Michalis Gaitanas, Christos Efthymiopoulos, Ioannis Gkolias, George Voyatzis, Kleomenis Tsiganis
We study the perturbed-from-synchronous librational state of a double asteroid, modeled by the Full Two Rigid Body Problem (F2RBP), with primary emphasis on deriving analytical formulas which describe the system's evolution after deflection by a kinetic impactor. To this end, both a linear and nonlinear (canonical) theory are developed. We make the simplifying approximations (to be relaxed in a forthcoming paper) of planar binary orbit and axisymmetric shape of the primary body. To study the effect of a DART-like hit on the secondary body, the momentum transfer enhancement parameter $beta$ is introduced and retained as a symbolic variable throughout all formulas derived, either by linear or nonlinear theory. Our approach can be of use in the context of the analysis of the post impact data from kinetic impactor missions, by providing a precise modeling of the impactor's effect on the seconadry's librational state as a function of $beta$.
{"title":"Analytical theory of the spin-orbit state of a binary asteroid deflected by a kinetic impactor","authors":"Michalis Gaitanas, Christos Efthymiopoulos, Ioannis Gkolias, George Voyatzis, Kleomenis Tsiganis","doi":"arxiv-2409.06534","DOIUrl":"https://doi.org/arxiv-2409.06534","url":null,"abstract":"We study the perturbed-from-synchronous librational state of a double\u0000asteroid, modeled by the Full Two Rigid Body Problem (F2RBP), with primary\u0000emphasis on deriving analytical formulas which describe the system's evolution\u0000after deflection by a kinetic impactor. To this end, both a linear and\u0000nonlinear (canonical) theory are developed. We make the simplifying\u0000approximations (to be relaxed in a forthcoming paper) of planar binary orbit\u0000and axisymmetric shape of the primary body. To study the effect of a DART-like\u0000hit on the secondary body, the momentum transfer enhancement parameter $beta$\u0000is introduced and retained as a symbolic variable throughout all formulas\u0000derived, either by linear or nonlinear theory. Our approach can be of use in\u0000the context of the analysis of the post impact data from kinetic impactor\u0000missions, by providing a precise modeling of the impactor's effect on the\u0000seconadry's librational state as a function of $beta$.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204585","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}
Sunho Jin, Masateru Ishiguro, Jooyeon Geem, Hiroyuki Naito, Jun Takahashi, Hiroshi Akitaya, Daisuke Kuroda, Seitaro Urakawa, Seiko Takagi, Tatsuharu Oono, Tomohiko Sekiguchi, Davide Perna, Simone Ieva, Yoonsoo P. Bach, Ryo Imazawa, Koji S. Kawabata, Makoto Watanabe, Hangbin Jo
Context. (4015) Wilson-Harrington (hereafter, WH) was discovered as a comet in 1949 but has a dynamical property consistent with that of a near-Earth asteroid. Although there is a report that the 1949 activity is associated with an ion tail, the cause of the activity has not yet been identified. Aims. This work aims to reveal the mysterious comet-like activity of the near-Earth asteroid. Methods. We conducted new polarimetric observations of WH from May 2022 to January 2023, reanalyses of the photographic plate images taken at the time of its discovery in 1949, and dust tail simulation modelings, where the dust terminal velocity and ejection epoch are taken into account. Results. We found that this object shows polarization characteristics similar to those of low-albedo asteroids. We derived the geometric albedo ranging from pV = 0.076 +- 0.010 to pV = 0.094 +- 0.018 from our polarimetry (the values vary depending on the data used for fitting and the slope-albedo relationship coefficients). In addition, the 1949 image showed an increase in brightness around the nucleus. Furthermore, we found that the color of the tail is consistent with sunlight, suggesting that the 1949 activity is associated with dust ejection. From the dust tail analysis, ~9 x 10^5 kg of material was ejected episodically at a low velocity equivalent to or even slower than the escape velocity. Conclusions. We conclude that WH is most likely an active asteroid of main belt origin and that the activity in 1949 was likely triggered by mass shedding due to fast rotation.
{"title":"New evidence supporting past dust ejections from active asteroid (4015) Wilson-Harrington","authors":"Sunho Jin, Masateru Ishiguro, Jooyeon Geem, Hiroyuki Naito, Jun Takahashi, Hiroshi Akitaya, Daisuke Kuroda, Seitaro Urakawa, Seiko Takagi, Tatsuharu Oono, Tomohiko Sekiguchi, Davide Perna, Simone Ieva, Yoonsoo P. Bach, Ryo Imazawa, Koji S. Kawabata, Makoto Watanabe, Hangbin Jo","doi":"arxiv-2409.06448","DOIUrl":"https://doi.org/arxiv-2409.06448","url":null,"abstract":"Context. (4015) Wilson-Harrington (hereafter, WH) was discovered as a comet\u0000in 1949 but has a dynamical property consistent with that of a near-Earth\u0000asteroid. Although there is a report that the 1949 activity is associated with\u0000an ion tail, the cause of the activity has not yet been identified. Aims. This\u0000work aims to reveal the mysterious comet-like activity of the near-Earth\u0000asteroid. Methods. We conducted new polarimetric observations of WH from May\u00002022 to January 2023, reanalyses of the photographic plate images taken at the\u0000time of its discovery in 1949, and dust tail simulation modelings, where the\u0000dust terminal velocity and ejection epoch are taken into account. Results. We\u0000found that this object shows polarization characteristics similar to those of\u0000low-albedo asteroids. We derived the geometric albedo ranging from pV = 0.076\u0000+- 0.010 to pV = 0.094 +- 0.018 from our polarimetry (the values vary depending\u0000on the data used for fitting and the slope-albedo relationship coefficients).\u0000In addition, the 1949 image showed an increase in brightness around the\u0000nucleus. Furthermore, we found that the color of the tail is consistent with\u0000sunlight, suggesting that the 1949 activity is associated with dust ejection.\u0000From the dust tail analysis, ~9 x 10^5 kg of material was ejected episodically\u0000at a low velocity equivalent to or even slower than the escape velocity.\u0000Conclusions. We conclude that WH is most likely an active asteroid of main belt\u0000origin and that the activity in 1949 was likely triggered by mass shedding due\u0000to fast rotation.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204586","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}
Cindy N. Luu, Xinting Yu, Christopher R. Glein, Hamish Innes, Artyom Aguichine, Joshua Krissansen-Totton, Julianne I. Moses, Shang-Min Tsai, Xi Zhang, Ngoc Truong, Jonathan J. Fortney
Temperate exoplanets between the sizes of Earth and Neptune, known as "sub-Neptunes", have emerged as intriguing targets for astrobiology. It is unknown whether these planets resemble Earth-like terrestrial worlds with a habitable surface, Neptune-like giant planets with deep atmospheres and no habitable surface, or something exotic in between. Recent JWST transmission spectroscopy observations of the canonical sub-Neptune K2-18 b revealed ~1% CH4, ~1% CO2, and a non-detection of CO in the atmosphere. While previous studies have proposed that the observed atmospheric composition could help constrain the lower atmosphere conditions and determine the interior structure of sub-Neptunes like K2-18 b, the possible interactions between the atmosphere and a hot, supercritical water ocean at its base remain unexplored. In this work, we investigate whether a global supercritical water ocean, resembling a planetary-scale hydrothermal system, can explain these observations on K2-18 b-like sub-Neptunes through equilibrium aqueous geochemical calculations. We find that the observed atmospheric CH4/CO2 ratio implies a minimum ocean temperature of ~715 K, whereas the corresponding CO/CO2 ratio allows ocean temperatures up to ~1060 K. These results indicate that a global supercritical water ocean on K2-18 b is plausible. While life cannot survive in this ocean, this work represents the first step towards understanding how a global supercritical water ocean may influence observable atmospheric characteristics on volatile-rich sub-Neptunes. Future observations with better constrained NH3 and CO mixing ratios could further help distinguish between possible interior compositions of K2-18 b.
大小介于地球和海王星之间的温带系外行星，被称为 "亚海王星"，已经成为天体生物学的有趣目标。目前尚不清楚这些行星是类似于具有可居住表面的类地行星，还是类似于具有深层大气但没有可居住表面的海王星巨行星，抑或是介于两者之间的奇特行星。JWST 最近对典型的亚海王星 K2-18 b 进行的透射光谱观测显示，其大气中约有 1%的 CH4、约有 1%的 CO2，没有检测到 CO。尽管之前的研究提出，观测到的大气成分有助于约束低层大气条件，并确定像K2-18 b这样的亚海王星的内部结构，但大气层与其底部的热超临界水海洋之间可能存在的相互作用仍未得到探索。在这项工作中，我们通过平衡水地球化学计算，研究了类似行星尺度热液系统的全球超临界水海洋能否解释在 K2-18b 类海王星上的这些观测结果。我们发现，观测到的大气中 CH4/CO2 比率意味着最低海洋温度约为 715 K，而相应的 CO/CO2 比率允许海洋温度高达约 1060 K。虽然生命无法在这一海洋中生存，但这项工作代表着向了解全球超临界水海洋如何影响富含挥发性物质的次海王星上的可观测大气特征迈出的第一步。未来的观测如果能更好地约束 NH3 和 CO 的混合比，将有助于进一步区分 K2-18 b 可能的内部组成。
{"title":"Volatile-rich Sub-Neptunes as Hydrothermal Worlds: The Case of K2-18 b","authors":"Cindy N. Luu, Xinting Yu, Christopher R. Glein, Hamish Innes, Artyom Aguichine, Joshua Krissansen-Totton, Julianne I. Moses, Shang-Min Tsai, Xi Zhang, Ngoc Truong, Jonathan J. Fortney","doi":"arxiv-2409.06258","DOIUrl":"https://doi.org/arxiv-2409.06258","url":null,"abstract":"Temperate exoplanets between the sizes of Earth and Neptune, known as\u0000\"sub-Neptunes\", have emerged as intriguing targets for astrobiology. It is\u0000unknown whether these planets resemble Earth-like terrestrial worlds with a\u0000habitable surface, Neptune-like giant planets with deep atmospheres and no\u0000habitable surface, or something exotic in between. Recent JWST transmission\u0000spectroscopy observations of the canonical sub-Neptune K2-18 b revealed ~1%\u0000CH4, ~1% CO2, and a non-detection of CO in the atmosphere. While previous\u0000studies have proposed that the observed atmospheric composition could help\u0000constrain the lower atmosphere conditions and determine the interior structure\u0000of sub-Neptunes like K2-18 b, the possible interactions between the atmosphere\u0000and a hot, supercritical water ocean at its base remain unexplored. In this\u0000work, we investigate whether a global supercritical water ocean, resembling a\u0000planetary-scale hydrothermal system, can explain these observations on K2-18\u0000b-like sub-Neptunes through equilibrium aqueous geochemical calculations. We\u0000find that the observed atmospheric CH4/CO2 ratio implies a minimum ocean\u0000temperature of ~715 K, whereas the corresponding CO/CO2 ratio allows ocean\u0000temperatures up to ~1060 K. These results indicate that a global supercritical\u0000water ocean on K2-18 b is plausible. While life cannot survive in this ocean,\u0000this work represents the first step towards understanding how a global\u0000supercritical water ocean may influence observable atmospheric characteristics\u0000on volatile-rich sub-Neptunes. Future observations with better constrained NH3\u0000and CO mixing ratios could further help distinguish between possible interior\u0000compositions of K2-18 b.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204587","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}
Core accretion is the standard scenario of planet formation, wherein planets are formed by sequential accretion of gas and solids, and is widely used to interpret exoplanet observations. However, no direct probes of the scenario have been discussed yet. Here, we introduce an onion-like model as one idealization of sequential accretion and propose that bulk and atmospheric metallicities of exoplanets can be used as direct probes of the process. Our analytical calculations, coupled with observational data, demonstrate that the trend of observed exoplanets supports the sequential accretion hypothesis. In particular, accretion of planetesimals that are $gtrsim $ 100 km in size is most favored to consistently explain the observed trends. The importance of opening gaps in both planetesimal and gas disks following planetary growth is also identified. New classification is proposed, wherein most observed planets are classified into two interior statuses: globally mixed and locally (well-)mixed. Explicit identification of the locally (well-)mixed status enables reliable verification of sequential accretion. During the JWST era, the quality and volume of observational data will increase drastically and improve exoplanet characterization. This work provides one key reference of how both the bulk and atmospheric metallicities can be used to constrain gas and solid accretion mechanisms of planets.
{"title":"Bulk and atmospheric metallicities as direct probes of sequentially varying accretion mechanisms of gas and solids onto planets","authors":"Yasuhiro Hasegawa, Mark R. Swain","doi":"arxiv-2409.06670","DOIUrl":"https://doi.org/arxiv-2409.06670","url":null,"abstract":"Core accretion is the standard scenario of planet formation, wherein planets\u0000are formed by sequential accretion of gas and solids, and is widely used to\u0000interpret exoplanet observations. However, no direct probes of the scenario\u0000have been discussed yet. Here, we introduce an onion-like model as one\u0000idealization of sequential accretion and propose that bulk and atmospheric\u0000metallicities of exoplanets can be used as direct probes of the process. Our\u0000analytical calculations, coupled with observational data, demonstrate that the\u0000trend of observed exoplanets supports the sequential accretion hypothesis. In\u0000particular, accretion of planetesimals that are $gtrsim $ 100 km in size is\u0000most favored to consistently explain the observed trends. The importance of\u0000opening gaps in both planetesimal and gas disks following planetary growth is\u0000also identified. New classification is proposed, wherein most observed planets\u0000are classified into two interior statuses: globally mixed and locally\u0000(well-)mixed. Explicit identification of the locally (well-)mixed status\u0000enables reliable verification of sequential accretion. During the JWST era, the\u0000quality and volume of observational data will increase drastically and improve\u0000exoplanet characterization. This work provides one key reference of how both\u0000the bulk and atmospheric metallicities can be used to constrain gas and solid\u0000accretion mechanisms of planets.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204584","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}
Jack Lubin, Erik A. Petigura, Judah Van Zandt, Corey Beard, Fei Dai, Samuel Halverson, Rae Holcomb, Andrew W. Howard, Howard Isaacson, Jacob Luhn, Paul Robertson, Ryan A. Rubenzahl, Gudmundur Stefansson, Joshua N. Winn, Max Brodheim, William Deich, Grant M. Hill, Steven R. Gibson, Bradford Holden, Aaron Householder, Russ R. Laher, Kyle Lanclos, Joel Payne, Arpita Roy, Roger Smith, Abby P. Shaum, Christian Schwab, Josh Walawender
We report the sky-projected spin-orbit angle $lambda$ for HD 191939 b, the innermost planet in a 6 planet system, using Keck/KPF to detect the Rossiter-McLaughlin (RM) effect. Planet b is a sub-Neptune with radius 3.4 $pm$ 0.8 R$_{oplus}$ and mass 10.0 $pm$ 0.7 M$_{oplus}$ with an RM amplitude $<$1 ms$^{-1}$. We find the planet is consistent with a well-aligned orbit, measuring $lambda= , $ 3.7 $pm$ 5.0 degrees. Additionally, we place new constraints on the mass and period of the distant super-Jupiter, planet f, finding it to be 2.88 $pm$ 0.26 $M_J$ on a 2898 $pm$ 152 day orbit. With these new orbital parameters, we perform a dynamical analysis of the system and constrain the mutual inclination of the non-transiting planet e to be smaller than 12 degrees relative to the plane shared by the inner three transiting planets. Additionally, the further planet f is inclined off this shared plane, the greater the amplitude of precession for the entire inner system, making it increasingly unlikely to measure an aligned orbit for planet b. Through this analysis, we show that this system's wide variety of planets are all well-aligned with the star and nearly co-planar, suggesting that the system formed dynamically cold and flat out of a well-aligned proto-planetary disk, similar to our own solar system.
{"title":"The HD 191939 Exoplanet System is Well-Aligned and Flat","authors":"Jack Lubin, Erik A. Petigura, Judah Van Zandt, Corey Beard, Fei Dai, Samuel Halverson, Rae Holcomb, Andrew W. Howard, Howard Isaacson, Jacob Luhn, Paul Robertson, Ryan A. Rubenzahl, Gudmundur Stefansson, Joshua N. Winn, Max Brodheim, William Deich, Grant M. Hill, Steven R. Gibson, Bradford Holden, Aaron Householder, Russ R. Laher, Kyle Lanclos, Joel Payne, Arpita Roy, Roger Smith, Abby P. Shaum, Christian Schwab, Josh Walawender","doi":"arxiv-2409.06795","DOIUrl":"https://doi.org/arxiv-2409.06795","url":null,"abstract":"We report the sky-projected spin-orbit angle $lambda$ for HD 191939 b, the\u0000innermost planet in a 6 planet system, using Keck/KPF to detect the\u0000Rossiter-McLaughlin (RM) effect. Planet b is a sub-Neptune with radius 3.4\u0000$pm$ 0.8 R$_{oplus}$ and mass 10.0 $pm$ 0.7 M$_{oplus}$ with an RM\u0000amplitude $<$1 ms$^{-1}$. We find the planet is consistent with a well-aligned\u0000orbit, measuring $lambda= , $ 3.7 $pm$ 5.0 degrees. Additionally, we place\u0000new constraints on the mass and period of the distant super-Jupiter, planet f,\u0000finding it to be 2.88 $pm$ 0.26 $M_J$ on a 2898 $pm$ 152 day orbit. With\u0000these new orbital parameters, we perform a dynamical analysis of the system and\u0000constrain the mutual inclination of the non-transiting planet e to be smaller\u0000than 12 degrees relative to the plane shared by the inner three transiting\u0000planets. Additionally, the further planet f is inclined off this shared plane,\u0000the greater the amplitude of precession for the entire inner system, making it\u0000increasingly unlikely to measure an aligned orbit for planet b. Through this\u0000analysis, we show that this system's wide variety of planets are all\u0000well-aligned with the star and nearly co-planar, suggesting that the system\u0000formed dynamically cold and flat out of a well-aligned proto-planetary disk,\u0000similar to our own solar system.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204563","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}
Long-Fei Chen, Chao-Wei Tsai, Jian-Yang Li, Bin Yang, Di Li, Yan Duan, Chih-Hao Hsia, Zhichen Pan, Lei Qian, Donghui Quan, Xue-Jian Jiang, Xiaohu Li, Ruining Zhao, Pei Zuo
We used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward four comets, C/2020 F3 (NEOWISE), C/2020 R4 (ATLAS), C/2021 A1 (Leonard), and 67P/Churyumov-Gerasimenko during or after their perihelion passages. Thousands of molecular transition lines fall in this low-frequency range, many attributed to complex organic or prebiotic molecules. We conducted a blind search for the possible molecular lines in this frequency range in those comets and could not identify clear signals of molecular emissions in the data. Although several molecules have been detected at high frequencies of great than 100 GHz in comets, our results confirm that it is challenging to detect molecular transitions in the L-band frequency ranges. The non-detection of L-band molecular lines in the cometary environment could rule out the possibility of unusually strong lines, which could be caused by the masers or non-LTE effects. Although the line strengths are predicted to be weak, for FAST, using the ultra-wide bandwidth receiver and improving the radio frequency interference environments would enhance the detectability of those molecular transitions at low frequencies in the future.
我们利用五百米孔径球面射电望远镜（FAST）在 1.0 和 1.5 千兆赫之间的 L 波段对四颗彗星（C/2020 F3 (NEOWISE)、C/2020 R4 (ATLAS)、C/2021 A1 (Leonard) 和 67P/Churyumov-Gerasimenko 彗星）的近日点期间或之后的分子辐射进行了搜索。在这个低频范围内有数千条分子过渡线，其中许多是复杂的有机分子或前生物分子。我们对这些彗星中这一频率范围内可能存在的分子线进行了盲搜索，但无法在数据中识别出明确的分子发射信号。虽然在大于 100 千兆赫的高频率彗星上探测到了一些分子，但我们的结果证实，在 L 波段频率范围内探测到分子过渡具有挑战性。在彗星环境中未探测到 L 波段分子线可能排除了异常强的线的可能性，这些线可能是由 masers 或非 LTE 效应引起的。虽然预测线强度较弱，但对于 FAST 来说，使用超宽带接收器和改善射频干扰环境将在未来提高低频分子跃迁的可探测性。
{"title":"FAST Observations of Four Comets to Search for the Molecular Line Emissions between 1.0 and 1.5 GHz Frequencies","authors":"Long-Fei Chen, Chao-Wei Tsai, Jian-Yang Li, Bin Yang, Di Li, Yan Duan, Chih-Hao Hsia, Zhichen Pan, Lei Qian, Donghui Quan, Xue-Jian Jiang, Xiaohu Li, Ruining Zhao, Pei Zuo","doi":"arxiv-2409.06227","DOIUrl":"https://doi.org/arxiv-2409.06227","url":null,"abstract":"We used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to\u0000search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward\u0000four comets, C/2020 F3 (NEOWISE), C/2020 R4 (ATLAS), C/2021 A1 (Leonard), and\u000067P/Churyumov-Gerasimenko during or after their perihelion passages. Thousands\u0000of molecular transition lines fall in this low-frequency range, many attributed\u0000to complex organic or prebiotic molecules. We conducted a blind search for the\u0000possible molecular lines in this frequency range in those comets and could not\u0000identify clear signals of molecular emissions in the data. Although several\u0000molecules have been detected at high frequencies of great than 100 GHz in\u0000comets, our results confirm that it is challenging to detect molecular\u0000transitions in the L-band frequency ranges. The non-detection of L-band\u0000molecular lines in the cometary environment could rule out the possibility of\u0000unusually strong lines, which could be caused by the masers or non-LTE effects.\u0000Although the line strengths are predicted to be weak, for FAST, using the\u0000ultra-wide bandwidth receiver and improving the radio frequency interference\u0000environments would enhance the detectability of those molecular transitions at\u0000low frequencies in the future.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204588","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}
Super-puffs are low-density planets of unknown origin and composition. If they form by accreting nebular gas through a circumplanetary disk, one might expect super-puffs to be spinning quickly. Here, we derive upper limits on the rotational oblateness of the super-puff Kepler-51d, based on precise transit observations with the NIRSpec instrument aboard the James Webb Space Telescope. The absence of detectable oblateness-related anomalies in the light curve leads to an upper limit of about $0.15$ on the planet's sky-projected oblateness. Assuming the sky-projected oblateness to be representative of the true oblateness, the rotation period of Kepler-51d is $gtrsim 40$ hours, or equivalently, its rotation speed is $lesssim 42%$ of the breakup speed. Alternatively, if the apparently low density of Kepler-51d is due to an opaque planetary ring, the ring must be oriented within $27deg$ of face-on and have an inner radius smaller than $1.2$ times the planet's radius. The lack of anomalies exceeding $0.01%$ in the ingress and egress portions of the light curve also places a constraint on the model of Wang & Dai, in which the planet's apparently low density is due to a dusty outflowing atmosphere.
超级泡芙是起源和成分不明的低密度行星。如果它们是通过环行星盘吸积星云气体形成的，那么人们可能会期待超级泡芙快速旋转。这里，我们根据詹姆斯-韦伯太空望远镜（James Webb Space Telescope）上的近红外望远镜（NIRSpec）的精确凌日观测，推导出了超级泡芙 Kepler-51d 的旋转扁圆度上限。另外，如果开普勒-51d表面上的低密度是由于一个不透明的行星环造成的，那么这个行星环的方向必须在面朝上的27deg以内，并且其内半径小于行星半径的1.2倍。在光曲线的入口和出口部分缺乏超过0.01美元/%$的异常，这也对Wang和Dai的模型施加了限制，在他们的模型中，行星明显的低密度是由于尘埃外流大气造成的。
{"title":"Slow Rotation for the Super-Puff Planet Kepler-51d","authors":"Caleb Lammers, Joshua N. Winn","doi":"arxiv-2409.06697","DOIUrl":"https://doi.org/arxiv-2409.06697","url":null,"abstract":"Super-puffs are low-density planets of unknown origin and composition. If\u0000they form by accreting nebular gas through a circumplanetary disk, one might\u0000expect super-puffs to be spinning quickly. Here, we derive upper limits on the\u0000rotational oblateness of the super-puff Kepler-51d, based on precise transit\u0000observations with the NIRSpec instrument aboard the James Webb Space Telescope.\u0000The absence of detectable oblateness-related anomalies in the light curve leads\u0000to an upper limit of about $0.15$ on the planet's sky-projected oblateness.\u0000Assuming the sky-projected oblateness to be representative of the true\u0000oblateness, the rotation period of Kepler-51d is $gtrsim 40$ hours, or\u0000equivalently, its rotation speed is $lesssim 42%$ of the breakup speed.\u0000Alternatively, if the apparently low density of Kepler-51d is due to an opaque\u0000planetary ring, the ring must be oriented within $27deg$ of face-on and have\u0000an inner radius smaller than $1.2$ times the planet's radius. The lack of\u0000anomalies exceeding $0.01%$ in the ingress and egress portions of the light\u0000curve also places a constraint on the model of Wang & Dai, in which the\u0000planet's apparently low density is due to a dusty outflowing atmosphere.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"403 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204564","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}
Conventional planet formation theories predict a paucity of massive planets around small stars, especially very low-mass ($0.1 - 0.3 M_{odot}$) mid-to-late M dwarfs. Such tiny stars are expected to form planets of terrestrial sizes, but not much bigger. However, this expectation is challenged by the recent discovery of LHS 3154 b, a planet with period of 3.7 days and minimum mass of $13.2 M_{oplus}$ orbiting a $0.11 M_{odot}$ star. Here, we propose that close-in Neptune-mass planets like LHS 3154 b formed through an anomalous series of mergers from a primordial compact system of super-Earths. We perform simulations within the context of the "breaking the chains" scenario, in which super-Earths initially form in tightly-spaced chains of mean-motion resonances before experiencing dynamical instabilities and collisions. Planets as massive and close-in as LHS 3154 b ($M_p sim 12 - 20 M_{oplus}$, $P < 7$ days) are produced in $sim$1% of simulated systems, in broad agreement with their low observed occurrence. These results suggest that such planets do not require particularly unusual formation conditions but rather are an occasional byproduct of a process that is already theorized to explain compact multi-planet systems. Interestingly, our simulated systems with LHS 3154 b-like planets also contain smaller planets at around $sim 30$ days, offering a possible test of this hypothesis.
{"title":"Formation of Close-in Neptunes Around Low-Mass Stars Through Breaking Resonant Chains","authors":"Donald Liveoak, Sarah Millholland","doi":"arxiv-2409.05748","DOIUrl":"https://doi.org/arxiv-2409.05748","url":null,"abstract":"Conventional planet formation theories predict a paucity of massive planets\u0000around small stars, especially very low-mass ($0.1 - 0.3 M_{odot}$)\u0000mid-to-late M dwarfs. Such tiny stars are expected to form planets of\u0000terrestrial sizes, but not much bigger. However, this expectation is challenged\u0000by the recent discovery of LHS 3154 b, a planet with period of 3.7 days and\u0000minimum mass of $13.2 M_{oplus}$ orbiting a $0.11 M_{odot}$ star. Here,\u0000we propose that close-in Neptune-mass planets like LHS 3154 b formed through an\u0000anomalous series of mergers from a primordial compact system of super-Earths.\u0000We perform simulations within the context of the \"breaking the chains\"\u0000scenario, in which super-Earths initially form in tightly-spaced chains of\u0000mean-motion resonances before experiencing dynamical instabilities and\u0000collisions. Planets as massive and close-in as LHS 3154 b ($M_p sim 12 - 20 \u0000M_{oplus}$, $P < 7$ days) are produced in $sim$1% of simulated systems, in\u0000broad agreement with their low observed occurrence. These results suggest that\u0000such planets do not require particularly unusual formation conditions but\u0000rather are an occasional byproduct of a process that is already theorized to\u0000explain compact multi-planet systems. Interestingly, our simulated systems with\u0000LHS 3154 b-like planets also contain smaller planets at around $sim 30$ days,\u0000offering a possible test of this hypothesis.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204593","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}
Zachariah Milby, Katherine de Kleer, Carl Schmidt, François Leblanc
Ganymede's aurora are the product of complex interactions between its intrinsic magnetosphere and the surrounding Jovian plasma environment and can be used to derive both atmospheric composition and density. In this study, we analyzed a time-series of Ganymede's optical aurora taken with Keck I/HIRES during eclipse by Jupiter on 2021-06-08 UTC, one day after the Juno flyby of Ganymede. The data had sufficient signal-to-noise in individual 5-minute observations to allow for the first high cadence analysis of the spatial distribution of the aurora brightness and the ratio between the 630.0 and 557.7 nm disk-integrated auroral brightnesses -- a quantity diagnostic of the relative abundances of O, O$_2$ and H$_2$O in Ganymede's atmosphere. We found that the hemisphere closer to the centrifugal equator of Jupiter's magnetosphere (where electron number density is highest) was up to twice as bright as the opposing hemisphere. The dusk (trailing) hemisphere, subjected to the highest flux of charged particles from Jupiter's magnetosphere, was also consistently almost twice as bright as the dawn (leading) hemisphere. We modeled emission from simulated O$_2$ and H$_2$O atmospheres during eclipse and found that if Ganymede hosts an H$_2$O sublimation atmosphere in sunlight, it must collapse on a faster timescale than expected to explain its absence in our data given our current understanding of Ganymede's surface properties.
{"title":"Short-Timescale Spatial Variability of Ganymede's Optical Aurora","authors":"Zachariah Milby, Katherine de Kleer, Carl Schmidt, François Leblanc","doi":"arxiv-2409.06055","DOIUrl":"https://doi.org/arxiv-2409.06055","url":null,"abstract":"Ganymede's aurora are the product of complex interactions between its\u0000intrinsic magnetosphere and the surrounding Jovian plasma environment and can\u0000be used to derive both atmospheric composition and density. In this study, we\u0000analyzed a time-series of Ganymede's optical aurora taken with Keck I/HIRES\u0000during eclipse by Jupiter on 2021-06-08 UTC, one day after the Juno flyby of\u0000Ganymede. The data had sufficient signal-to-noise in individual 5-minute\u0000observations to allow for the first high cadence analysis of the spatial\u0000distribution of the aurora brightness and the ratio between the 630.0 and 557.7\u0000nm disk-integrated auroral brightnesses -- a quantity diagnostic of the\u0000relative abundances of O, O$_2$ and H$_2$O in Ganymede's atmosphere. We found\u0000that the hemisphere closer to the centrifugal equator of Jupiter's\u0000magnetosphere (where electron number density is highest) was up to twice as\u0000bright as the opposing hemisphere. The dusk (trailing) hemisphere, subjected to\u0000the highest flux of charged particles from Jupiter's magnetosphere, was also\u0000consistently almost twice as bright as the dawn (leading) hemisphere. We\u0000modeled emission from simulated O$_2$ and H$_2$O atmospheres during eclipse and\u0000found that if Ganymede hosts an H$_2$O sublimation atmosphere in sunlight, it\u0000must collapse on a faster timescale than expected to explain its absence in our\u0000data given our current understanding of Ganymede's surface properties.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204590","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}
Chemeda Ejeta, Erika Gibb, Michael A. DiSanti, Hideyo Kawakita, Boncho P. Bonev, Neil Dello Russo, Nathan Roth, Younas Khan, Adam J. McKay, Michael R. Combi, Lori Feaga, Mohammad Saki, Ronald J. Vervack Jr., Yinsi Shou
Comet C/2017 K2 (Pan-STARRS) provided a rare opportunity to investigate the evolution of coma composition and outgassing patterns over a transitional heliocentric distance (Rh) range where activity drivers in comets are thought to change from "hypervolatile" (CO, CH$_4$, C$_2$H$_6$, and/or CO$_2$)-dominated to H2O-dominated. We performed high-resolution, cross-dispersed, near-infrared spectroscopy of C/2017 K2 with iSHELL at the NASA Infrared Telescope Facility (IRTF) and NIRSPEC at the W. M. Keck 2 Observatory. We report gas rotational temperatures (Trot) and molecular production rates (Q; mol/s) or upper limits for the hypervolatile species CH$_4$, CO, and C$_2$H$_6$, together with less volatile ices (CH$_3$OH, H$_2$O, HCN, C$_2$H$_2$, NH$_3$, and OCS) over a range of pre-perihelion distances, Rh= 3.15 - 2.35 au. We also report (or stringently constrain) abundance ratios (mixing ratios) of the targeted species with respect to CO, C$_2$H$_6$, and (when detected) H$_2$O. All volatiles were enriched relative to water in C/2017 K2 when compared to their mean values among Oort Cloud comets, whereas abundances relative to C2H6 were consistent with their average values from other long-period comets.
{"title":"Infrared Compositional Measurements in Comet C/2017 K2 (Pan-STARRS) at Heliocentric Distances Beyond 2.3 AU","authors":"Chemeda Ejeta, Erika Gibb, Michael A. DiSanti, Hideyo Kawakita, Boncho P. Bonev, Neil Dello Russo, Nathan Roth, Younas Khan, Adam J. McKay, Michael R. Combi, Lori Feaga, Mohammad Saki, Ronald J. Vervack Jr., Yinsi Shou","doi":"arxiv-2409.05789","DOIUrl":"https://doi.org/arxiv-2409.05789","url":null,"abstract":"Comet C/2017 K2 (Pan-STARRS) provided a rare opportunity to investigate the\u0000evolution of coma composition and outgassing patterns over a transitional\u0000heliocentric distance (Rh) range where activity drivers in comets are thought\u0000to change from \"hypervolatile\" (CO, CH$_4$, C$_2$H$_6$, and/or\u0000CO$_2$)-dominated to H2O-dominated. We performed high-resolution,\u0000cross-dispersed, near-infrared spectroscopy of C/2017 K2 with iSHELL at the\u0000NASA Infrared Telescope Facility (IRTF) and NIRSPEC at the W. M. Keck 2\u0000Observatory. We report gas rotational temperatures (Trot) and molecular\u0000production rates (Q; mol/s) or upper limits for the hypervolatile species\u0000CH$_4$, CO, and C$_2$H$_6$, together with less volatile ices (CH$_3$OH, H$_2$O,\u0000HCN, C$_2$H$_2$, NH$_3$, and OCS) over a range of pre-perihelion distances, Rh=\u00003.15 - 2.35 au. We also report (or stringently constrain) abundance ratios\u0000(mixing ratios) of the targeted species with respect to CO, C$_2$H$_6$, and\u0000(when detected) H$_2$O. All volatiles were enriched relative to water in C/2017\u0000K2 when compared to their mean values among Oort Cloud comets, whereas\u0000abundances relative to C2H6 were consistent with their average values from\u0000other long-period comets.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204591","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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