Nikku Madhusudhan, Savvas Constantinou, Måns Holmberg, Subhajit Sarkar, Anjali A. A. Piette and Julianne I. Moses
{"title":"New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI","authors":"Nikku Madhusudhan, Savvas Constantinou, Måns Holmberg, Subhajit Sarkar, Anjali A. A. Piette and Julianne I. Moses","doi":"10.3847/2041-8213/adc1c8","DOIUrl":"https://doi.org/10.3847/2041-8213/adc1c8","url":null,"abstract":"The sub-Neptune frontier has opened a new window into the rich diversity of planetary environments beyond the solar system. The possibility of hycean worlds, with planet-wide oceans and H2-rich atmospheres, significantly expands and accelerates the search for habitable environments elsewhere. Recent JWST transmission spectroscopy of the candidate hycean world K2-18 b in the near-infrared led to the first detections of the carbon-bearing molecules CH4 and CO2 in its atmosphere, with a composition consistent with predictions for hycean conditions. The observations also provided a tentative hint of dimethyl sulfide (DMS), a possible biosignature gas, but the inference was of low statistical significance. We report a mid-infrared transmission spectrum of K2-18 b obtained using the JWST MIRI LRS instrument in the ∼6–12 μm range. The spectrum shows distinct features and is inconsistent with a featureless spectrum at 3.4σ significance compared to our canonical model. We find that the spectrum cannot be explained by most molecules predicted for K2-18 b, with the exception of DMS and dimethyl disulfide (DMDS), also a potential biosignature gas. We report new independent evidence for DMS and/or DMDS in the atmosphere at 3σ significance, with high abundance (≳10 ppmv) of at least one of the two molecules. More observations are needed to increase the robustness of the findings and resolve the degeneracy between DMS and DMDS. The results also highlight the need for additional experimental and theoretical work to determine accurate cross sections of important biosignature gases and identify potential abiotic sources. We discuss the implications of the present findings for the possibility of biological activity on K2-18 b.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143841316","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}
Rena A. Lee, Fei Dai, Andrew W. Howard, Samuel Halverson, Jonathan Gomez Barrientos, Michael Greklek-McKeon, Heather A. Knutson, Benjamin J. Fulton, Guđmundur Stefánsson, Jack Lubin, Howard Isaacson, Casey L. Brinkman, Nicholas Saunders, Daniel Hey, Daniel Huber, Lauren M. Weiss, Leslie A. Rogers, Diana Valencia, Mykhaylo Plotnykov, Kimberly Paragas, Renyu Hu, Te Han, Erik A. Petigura, Ryan Rubenzahl, David R. Ciardi, Aaron Householder, Gregory J. Gilbert, J. M. Joel Ong, Jingwen Zhang, Jacob Luhn, Luke Handley, Corey Beard, Steven Giacalone, Rae Holcomb, Judah Van Zandt, Ashley D. Baker, Max Brodheim, Matt Brown, David Charbonneau, Karen A. Collins, Ian J. M. Crossfield, William Deich, Xavier Dumusque, Steven R. Gibson, Emily Gilbert, Grant M. Hill, Bradford Holden, Jon M. Jenkins, Stephen Kaye, Russ R. Laher, Kyle Lanclos, W. Garett Levine, Joel Payne, Alex S. Polanski, John O’Meara, George R. Ricker, Kodi Rider, Paul Robertson, Arpita Roy, Joshua E. Schlieder, Christian Sc..
{"title":"TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf","authors":"Rena A. Lee, Fei Dai, Andrew W. Howard, Samuel Halverson, Jonathan Gomez Barrientos, Michael Greklek-McKeon, Heather A. Knutson, Benjamin J. Fulton, Guđmundur Stefánsson, Jack Lubin, Howard Isaacson, Casey L. Brinkman, Nicholas Saunders, Daniel Hey, Daniel Huber, Lauren M. Weiss, Leslie A. Rogers, Diana Valencia, Mykhaylo Plotnykov, Kimberly Paragas, Renyu Hu, Te Han, Erik A. Petigura, Ryan Rubenzahl, David R. Ciardi, Aaron Householder, Gregory J. Gilbert, J. M. Joel Ong, Jingwen Zhang, Jacob Luhn, Luke Handley, Corey Beard, Steven Giacalone, Rae Holcomb, Judah Van Zandt, Ashley D. Baker, Max Brodheim, Matt Brown, David Charbonneau, Karen A. Collins, Ian J. M. Crossfield, William Deich, Xavier Dumusque, Steven R. Gibson, Emily Gilbert, Grant M. Hill, Bradford Holden, Jon M. Jenkins, Stephen Kaye, Russ R. Laher, Kyle Lanclos, W. Garett Levine, Joel Payne, Alex S. Polanski, John O’Meara, George R. Ricker, Kodi Rider, Paul Robertson, Arpita Roy, Joshua E. Schlieder, Christian Sc..","doi":"10.3847/2041-8213/adadd7","DOIUrl":"https://doi.org/10.3847/2041-8213/adadd7","url":null,"abstract":"We report the confirmation of TOI-6324 b, an Earth-sized (1.059 ± 0.041 R⊕) ultra-short-period (USP) planet orbiting a nearby (∼20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 ± 0.22 M⊕. Because of its extremely short orbit of just ∼6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27% ± 37%) consistent with that of Earth (∼33%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, day–night temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 ± 28 ppm.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143841315","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}
De-Chao Song, Marie Dominique, Ivan Zimovets, Qiao Li, Ying Li, Fu Yu, Yang Su, B. A. Nizamov, Ya Wang, Andrea Francesco Battaglia, Jun Tian, Li Feng, Hui Li and W. Q. Gan
{"title":"Unveiling Spatiotemporal Properties of the Quasiperiodic Pulsations in the Balmer Continuum at 3600 Å in an X-class Solar White-light Flare","authors":"De-Chao Song, Marie Dominique, Ivan Zimovets, Qiao Li, Ying Li, Fu Yu, Yang Su, B. A. Nizamov, Ya Wang, Andrea Francesco Battaglia, Jun Tian, Li Feng, Hui Li and W. Q. Gan","doi":"10.3847/2041-8213/adc4e9","DOIUrl":"https://doi.org/10.3847/2041-8213/adc4e9","url":null,"abstract":"Quasiperiodic pulsations (QPPs) in the Balmer continuum of solar white-light flares (WLFs) are rarely reported, and accurately pinpointing the spatial source of flaring QPPs remains a significant challenge. We present spatiotemporal characteristics of QPPs of an X2.8 two-ribbon solar WLF (SOL2023-12-14T17:02), which was well observed by the White-light Solar Telescope (WST) on board the Advanced Space-based Solar Observatory, with high-cadence imaging (1–2 s) in the Balmer continuum at 3600 Å. Combined with additional multi-instrument data, we find that the enhancement of the WLF in both Balmer and Paschen continua shows strong spatiotemporal correlation with hard X-ray (HXR) emissions. Notably, the pulses in the WST Balmer continuum exhibited a near-zero time lag with most HXR pulses, whereas soft X-ray and extreme ultraviolet emissions showed a lag of 2–3 s. Interestingly, quasi-harmonic QPPs with periods of ∼11 and ∼20 s were observed in multiple wavelengths in the rising phase of the white-light continuum. Furthermore, we employed Fourier transform to spatially locate the QPPs around 11 and 20 s, revealing that they primarily originated from the east flare ribbon, which exhibited the most substantial continuum enhancement. More interestingly, we find that the west ribbon contributed significantly to the 11 s QPP but had a weaker contribution to the 20 s QPP. Moreover, the occurrence of quasi-harmonic QPPs is temporally coincident with the rapid elongation and separation motions of flare ribbons. Possible mechanisms for the quasi-harmonic QPPs have been discussed. These observations provide valuable insights into QPP modeling for solar and stellar flares.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143841317","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}
Haojie Hu, Kohei Inayoshi, Zoltán Haiman, Luis C. Ho and Ken Ohsuga
{"title":"The Convergence of Heavy and Light Seeds to Overmassive Black Holes at Cosmic Dawn","authors":"Haojie Hu, Kohei Inayoshi, Zoltán Haiman, Luis C. Ho and Ken Ohsuga","doi":"10.3847/2041-8213/adc680","DOIUrl":"https://doi.org/10.3847/2041-8213/adc680","url":null,"abstract":"The James Webb Space Telescope has revealed low-luminosity active galactic nuclei at redshifts of z ≳ 4–7, many of which host accreting massive black holes (BHs) with BH-to-galaxy mass (MBH/M⋆) ratios exceeding the local values by more than an order of magnitude. The origin of these overmassive BHs remains unclear but requires potential contributions from heavy seeds and/or episodes of super-Eddington accretion. We present a growth model coupled with dark matter halo assembly to explore the evolution of the MBH/M⋆ ratio under different seeding and feedback scenarios. Given the gas inflow rates in protogalaxies, BHs grow episodically at moderate super-Eddington rates, and the mass ratio increases early on, despite significant mass loss through feedback. Regardless of seeding mechanisms, the mass ratio converges to a universal value ∼0.1–0.3, set by the balance between gas feeding and star formation efficiency in the nucleus. This behavior defines an attractor in the MBH–M⋆ diagram, where overmassive BHs grow more slowly than their hosts, while undermassive seeds experience rapid growth before aligning with the attractor. We derive an analytical expression for the universal mass ratio, linking it to feedback strength and halo growth. The convergence of evolutionary tracks erases seeding information from the mass ratio by z ∼ 4–6. Detecting BHs with ∼105−6M⊙ at higher redshifts that deviate from the convergence trend would provide key diagnostics of their birth conditions.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143832469","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}
Joheen Chakraborty, Erin Kara, Riccardo Arcodia, Johannes Buchner, Margherita Giustini, Lorena Hernández-García, Itai Linial, Megan Masterson, Giovanni Miniutti, Andrew Mummery, Christos Panagiotou, Erwan Quintin and Paula Sánchez-Sáez
{"title":"Discovery of Quasiperiodic Eruptions in the Tidal Disruption Event and Extreme Coronal Line Emitter AT2022upj: Implications for the QPE/TDE Fraction and a Connection to ECLEs","authors":"Joheen Chakraborty, Erin Kara, Riccardo Arcodia, Johannes Buchner, Margherita Giustini, Lorena Hernández-García, Itai Linial, Megan Masterson, Giovanni Miniutti, Andrew Mummery, Christos Panagiotou, Erwan Quintin and Paula Sánchez-Sáez","doi":"10.3847/2041-8213/adc2f8","DOIUrl":"https://doi.org/10.3847/2041-8213/adc2f8","url":null,"abstract":"Quasiperiodic eruptions (QPEs) are recurring soft X-ray transients emerging from the vicinity of supermassive black holes in nearby, low-mass galaxy nuclei; about 10 QPE hosts have been identified thus far. Here we report the NICER discovery of QPEs in the optically selected tidal disruption event (TDE) and extreme coronal line emitter (ECLE) AT2022upj, exhibiting a large spread in recurrence times from 0.5–3.5 days, durations from 0.3–1 days, peak luminosities from 1042.5−43.0 erg s−1, and erratic flare profiles. A wealth of evidence now links at least some QPEs to the newly formed accretion flows emerging from TDEs; AT2022upj is the third QPE reported in an optically discovered TDE. Marginalizing over the uncertain distributions of QPE peak luminosity, recurrence time, delay after TDE peak, and lifetime, we use the burgeoning sample to make a Bayesian estimate that the fraction of optical TDEs resulting in QPEs within 5 yr post-disruption is %. Along with AT2019qiz, AT2022upj also marks the second of the three optical TDE+X-ray QPEs showing coronal line emission, suggesting ECLEs may represent a subset of TDEs particularly efficient at forming QPEs and/or that sustained QPE X-ray emission contributes to coronal line emission in some galactic nuclei.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836990","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}
{"title":"Angular Momentum Transport by Internal Gravity Waves across Age","authors":"T. M. Rogers and R. P. Ratnasingam","doi":"10.3847/2041-8213/adc45a","DOIUrl":"https://doi.org/10.3847/2041-8213/adc45a","url":null,"abstract":"We present 2D numerical simulations of convection and waves in a 7M⊙ star across stellar ages ranging from zero age to terminal age main sequence. We show that waves efficiently transport angular momentum across the stellar radiative envelope at young ages. However, as the core recedes, leaving behind a “spike” in the Brunt–Väisälä frequency at the convective–radiative interface, the waves are severely attenuated. This, coupled with the changing stratification throughout the radiation zone, leads to significantly reduced angular momentum transport at later stages on the main sequence. Indeed the angular momentum transport at mid–main sequence is typically 3–4 orders of magnitude lower than at zero age, though we expect this to be somewhat mitigated by the chemical mixing also induced by such waves. We provide measures of the angular momentum transport, both in terms of the divergence of the Reynolds stress and a typical “wave luminosity.” However, we caution that the angular momentum transport drives shear flows, resulting in both slowing and speeding up of radiative interiors. While the values of Reynolds stress and angular momentum transport are only within the context of these limited simulations, they are not significantly different to those found previously using simpler prescriptions, providing some confidence in their applicability.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836994","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}
{"title":"A Neutron Capture Explanation for the 10 MeV Emission Line Seen in GRB 221009A","authors":"Jiahuan Zhu, Hua Feng and Tong Liu","doi":"10.3847/2041-8213/adc73a","DOIUrl":"https://doi.org/10.3847/2041-8213/adc73a","url":null,"abstract":"The brightest ever gamma-ray burst (GRB) 221009A displays a significant emission line component around 10 MeV. As the GRB central engine is neutron rich, we propose that the emission line could be originally due to the 2.223 MeV gamma rays following neutron capture with protons. The measured line profile can be adequately fitted with a neutron capture model that involves thermal broadening and a bulk Doppler shift. The spectral modeling reveals a Doppler factor varying from 5.1 to 2.1 for the neutron-rich component, along with a temperature increase from 300 keV to about 900 keV, during the time interval of 280–360 s since the trigger, with about 10−2 M⊙ deuteriums produced in the process. We argue that the neutron capture can take place in the outer shell of a structured jet, and the disk wind could be another possible site.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827738","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}
{"title":"A Constraint on Superheavy Elements of the GRB–Kilonova AT 2023vfi","authors":"Zhengyan Liu, Ji-an Jiang and Wen Zhao","doi":"10.3847/2041-8213/adc260","DOIUrl":"https://doi.org/10.3847/2041-8213/adc260","url":null,"abstract":"The discovery of the kilonova (KN) AT 2017gfo, accompanying the gravitational wave event GW170817, provides crucial insight into the synthesis of heavy elements during binary neutron star (BNS) mergers. Following this landmark event, another KN was detected in association with the second-brightest gamma-ray burst (GRB) observed to date, GRB 230307A, and subsequently confirmed by observations of the James Webb Space Telescope (JWST). In this work, we conduct an end-to-end simulation to analyze the temporal evolution of the KN AT 2023vfi associated with GRB 230307A and constrain the abundances of superheavy elements produced. We find that the temporal evolution of AT 2023vfi is similar to AT 2017gfo in the first week post-burst. Additionally, the r-process nuclide abundances of lanthanide-rich ejecta, derived from numerical relativity simulations of BNS mergers, can also successfully interpret the temporal evolution of the KN with the lanthanide-rich ejecta mass of 0.02M⊙, which is consistent with the mass range of dynamical ejecta from numerical simulations in the literature. Both findings strongly suggest the hypothesis that GRB 230307A originated from a BNS merger, similar to AT 2017gfo. Based on the first-time observation of the KN for JWST, we are able to constrain the superheavy elements of another KN following AT 2017gfo. The pre-radioactive-decay abundances of the superheavy nuclides 222Rn, 223Ra, 224Ra, and 225Ac are estimated to be at least on the order of 1 × 10−5. These abundance estimates provide valuable insight into the synthesis of superheavy elements in BNS mergers, contributing to our understanding of astrophysical r-process nucleosynthesis.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827739","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}
Michael J. Rutkowski, Bonnabelle Zabelle, Tyler Hagen, Anahita Alavi, Seth Cohen, Christopher Conselice, Norman Grogin, Yicheng Guo, Matthew Hayes, Sugata Kaviraj, Anton Koekemoer, Ray A. Lucas, Kameswara Bharadwaj Mantha, Alec Martin, Vihang Mehta, Bahram Mobasher, Nimish Hathi, Zhiyuan Ji, Kalina V. Nedkova, Robert O’Connell, Marc Rafelski, Claudia Scarlata, Harry I. Teplitz, Xin Wang, Rogier Windhorst, L. Y. Aaron Yung and
{"title":"Recent Star Formation in 0.5 < z < 1.5 Quiescent Galaxies","authors":"Michael J. Rutkowski, Bonnabelle Zabelle, Tyler Hagen, Anahita Alavi, Seth Cohen, Christopher Conselice, Norman Grogin, Yicheng Guo, Matthew Hayes, Sugata Kaviraj, Anton Koekemoer, Ray A. Lucas, Kameswara Bharadwaj Mantha, Alec Martin, Vihang Mehta, Bahram Mobasher, Nimish Hathi, Zhiyuan Ji, Kalina V. Nedkova, Robert O’Connell, Marc Rafelski, Claudia Scarlata, Harry I. Teplitz, Xin Wang, Rogier Windhorst, L. Y. Aaron Yung and","doi":"10.3847/2041-8213/adbe7c","DOIUrl":"https://doi.org/10.3847/2041-8213/adbe7c","url":null,"abstract":"Observations of massive, quiescent galaxies reveal a relatively uniform evolution: following prolific star formation in the early Universe, these galaxies quench and transition to their characteristic quiescent state in the local Universe. The debate on the relative role and frequency of the process(es) driving this evolution is robust. In this Letter, we identify 0.5 ≲ z ≲ 1.5 massive, quiescent galaxies in the Hubble Space Telescope/UVCANDELS extragalactic deep fields using traditional color selection methods and model their spectral energy distributions, incorporating novel UV images. This analysis reveals ∼15% of massive, quiescent galaxies have experienced minor, recent star formation (<10% of total stellar mass within the past ∼1 Gyr). We find only a marginal, positive correlation between the probability for recent star formation and a measure of the richness of the local environment from a statistical analysis. Assuming the recent star formation present in these quiescent galaxies is physically linked to the local environment, these results suggest only a minor role for dynamic external processes (galaxy mergers and interactions) in the formation and evolution of these galaxies at this redshift.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143832437","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}
{"title":"Effects of Ion Temperature Anisotropy on Ion-scale Waves’ Generation in the Near-Sun Solar Wind: Parker Solar Probe Observations","authors":"Wen Liu, Huan-Yu Jia and Si-Ming Liu","doi":"10.3847/2041-8213/adbdcc","DOIUrl":"https://doi.org/10.3847/2041-8213/adbdcc","url":null,"abstract":"The ion-scale electromagnetic waves are observed frequently within 0.3 au. Their generation and dissipation driven by wave–particle interaction are very important energy transfer processes in the weak collision corona and solar wind and may be one of the important factors driving the evolution of ion velocity distribution functions therein. In this Letter, we statistically analyze the possible effects of ion temperature anisotropy on the generation of the observed ion-scale waves within 0.3 au. The statistical results indicate that the ion-scale waves’ occurrence rate is proportional to ion temperature anisotropy. Moreover, the high occurrence rate of left-handed (LH) waves is closely related to EMIC and firehose instabilities driven by ion temperature anisotropy. However, we only find the close connection between right-handed (RH) waves’ high occurrence rate with the proton firehose instability. Besides, for LH waves in the regions with Tp⊥/Tp∥ > 1, their high occurrence rate is usually accompanied by the higher ion temperature (Tp, Tα), larger ion temperature ratio (Tα/Tp), and weaker collision effect. The RH waves are usually accompanied by a relatively lower ion temperature, smaller ion temperature ratio, and stronger collision effect than the LH waves. This Letter suggests that the ion temperature anisotropy is one of the important energy sources for generating ion-scale waves within 0.3 au.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827737","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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