Using this age limit, we perform a backwards reconstruction of the original primordial atmospheric reservoir. Furthermore, by considering the systematic errors in the stellar parameters, we find a range of possible planetary masses, radii, and densities. From the backwards reconstruction of GJ 357 b's irradiation history we find that the upper limit of its initial primordial atmospheric mass is $sim rm 38M_{oplus}$. An initial atmospheric reservoir significantly larger than this may have survived through the X-ray and ultraviolet irradiation history, hence being inconsistent with current observations that suggest a telluric composition. In spite of the unlikelihood of a currently existing primordial envelope, volcanism and outgassing may have contributed to a secondary atmosphere. Under this assumption, we present three different synthetic infrared spectra for GJ 357 b that one might expect, consisting of $100%~rm CO_{2}$, $100%~rm SO_{2}$, and $75%~ rm N_{2}$, $24%~rm CO_{2}$ and $1%~rm H_{2}O$.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88842910","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 : 2020-07-10DOI: 10.1051/0004-6361/202038188
B. Benmahi, T. Cavali'e, M. Dobrijevic, N. Biver, K. Bermudez-Diaz, A. Sandqvist, E. Lellouch, R. Moreno, T. Fouchet, V. Hue, P. Hartogh, F. Billebaud, A. Lecacheux, A. Hjalmarson, U. Frisk, M. Olberg
Comet Shoemaker-Levy 9 impacted Jupiter in July 1994, leaving its stratosphere with several new species, among them water vapor (H2O). With the aid of a photochemical model H2O can be used as a dynamical tracer in the jovian stratosphere. In this paper, we aim at constraining vertical eddy diffusion (Kzz) at the levels where H2O resides. We monitored the H2O disk-averaged emission at 556.936 GHz with the Odin space telescope between 2002 and 2019, covering nearly two decades. We analyzed the data with a combination of 1D photochemical and radiative transfer models to constrain vertical eddy diffusion in the stratosphere of Jupiter. The Odin observations show us that the emission of H2O has an almost linear decrease of about 40% between 2002 and 2019.We can only reproduce our time series if we increase the magnitude of Kzz in the pressure range where H2O diffuses downward from 2002 to 2019, i.e. from ~0.2 mbar to ~5 mbar. However, this modified Kzz is incompatible with hydrocarbon observations. We find that, even if allowance is made for the initially large abundances of H2O and CO at the impact latitudes, the photochemical conversion of H2O to CO2 is not sufficient to explain the progressive decline of the H2O line emission, suggestive of additional loss mechanisms. The Kzz we derived from the Odin observations of H2O can only be viewed as an upper limit in the ~0.2 mbar to ~5 mbar pressure range. The incompatibility between the interpretations made from H2O and hydrocarbon observations probably results from 1D modeling limitations. Meridional variability of H2O, most probably at auroral latitudes, would need to be assessed and compared with that of hydrocarbons to quantify the role of auroral chemistry in the temporal evolution of the H2O abundance since the SL9 impacts. Modeling the temporal evolution of SL9 species with a 2D model would be the next natural step.
{"title":"Monitoring of the evolution of H2O vapor in the stratosphere of Jupiter over an 18-yr period with the Odin space telescope","authors":"B. Benmahi, T. Cavali'e, M. Dobrijevic, N. Biver, K. Bermudez-Diaz, A. Sandqvist, E. Lellouch, R. Moreno, T. Fouchet, V. Hue, P. Hartogh, F. Billebaud, A. Lecacheux, A. Hjalmarson, U. Frisk, M. Olberg","doi":"10.1051/0004-6361/202038188","DOIUrl":"https://doi.org/10.1051/0004-6361/202038188","url":null,"abstract":"Comet Shoemaker-Levy 9 impacted Jupiter in July 1994, leaving its stratosphere with several new species, among them water vapor (H2O). With the aid of a photochemical model H2O can be used as a dynamical tracer in the jovian stratosphere. In this paper, we aim at constraining vertical eddy diffusion (Kzz) at the levels where H2O resides. We monitored the H2O disk-averaged emission at 556.936 GHz with the Odin space telescope between 2002 and 2019, covering nearly two decades. We analyzed the data with a combination of 1D photochemical and radiative transfer models to constrain vertical eddy diffusion in the stratosphere of Jupiter. The Odin observations show us that the emission of H2O has an almost linear decrease of about 40% between 2002 and 2019.We can only reproduce our time series if we increase the magnitude of Kzz in the pressure range where H2O diffuses downward from 2002 to 2019, i.e. from ~0.2 mbar to ~5 mbar. However, this modified Kzz is incompatible with hydrocarbon observations. We find that, even if allowance is made for the initially large abundances of H2O and CO at the impact latitudes, the photochemical conversion of H2O to CO2 is not sufficient to explain the progressive decline of the H2O line emission, suggestive of additional loss mechanisms. The Kzz we derived from the Odin observations of H2O can only be viewed as an upper limit in the ~0.2 mbar to ~5 mbar pressure range. The incompatibility between the interpretations made from H2O and hydrocarbon observations probably results from 1D modeling limitations. Meridional variability of H2O, most probably at auroral latitudes, would need to be assessed and compared with that of hydrocarbons to quantify the role of auroral chemistry in the temporal evolution of the H2O abundance since the SL9 impacts. Modeling the temporal evolution of SL9 species with a 2D model would be the next natural step.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"452 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86860672","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}
R. Heller, J. Duda, M. Winkler, J. Reitner, L. Gizon
Geological evidence suggests liquid water near the Earth's surface as early as 4.4 gigayears ago when the faint young Sun only radiated about 70 % of its modern power output. At this point, the Earth should have been a global snowball. An extreme atmospheric greenhouse effect, an initially more massive Sun, release of heat acquired during the accretion process of protoplanetary material, and radioactivity of the early Earth material have been proposed as alternative reservoirs or traps for heat. For now, the faint-young-sun paradox persists as one of the most important unsolved problems in our understanding of the origin of life on Earth. Here we use astrophysical models to explore the possibility that the new-born Moon, which formed about 69 million years (Myr) after the ignition of the Sun, generated extreme tidal friction - and therefore heat - in the Hadean and possibly the Archean Earth. We show that the Earth-Moon system has lost about 3e31 J, (99 % of its initial mechanical energy budget) as tidal heat. Tidal heating of roughly 10 W/m^2 through the surface on a time scale of 100 Myr could have accounted for a temperature increase of up to 5 degrees Celsius on the early Earth. This heating effect alone does not solve the faint-young-sun paradox but it could have played a key role in combination with other effects. Future studies of the interplay of tidal heating, the evolution of the solar power output, and the atmospheric (greenhouse) effects on the early Earth could help in solving the faint-young-sun paradox.
{"title":"Habitability of the early Earth: Liquid water under a faint young Sun facilitated by strong tidal heating due to a nearby Moon","authors":"R. Heller, J. Duda, M. Winkler, J. Reitner, L. Gizon","doi":"10.31223/osf.io/9nrwh","DOIUrl":"https://doi.org/10.31223/osf.io/9nrwh","url":null,"abstract":"Geological evidence suggests liquid water near the Earth's surface as early as 4.4 gigayears ago when the faint young Sun only radiated about 70 % of its modern power output. At this point, the Earth should have been a global snowball. An extreme atmospheric greenhouse effect, an initially more massive Sun, release of heat acquired during the accretion process of protoplanetary material, and radioactivity of the early Earth material have been proposed as alternative reservoirs or traps for heat. For now, the faint-young-sun paradox persists as one of the most important unsolved problems in our understanding of the origin of life on Earth. Here we use astrophysical models to explore the possibility that the new-born Moon, which formed about 69 million years (Myr) after the ignition of the Sun, generated extreme tidal friction - and therefore heat - in the Hadean and possibly the Archean Earth. We show that the Earth-Moon system has lost about 3e31 J, (99 % of its initial mechanical energy budget) as tidal heat. Tidal heating of roughly 10 W/m^2 through the surface on a time scale of 100 Myr could have accounted for a temperature increase of up to 5 degrees Celsius on the early Earth. This heating effect alone does not solve the faint-young-sun paradox but it could have played a key role in combination with other effects. Future studies of the interplay of tidal heating, the evolution of the solar power output, and the atmospheric (greenhouse) effects on the early Earth could help in solving the faint-young-sun paradox.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80341895","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 : 2020-07-02DOI: 10.1051/0004-6361/202038187
B. Toledo-Padr'on, C. Lovis, A. Mascareno, S. Barros, J. Hern'andez, A. Sozzetti, F. Bouchy, M. Z. Osorio, R. Rebolo, S. Cristiani, F. Pepe, N. Santos, S. Sousa, H. Tabernero, J. Lillo-Box, D. Bossini, V. Adibekyan, R. Allart, M. Damasso, V. D’Odorico, P. Figueira, B. Lavie, G. Curto, A. Mehner, G. Micela, A. Modigliani, N. Nunes, E. Pall'e, M. Abreu, M. Affolter, Y. Alibert, M. Aliverti, C. Prieto, D. Alves, M. Amate, G. Ávila, V. Baldini, T. Bandy, S. Benatti, W. Benz, A. Bianco, C. Broeg, A. Cabral, G. Calderone, R. Cirami, J. Coelho, P. Conconi, I. Coretti, C. Cumani, G. Cupani, S. Deiries, H. Dekker, B. Delabre, O. Demangeon, P. D. Marcantonio, D. Ehrenreich, A. Fragoso, L. Genolet, M. Genoni, R. G. Santos, I. Hughes, O. Iwert, J. Knudstrup, M. Landoni, J. Lizon, C. Maire, A. Manescau, C. Martins, D. M'egevand, P. Molaro, M. Monteiro, M. Monteiro, M. Moschetti, E. Mueller, L. Oggioni, A. Oliveira, M. Oshagh, G. Pariani, L. Pasquini, E. Poretti, J. L. Rasilla, E. Redaelli, M. Riva, S. Tschudi, P. Sant
We characterized the transiting planetary system orbiting the G2V star K2-38 using the new-generation echelle spectrograph ESPRESSO. We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets. Using 43 ESPRESSO high-precision radial velocity measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a MCMC analysis, significantly improving their mass measurements. Using ESPRESSO spectra, we derived the stellar parameters, $T_{rm eff}$=5731$pm$66, $log g$=4.38$pm$0.11~dex, and $[Fe/H]$=0.26$pm$0.05~dex, and thus the mass and radius of K2-38, $M_{star}$=1.03 $^{+0.04}_{-0.02}$~M$_{oplus}$ and $R_{star}$=1.06 $^{+0.09}_{-0.06}$~R$_{oplus}$. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with $R_{rm P}$=1.54$pm$0.14~R$_{rm oplus}$ and $M_{rm p}$=7.3$^{+1.1}_{-1.0}$~M$_{oplus}$, and K2-38c as a sub-Neptune with $R_{rm P}$=2.29$pm$0.26~R$_{rm oplus}$ and $M_{rm p}$=8.3$^{+1.3}_{-1.3}$~M$_{oplus}$. We derived a mean density of $rho_{rm p}$=11.0$^{+4.1}_{-2.8}$~g cm$^{-3}$ for K2-38b and $rho_{rm p}$=3.8$^{+1.8}_{-1.1}$~g~cm$^{-3}$ for K2-38c, confirming K2-38b as one of the densest planets known to date. The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky model with a H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the radial velocity time-series whose origin could be linked to a 0.25-3~M$_{rm J}$ planet or stellar activity.
我们利用新一代的ESPRESSO光谱仪对G2V恒星K2-38的凌日行星系进行了表征。我们对这颗恒星的K2光度曲线进行了光度分析，以测量其两颗已知行星的半径。利用在8个月的时间里进行的43次ESPRESSO高精度径向速度测量，以及之前发表的14次HIRES RV测量，我们通过MCMC分析模拟了这两颗行星的轨道，显著改善了它们的质量测量。利用ESPRESSO光谱，我们推导出了K2-38的恒星参数$T_{rm eff}$ =5731 $pm$ 66, $log g$ =4.38 $pm$ 0.11 index, $[Fe/H]$ =0.26 $pm$ 0.05 index，从而得到了K2-38的质量和半径$M_{star}$ =1.03 $^{+0.04}_{-0.02}$ M $_{oplus}$和$R_{star}$ =1.06 $^{+0.09}_{-0.06}$ R $_{oplus}$。我们确定了两颗行星的行星属性的新值。我们认为K2-38b是一个超级地球，$R_{rm P}$ =1.54 $pm$ 0.14 R $_{rm oplus}$和$M_{rm p}$ =7.3 $^{+1.1}_{-1.0}$ M $_{oplus}$, K2-38c是一个亚海王星，$R_{rm P}$ =2.29 $pm$ 0.26 R $_{rm oplus}$和$M_{rm p}$ =8.3 $^{+1.3}_{-1.3}$ M $_{oplus}$。我们得出K2-38b的平均密度为$rho_{rm p}$ =11.0 $^{+4.1}_{-2.8}$ g cm $^{-3}$, K2-38c的平均密度为$rho_{rm p}$ =3.8 $^{+1.8}_{-1.1}$ g cm $^{-3}$，证实了K2-38b是迄今为止已知密度最大的行星之一。对K2-38b的组成最好的描述来自一个富含铁的类水星模型，而K2-38c则更适合用一个带有H2包层的岩石模型来描述。最大碰撞剥离边界显示了巨大的撞击可能是K2-38b高密度的原因。每颗行星受到的辐射使它们位于半径谷的两侧。我们在径向速度时间序列中发现了一个长周期信号的证据，其起源可能与0.25-3 M $_{rm J}$行星或恒星活动有关。
{"title":"Characterization of the K2-38 planetary system","authors":"B. Toledo-Padr'on, C. Lovis, A. Mascareno, S. Barros, J. Hern'andez, A. Sozzetti, F. Bouchy, M. Z. Osorio, R. Rebolo, S. Cristiani, F. Pepe, N. Santos, S. Sousa, H. Tabernero, J. Lillo-Box, D. Bossini, V. Adibekyan, R. Allart, M. Damasso, V. D’Odorico, P. Figueira, B. Lavie, G. Curto, A. Mehner, G. Micela, A. Modigliani, N. Nunes, E. Pall'e, M. Abreu, M. Affolter, Y. Alibert, M. Aliverti, C. Prieto, D. Alves, M. Amate, G. Ávila, V. Baldini, T. Bandy, S. Benatti, W. Benz, A. Bianco, C. Broeg, A. Cabral, G. Calderone, R. Cirami, J. Coelho, P. Conconi, I. Coretti, C. Cumani, G. Cupani, S. Deiries, H. Dekker, B. Delabre, O. Demangeon, P. D. Marcantonio, D. Ehrenreich, A. Fragoso, L. Genolet, M. Genoni, R. G. Santos, I. Hughes, O. Iwert, J. Knudstrup, M. Landoni, J. Lizon, C. Maire, A. Manescau, C. Martins, D. M'egevand, P. Molaro, M. Monteiro, M. Monteiro, M. Moschetti, E. Mueller, L. Oggioni, A. Oliveira, M. Oshagh, G. Pariani, L. Pasquini, E. Poretti, J. L. Rasilla, E. Redaelli, M. Riva, S. Tschudi, P. Sant","doi":"10.1051/0004-6361/202038187","DOIUrl":"https://doi.org/10.1051/0004-6361/202038187","url":null,"abstract":"We characterized the transiting planetary system orbiting the G2V star K2-38 using the new-generation echelle spectrograph ESPRESSO. We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets. Using 43 ESPRESSO high-precision radial velocity measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a MCMC analysis, significantly improving their mass measurements. Using ESPRESSO spectra, we derived the stellar parameters, $T_{rm eff}$=5731$pm$66, $log g$=4.38$pm$0.11~dex, and $[Fe/H]$=0.26$pm$0.05~dex, and thus the mass and radius of K2-38, $M_{star}$=1.03 $^{+0.04}_{-0.02}$~M$_{oplus}$ and $R_{star}$=1.06 $^{+0.09}_{-0.06}$~R$_{oplus}$. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with $R_{rm P}$=1.54$pm$0.14~R$_{rm oplus}$ and $M_{rm p}$=7.3$^{+1.1}_{-1.0}$~M$_{oplus}$, and K2-38c as a sub-Neptune with $R_{rm P}$=2.29$pm$0.26~R$_{rm oplus}$ and $M_{rm p}$=8.3$^{+1.3}_{-1.3}$~M$_{oplus}$. We derived a mean density of $rho_{rm p}$=11.0$^{+4.1}_{-2.8}$~g cm$^{-3}$ for K2-38b and $rho_{rm p}$=3.8$^{+1.8}_{-1.1}$~g~cm$^{-3}$ for K2-38c, confirming K2-38b as one of the densest planets known to date. The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky model with a H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the radial velocity time-series whose origin could be linked to a 0.25-3~M$_{rm J}$ planet or stellar activity.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78237690","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 : 2020-06-26DOI: 10.1103/physrevresearch.2.043076
B. Thomas, Cody L. Ratterman
Ozone in Earth's atmosphere is known to have a radiative forcing effect on climate. Motivated by geochemical evidence for one or more nearby supernovae about 2.6 million years ago, we have investigated the question of whether a supernova at about 50 pc could cause a change in Earth's climate through its impact on atmospheric ozone concentrations. We used the "Planet Simulator" (PlaSim) intermediate-complexity climate model with prescribed ozone profiles taken from existing atmospheric chemistry modeling. We found that the effect on globally averaged surface temperature is small, but localized changes are larger and differences in atmospheric circulation and precipitation patterns could be significant regionally.
{"title":"Ozone depletion-induced climate change following a 50 pc supernova","authors":"B. Thomas, Cody L. Ratterman","doi":"10.1103/physrevresearch.2.043076","DOIUrl":"https://doi.org/10.1103/physrevresearch.2.043076","url":null,"abstract":"Ozone in Earth's atmosphere is known to have a radiative forcing effect on climate. Motivated by geochemical evidence for one or more nearby supernovae about 2.6 million years ago, we have investigated the question of whether a supernova at about 50 pc could cause a change in Earth's climate through its impact on atmospheric ozone concentrations. We used the \"Planet Simulator\" (PlaSim) intermediate-complexity climate model with prescribed ozone profiles taken from existing atmospheric chemistry modeling. We found that the effect on globally averaged surface temperature is small, but localized changes are larger and differences in atmospheric circulation and precipitation patterns could be significant regionally.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"136 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90797460","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 : 2020-06-25DOI: 10.1002/9781119815624.ch32
E. Roussos, P. Kollmann
The era of outer planet orbiters (Galileo, Juno and Cassini) is advancing our understanding of how the radiation belts of Jupiter and Saturn are structured, form and evolve well beyond what had been possible during the age of flyby missions and ground-based observations. The nearly two decades-long datasets of these missions, in the context of detailed and long-term observations of Earth's radiation belts, highlight which of the processes that accelerate particles to relativistic kinetic energies and limit their flux intensity can be considered more universal, and thus key for most extraterrestrial magnetospheres, and which reflect the unique aspects of each planet and its magnetospheric system. In this chapter we focus on the in-situ radiation belt observations in the context of theory, simulations and relevant measurements by Earth-based observatories. We describe both the average state and the time variations of Jupiter's and Saturn's radiation belts and associate them with specific physical processes.
{"title":"The Radiation Belts of Jupiter and Saturn","authors":"E. Roussos, P. Kollmann","doi":"10.1002/9781119815624.ch32","DOIUrl":"https://doi.org/10.1002/9781119815624.ch32","url":null,"abstract":"The era of outer planet orbiters (Galileo, Juno and Cassini) is advancing our understanding of how the radiation belts of Jupiter and Saturn are structured, form and evolve well beyond what had been possible during the age of flyby missions and ground-based observations. The nearly two decades-long datasets of these missions, in the context of detailed and long-term observations of Earth's radiation belts, highlight which of the processes that accelerate particles to relativistic kinetic energies and limit their flux intensity can be considered more universal, and thus key for most extraterrestrial magnetospheres, and which reflect the unique aspects of each planet and its magnetospheric system. In this chapter we focus on the in-situ radiation belt observations in the context of theory, simulations and relevant measurements by Earth-based observatories. We describe both the average state and the time variations of Jupiter's and Saturn's radiation belts and associate them with specific physical processes.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85380441","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 : 2020-06-24DOI: 10.1051/0004-6361/201937392
E. Ducrot, M. Gillon, L. Delrez, E. Agol, P. Rimmer, M. Turbet, M. Günther, B. Demory, A. Triaud, É. Bolmont, A. Burgasser, S. Carey, J. Ingalls, E. Jehin, J. Leconte, S. Lederer, D. Queloz, S. Raymond, F. Selsis, V. Grootel, J. Wit
With more than 1000 hours of observation from Feb 2016 to Oct 2019, the Spitzer Exploration Program Red Worlds (ID: 13067, 13175 and 14223) exclusively targeted TRAPPIST-1, a nearby (12pc) ultracool dwarf star orbited by seven transiting Earth-sized planets, all well-suited for a detailed atmospheric characterization with the upcoming JWST. In this paper, we present the global results of the project. We analyzed 88 new transits and combined them with 100 previously analyzed transits, for a total of 188 transits observed at 3.6 or 4.5 $mu$m. We also analyzed 29 occultations (secondary eclipses) of planet b and eight occultations of planet c observed at 4.5 $mu$m to constrain the brightness temperatures of their daysides. We identify several orphan transit-like structures in our Spitzer photometry, but all of them are of low significance. We do not confirm any new transiting planets. We estimate for TRAPPIST-1 transit depth measurements mean noise floors of $sim$35 and 25 ppm in channels 1 and 2 of Spitzer/IRAC, respectively. most of this noise floor is of instrumental origins and due to the large inter-pixel inhomogeneity of IRAC InSb arrays, and that the much better interpixel homogeneity of JWST instruments should result in noise floors as low as 10ppm, which is low enough to enable the atmospheric characterization of the planets by transit transmission spectroscopy. We construct updated broadband transmission spectra for all seven planets which show consistent transit depths between the two Spitzer channels. We identify and model five distinct high energy flares in the whole dataset, and discuss our results in the context of habitability. Finally, we fail to detect occultation signals of planets b and c at 4.5 $mu$m, and can only set 3$sigma$ upper limits on their dayside brightness temperatures (611K for b 586K for c).
{"title":"TRAPPIST-1: Global results of the Spitzer Exploration Science Program Red Worlds","authors":"E. Ducrot, M. Gillon, L. Delrez, E. Agol, P. Rimmer, M. Turbet, M. Günther, B. Demory, A. Triaud, É. Bolmont, A. Burgasser, S. Carey, J. Ingalls, E. Jehin, J. Leconte, S. Lederer, D. Queloz, S. Raymond, F. Selsis, V. Grootel, J. Wit","doi":"10.1051/0004-6361/201937392","DOIUrl":"https://doi.org/10.1051/0004-6361/201937392","url":null,"abstract":"With more than 1000 hours of observation from Feb 2016 to Oct 2019, the Spitzer Exploration Program Red Worlds (ID: 13067, 13175 and 14223) exclusively targeted TRAPPIST-1, a nearby (12pc) ultracool dwarf star orbited by seven transiting Earth-sized planets, all well-suited for a detailed atmospheric characterization with the upcoming JWST. In this paper, we present the global results of the project. We analyzed 88 new transits and combined them with 100 previously analyzed transits, for a total of 188 transits observed at 3.6 or 4.5 $mu$m. We also analyzed 29 occultations (secondary eclipses) of planet b and eight occultations of planet c observed at 4.5 $mu$m to constrain the brightness temperatures of their daysides. We identify several orphan transit-like structures in our Spitzer photometry, but all of them are of low significance. We do not confirm any new transiting planets. We estimate for TRAPPIST-1 transit depth measurements mean noise floors of $sim$35 and 25 ppm in channels 1 and 2 of Spitzer/IRAC, respectively. most of this noise floor is of instrumental origins and due to the large inter-pixel inhomogeneity of IRAC InSb arrays, and that the much better interpixel homogeneity of JWST instruments should result in noise floors as low as 10ppm, which is low enough to enable the atmospheric characterization of the planets by transit transmission spectroscopy. We construct updated broadband transmission spectra for all seven planets which show consistent transit depths between the two Spitzer channels. We identify and model five distinct high energy flares in the whole dataset, and discuss our results in the context of habitability. Finally, we fail to detect occultation signals of planets b and c at 4.5 $mu$m, and can only set 3$sigma$ upper limits on their dayside brightness temperatures (611K for b 586K for c).","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"85 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76430636","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}
If a transiting exoplanet has a moon, that moon could be detected directly from the transit itproduces itself, or indirectly via the transit timing variations it produces in its parent planet. There is a range of parameter space where the Kepler Space Telescope is sensitive to the TTVs exomoons might produce, though the moons themselves would be too small to detect photometrically via their own transits. The Earth's Moon, for example, produces TTVs of 2.6 minutes amplitude by causing our planet to move around their mutual center of mass. This ismore than Kepler's short-cadence interval of 1 minute and so nominally detectable (if transit timings are of comparable accuracy), even though the Moon's transit signatureis only 7% that of Earth's, well below Kepler's nominal threshold. Here we explore eight systems from the Kepler data set to examine the exomoon hypothesisas an explanation for their transit timing variations, which we compare with the alternatehypothesis that the TTVs are caused by an non-transiting planet in the system. We find that the TTVs of six of these systems could be plausibly explained by an exomoon, the size of which would not be nominally detectable by Kepler. Though we also find that the TTVsc ould be equally well reproduced by the presence of a non-transiting planet in the system, the observations are nevertheless completely consistent with a existence of a dynamically stablemoon small enough to fall below Kepler's photometric threshold for transit detection, and these systems warrant further observation and analysis.
{"title":"Exomoon candidates from transit timing variations: eight Kepler systems with TTVs explainable by photometrically unseen exomoons","authors":"C. Fox, P. Wiegert","doi":"10.1093/mnras/staa3743","DOIUrl":"https://doi.org/10.1093/mnras/staa3743","url":null,"abstract":"If a transiting exoplanet has a moon, that moon could be detected directly from the transit itproduces itself, or indirectly via the transit timing variations it produces in its parent planet. There is a range of parameter space where the Kepler Space Telescope is sensitive to the TTVs exomoons might produce, though the moons themselves would be too small to detect photometrically via their own transits. The Earth's Moon, for example, produces TTVs of 2.6 minutes amplitude by causing our planet to move around their mutual center of mass. This ismore than Kepler's short-cadence interval of 1 minute and so nominally detectable (if transit timings are of comparable accuracy), even though the Moon's transit signatureis only 7% that of Earth's, well below Kepler's nominal threshold. Here we explore eight systems from the Kepler data set to examine the exomoon hypothesisas an explanation for their transit timing variations, which we compare with the alternatehypothesis that the TTVs are caused by an non-transiting planet in the system. We find that the TTVs of six of these systems could be plausibly explained by an exomoon, the size of which would not be nominally detectable by Kepler. Though we also find that the TTVsc ould be equally well reproduced by the presence of a non-transiting planet in the system, the observations are nevertheless completely consistent with a existence of a dynamically stablemoon small enough to fall below Kepler's photometric threshold for transit detection, and these systems warrant further observation and analysis.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76292391","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}
Jon Fernandez Otegi, C. Dorn, R. Helled, F. Bouchy, J. Haldemann, Y. Alibert
Exoplanet characterization is one of the main foci of current exoplanetary science. For super-Earths and sub-Neptunes, we mostly rely on mass and radius measurements, which allow to derive the body's mean density and give a rough estimate of the planet's bulk composition. However, the determination of planetary interiors is a very challenging task. In addition to the uncertainty in the observed fundamental parameters, theoretical models are limited due to the degeneracy in determining the planetary composition. We aim to study several aspects that affect internal characterization of super-Earths and sub-Neptunes: observational uncertainties, location on the M-R diagram, impact of additional constraints as bulk abundances or irradiation, and model assumptions. We use a full probabilistic Bayesian inference analysis that accounts for observational and model uncertainties. We employ a Nested Sampling scheme to efficiently produce the posterior probability distributions for all the planetary structural parameter of interest. We include a structural model based on self-consistent thermodynamics of core, mantle, high-pressure ice, liquid water, and H-He envelope. Regarding the effect of mass and radius uncertainties on the determination of the internal structure, we find three different regimes: below the Earth-like composition line and above the pure-water composition line smaller observational uncertainties lead to better determination of the core and atmosphere mass respectively, and between them structure characterization only weakly depends on the observational uncertainties. We show that small variations in the temperature or entropy profiles lead to radius variations that are comparable to the observational uncertainty, suggesting that uncertainties linked to model assumptions can become more relevant to determine the internal structure than observational uncertainties.
{"title":"The impact of exoplanets' measured parameters on the inferred internal structure.","authors":"Jon Fernandez Otegi, C. Dorn, R. Helled, F. Bouchy, J. Haldemann, Y. Alibert","doi":"10.5194/epsc2020-721","DOIUrl":"https://doi.org/10.5194/epsc2020-721","url":null,"abstract":"Exoplanet characterization is one of the main foci of current exoplanetary science. For super-Earths and sub-Neptunes, we mostly rely on mass and radius measurements, which allow to derive the body's mean density and give a rough estimate of the planet's bulk composition. However, the determination of planetary interiors is a very challenging task. In addition to the uncertainty in the observed fundamental parameters, theoretical models are limited due to the degeneracy in determining the planetary composition. We aim to study several aspects that affect internal characterization of super-Earths and sub-Neptunes: observational uncertainties, location on the M-R diagram, impact of additional constraints as bulk abundances or irradiation, and model assumptions. We use a full probabilistic Bayesian inference analysis that accounts for observational and model uncertainties. We employ a Nested Sampling scheme to efficiently produce the posterior probability distributions for all the planetary structural parameter of interest. We include a structural model based on self-consistent thermodynamics of core, mantle, high-pressure ice, liquid water, and H-He envelope. Regarding the effect of mass and radius uncertainties on the determination of the internal structure, we find three different regimes: below the Earth-like composition line and above the pure-water composition line smaller observational uncertainties lead to better determination of the core and atmosphere mass respectively, and between them structure characterization only weakly depends on the observational uncertainties. We show that small variations in the temperature or entropy profiles lead to radius variations that are comparable to the observational uncertainty, suggesting that uncertainties linked to model assumptions can become more relevant to determine the internal structure than observational uncertainties.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84423655","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}
Planetary systems with sufficiently small orbital spacings can experience planetary mergers and ejections. The branching ratio of mergers vs ejections depends sensitively on the treatment of planetary close encounters. Previous works have adopted a simple "sticky-sphere" prescription, whose validity is questionable. We apply both smoothed particle hydrodynamics and $N$-body integrations to investigate the fluid effects in close encounters between gas giants and the long-term evolution of closely-packed planetary systems. Focusing on parabolic encounters between Jupiter-like planets with $M_J$ and $2M_J$, we find that quick mergers occur when the impact parameter $r_p$ (the pericenter separation between the planets) is less than $2R_J$, and the merger conserved 97% of the initial mass. Strong tidal effects can affect the "binary-planet" orbit when $r_p$ is between $2R_J$ and $4R_J$. We quantify these effects using a set of fitting formulae that can be implemented in $N$-body codes. We run a suite of $N$-body simulations with and without the formulae for systems of two giant planets initially in unstable, nearly circular coplanar orbits. The fluid (tidal) effects significantly increase the branching ratio of planetary mergers relative to ejections by doubling the effective collision radius. While the fluid effects do not change the distributions of semi-major axis and eccentricity of each type of remnant planets (mergers vs surviving planets in ejections), the overall orbital properties of planet scattering remnants are strongly affected due to the change in the branching ratio. We also find that the merger products have broad distributions of spin magnitudes and obliquities.
{"title":"Giant planet scatterings and collisions: hydrodynamics, merger-ejection branching ratio, and properties of the remnants","authors":"Jiaru Li, D. Lai, Kassandra R. Anderson, Bonan Pu","doi":"10.1093/mnras/staa3779","DOIUrl":"https://doi.org/10.1093/mnras/staa3779","url":null,"abstract":"Planetary systems with sufficiently small orbital spacings can experience planetary mergers and ejections. The branching ratio of mergers vs ejections depends sensitively on the treatment of planetary close encounters. Previous works have adopted a simple \"sticky-sphere\" prescription, whose validity is questionable. We apply both smoothed particle hydrodynamics and $N$-body integrations to investigate the fluid effects in close encounters between gas giants and the long-term evolution of closely-packed planetary systems. Focusing on parabolic encounters between Jupiter-like planets with $M_J$ and $2M_J$, we find that quick mergers occur when the impact parameter $r_p$ (the pericenter separation between the planets) is less than $2R_J$, and the merger conserved 97% of the initial mass. Strong tidal effects can affect the \"binary-planet\" orbit when $r_p$ is between $2R_J$ and $4R_J$. We quantify these effects using a set of fitting formulae that can be implemented in $N$-body codes. We run a suite of $N$-body simulations with and without the formulae for systems of two giant planets initially in unstable, nearly circular coplanar orbits. The fluid (tidal) effects significantly increase the branching ratio of planetary mergers relative to ejections by doubling the effective collision radius. While the fluid effects do not change the distributions of semi-major axis and eccentricity of each type of remnant planets (mergers vs surviving planets in ejections), the overall orbital properties of planet scattering remnants are strongly affected due to the change in the branching ratio. We also find that the merger products have broad distributions of spin magnitudes and obliquities.","PeriodicalId":8428,"journal":{"name":"arXiv: Earth and Planetary Astrophysics","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74653358","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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