The Astrophysical Journal Letters最新文献

{"title":"Obliquity Constraints for the Extremely Eccentric Sub-Saturn Kepler-1656 b","authors":"Ryan A. Rubenzahl, Andrew W. Howard, Samuel Halverson, Cristobal Petrovich, Isabel Angelo, Guđmundur Stefánsson, Fei Dai, Aaron Householder, Benjamin Fulton, Steven R. Gibson, Arpita Roy, Abby P. Shaum, Howard Isaacson, Max Brodheim, William Deich, Grant M. Hill, Bradford Holden, Daniel Huber, Russ R. Laher, Kyle Lanclos, Joel N. Payne, Erik A. Petigura, Christian Schwab, Josh Walawender, Sharon X. Wang, Lauren M. Weiss, Joshua N. Winn and Jason T. Wright","doi":"10.3847/2041-8213/ad6985","DOIUrl":"https://doi.org/10.3847/2041-8213/ad6985","url":null,"abstract":"The orbits of close-in exoplanets provide clues to their formation and evolutionary history. Many close-in exoplanets likely formed far out in their protoplanetary disks and migrated to their current orbits, perhaps via high-eccentricity migration (HEM), a process that can also excite obliquities. A handful of known exoplanets are perhaps caught in the act of HEM, as they are observed on highly eccentric orbits with tidal circularization timescales shorter than their ages. One such exoplanet is Kepler-1656 b, which is also the only known nongiant exoplanet (<100 M⊕) with an extreme eccentricity (e = 0.84). We measured the sky-projected obliquity of Kepler-1656 b by observing the Rossiter–McLaughlin effect during a transit with the Keck Planet Finder. Our data are consistent with an aligned orbit but are also consistent with moderate misalignment with λ < 50° at 95% confidence, with the most likely solution of deg. A low obliquity would be an unlikely outcome of most eccentricity-exciting scenarios, but we show that the properties of the outer companion in the system are consistent with the coplanar HEM mechanism. Alternatively, if the system is not relatively coplanar (≲20° mutual inclination), Kepler-1656 b may be presently at a rare snapshot of long-lived eccentricity oscillations that do not induce migration. Kepler-1656 b is only the fourth exoplanet with e > 0.8 to have its obliquity constrained; expanding this population will help establish the degree to which orbital misalignment accompanies migration. Future work that constrains the mutual inclinations of outer perturbers will be key for distinguishing plausible mechanisms.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141986377","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":"Coexistence of Antisunward and Sunward Ion Cyclotron Waves in the Near-Sun Solar Wind: Excitation by the Proton Cyclotron Instability","authors":"Chen Shi, Jinsong Zhao, Si Liu, Fuliang Xiao, Yifan Wu, Trevor A. Bowen, Roberto Livi and S. D. Bale","doi":"10.3847/2041-8213/ad68fb","DOIUrl":"https://doi.org/10.3847/2041-8213/ad68fb","url":null,"abstract":"Based on observations from the Parker Solar Probe in the near-Sun solar wind, this study identifies an ion-scale wave event characterized by two distinct frequency bands. The lower-band waves exhibit right-hand polarization, while the upper-band waves have left-hand polarization. Alongside these waves, there are clear indications of the existence of both proton core and beam components, with the perpendicular temperature being higher than the parallel temperature in the measured proton velocity distribution functions (VDFs). Utilizing the plasma parameters derived from typical proton VDFs, instability analyses are conducted to investigate the mode nature of the observed waves and their excitation mechanism. The lower-band waves are identified as sunward ion cyclotron waves (ICWs), generated through the proton beam cyclotron instability; the upper-band waves are recognized as antisunward ICWs, induced by the proton core cyclotron instability. This study provides the first direct observational evidence confirming the presence of counterpropagating ICWs and proton cyclotron instability in the solar wind.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141986376","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":"Big Galaxies and Big Black Holes: The Massive Ends of the Local Stellar and Black Hole Mass Functions and the Implications for Nanohertz Gravitational Waves","authors":"Emily R. Liepold and Chung-Pei Ma","doi":"10.3847/2041-8213/ad66b8","DOIUrl":"https://doi.org/10.3847/2041-8213/ad66b8","url":null,"abstract":"We construct the z = 0 galaxy stellar mass function (GSMF) by combining the GSMF at stellar masses M* ≲ 1011.3M⊙ from the census study of Leja et al. and the GSMF of massive galaxies at M* ≳ 1011.5M⊙ from the volume-limited MASSIVE galaxy survey. To obtain a robust estimate of M* for local massive galaxies, we use MASSIVE galaxies with M* measured from detailed dynamical modeling or stellar population synthesis modeling (incorporating a bottom-heavy initial mass function) with high-quality spatially resolved spectroscopy. These two independent sets of M* agree to within ∼7%. Our new z = 0 GSMF has a higher amplitude at M* ≳ 1011.5M⊙ than previous studies, alleviating prior concerns of a lack of mass growth in massive galaxies between z ∼ 1 and 0. We derive a local black hole mass function (BHMF) from this GSMF and the scaling relation of supermassive black holes (SMBHs) and galaxy masses. The inferred abundance of local SMBHs above ∼1010M⊙ is consistent with the number of currently known systems. The predicted amplitude of the nanohertz stochastic gravitational-wave background is also consistent with the levels reported by Pulsar Timing Array teams. Our z = 0 GSMF therefore leads to concordant results in the high-mass regime of the local galaxy and SMBH populations and the gravitational-wave amplitude from merging SMBHs. An exception is that our BHMF yields a z = 0 SMBH mass density that is notably higher than the value estimated from quasars at higher redshifts.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141980898","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":"Metal-poor Stars in the MW Disk: Resonant Cooling of Vertical Oscillations of Halo Stars in Barred Galaxies","authors":"Xingchen Li, Isaac Shlosman, Daniel Pfenniger and Clayton Heller","doi":"10.3847/2041-8213/ad67d6","DOIUrl":"https://doi.org/10.3847/2041-8213/ad67d6","url":null,"abstract":"Using numerical simulations of a barred disk galaxy embedded in nonspinning and spinning dark matter (DM) halos, we present a novel mechanism of “cooling” the vertical oscillations of DM particles, which acquire disk kinematics. The underlying mechanism consists of resonant interactions between halo particles and the stellar bar, facilitated by a chaotic phase space of the system. The cooling mechanism acts both on dynamical and secular timescales, from ∼0.5 Gyr to a few Gyr. The stellar bar acts to absorb the kinetic energy of the vertical motions. Using a Milky Way (MW)–type stellar halo, we estimate the population of metal-poor disk stars trapped by the MW disk and analyze its kinematics. We find that the population of metal-poor MW disk stars with ∣z∣ ≲ 3 kpc detected by the Gaia DR3 and other surveys can have their origin in the stellar halo. The cooled population also migrates radially outwards by exchanging energy and angular momentum with the spinning bar, and prograde-moving stars have a different distribution from retrograde ones. Next, we calculated the ratio of the prograde-to-retrograde orbits of the cooled population and found that this ratio varies radially, with the fast-spinning stellar halo resulting in the shallower radial increase of this ratio outside of the corotation. The nonspinning stellar halo shows a monotonic increase of this ratio with radius outside the corotation. Together with the analyzed radial migration of these halo stars, the cooling phenomenon of halo metal-poor stars can explain their current disk population and has corollaries for the chemical evolution of disk galaxies in general.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141980901","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":"An Hi-absorption-selected Cold Rotating Disk Galaxy at z ≈ 2.193","authors":"B. Kaur, N. Kanekar, M. Neeleman, M. Rafelski, J. X. Prochaska and R. Dutta","doi":"10.3847/2041-8213/ad65fe","DOIUrl":"https://doi.org/10.3847/2041-8213/ad65fe","url":null,"abstract":"We have used the Atacama Large Millimeter/submillimeter Array to map CO(3–2) emission from a galaxy, DLA-B1228g, associated with the high-metallicity damped Lyα absorber at z ≈ 2.1929 toward the QSO PKS B1228–113. At an angular resolution of ≈0.″32 × 0.″24, DLA-B1228g shows extended CO(3–2) emission with a deconvolved size of ≈0.″78 × 0.″18, i.e., a spatial extent of ≈6.4 kpc. We detect extended stellar emission from DLA-B1228g in a Hubble Space Telescope Wide Field Camera 3 F160W image and find that Hα emission is detected in a Very Large Telescope SINFONI image from only one side of the galaxy. While the clumpy nature of the F160W emission and the offset between the kinematic and physical centers of the CO(3–2) emission are consistent with a merger scenario, this appears unlikely due to the lack of strong Hα emission, the symmetric double-peaked CO(3–2) line profile, the high molecular gas depletion timescale, and the similar velocity dispersions in the two halves of the CO(3–2) image. Kinematic modeling reveals that the CO(3–2) emission is consistent with arising from an axisymmetric rotating disk with an exponential profile, a rotation velocity of vrot = 328 ± 7 km s−1, and a velocity dispersion of σv = 62 ± 7 km s−1. The high value of the ratio vrot/σv, ≈5.3, implies that DLA-B1228g is a rotation-dominated cold disk galaxy, the second case of a high-z Hi-absorption-selected galaxy identified with a cold rotating disk. We obtain a dynamical mass of Mdyn = (1.5 ± 0.1) × 1011M⊙, similar to the molecular gas mass of ≈1011M⊙ inferred from earlier CO(1–0) studies; this implies that the galaxy is baryon-dominated in its inner regions.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141980899","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":"Observation of a Fully-formed Forward–Reverse Shock Pair due to the Interaction between Two Coronal Mass Ejections at 0.5 au","authors":"Domenico Trotta, Andrew P. Dimmock, Xochitl Blanco-Cano, Robert J. Forsyth, Heli Hietala, Naïs Fargette, Andrea Larosa, Noé Lugaz, Erika Palmerio, Simon W. Good, Juska E. Soljento, Emilia K. J. Kilpua, Emiliya Yordanova, Oreste Pezzi, Georgios Nicolaou, Timothy S. Horbury, Rami Vainio, Nina Dresing, Christopher J. Owen and Robert F. Wimmer-Schweingruber","doi":"10.3847/2041-8213/ad68fa","DOIUrl":"https://doi.org/10.3847/2041-8213/ad68fa","url":null,"abstract":"We report direct observations of a fast magnetosonic forward–reverse shock pair observed by Solar Orbiter on 2022 March 8 at the short heliocentric distance of 0.5 au. The structure, sharing some features with fully-formed stream interaction regions, is due to the interaction between two successive coronal mass ejections (CMEs), never previously observed to give rise to a forward–reverse shock pair. The scenario is supported by remote observations from extreme ultraviolet cameras and coronagraphs, where two candidate eruptions compatible with the in situ signatures have been found. In the interaction region, we find enhanced energetic particle activity, strong nonradial flow deflections, and evidence of magnetic reconnection. At 1 au, well radially aligned Wind observations reveal a complex event, with characteristic observational signatures of both stream interaction region and CME–CME interaction, thus demonstrating the importance of investigating the complex dynamics governing solar eruptive phenomena.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141980902","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":"Discovery of an Apparent Red, High-velocity Type Ia Supernova at z = 2.9 with JWST","authors":"J. D. R. Pierel, M. Engesser, D. A. Coulter, C. DeCoursey, M. R. Siebert, A. Rest, E. Egami, W. Chen, O. D. Fox, D. O. Jones, B. A. Joshi, T. J. Moriya, Y. Zenati, A. J. Bunker, P. A. Cargile, M. Curti, D. J. Eisenstein, S. Gezari, S. Gomez, M. Guolo, B. D. Johnson, M. Karmen, R. Maiolino, R. M. Quimby, B. Robertson, M. Shahbandeh, L. G. Strolger, F. Sun, Q. Wang and T. Wevers","doi":"10.3847/2041-8213/ad6908","DOIUrl":"https://doi.org/10.3847/2041-8213/ad6908","url":null,"abstract":"We present the James Webb Space Telescope (JWST) discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS+53.13485−27.82088 with a host spectroscopic redshift of 2.903 ± 0.007. The transient was identified in deep (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic follow-up with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (c ∼ 0.9) despite a host galaxy with low extinction and has a high Ca ii velocity (19,000 ± 2000 km s−1) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-z Ca-rich population. Although such an object is too red for any low-z cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (≲1σ) with ΛCDM. Therefore unlike low-z Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high z truly diverge from their low-z counterparts and to confirm that standardized luminosities nevertheless remain constant with redshift.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141980903","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":"Corvus A: A Low-mass, Isolated Galaxy at 3.5 Mpc","authors":"Michael G. Jones, David J. Sand, Burçin Mutlu-Pakdil, Catherine E. Fielder, Denija Crnojević, Paul Bennet, Kristine Spekkens, Richard Donnerstein, Amandine Doliva-Dolinsky, Ananthan Karunakaran, Jay Strader and Dennis Zaritsky","doi":"10.3847/2041-8213/ad676e","DOIUrl":"https://doi.org/10.3847/2041-8213/ad676e","url":null,"abstract":"We report the discovery of Corvus A, a low-mass, gas-rich galaxy at a distance of approximately 3.5 Mpc, identified in DR10 of the Dark Energy Camera Legacy Imaging Survey during the initial phase of our ongoing SEmi-Automated Machine LEarning Search for Semi-resolved galaxies (SEAMLESS). Jansky Very Large Array observations of Corvus A detect H i line emission at a radial velocity of 523 ± 2 km s−1. Magellan/Megacam imaging reveals an irregular and complex stellar population with both young and old stars. We detect UV emission in Neil Gehrels Swift observations, indicative of recent star formation. However, there are no signs of H ii regions in Hα imaging from Steward Observatory’s Kuiper telescope. Based on the Megacam color–magnitude diagram we measure the distance to Corvus A via the tip of the red giant branch standard candle as 3.48 ± 0.24 Mpc. This makes Corvus A remarkably isolated, with no known galaxy within ∼1 Mpc. Based on this distance, we estimate the H i and stellar mass of Corvus A to be and , respectively. Although there are some signs of rotation, the H i distribution of Corvus A appears to be close to face on, analogous to that of Leo T, and we therefore do not attempt to infer a dynamical mass from its H i line width. Higher-resolution synthesis imaging is required to confirm this morphology and to draw robust conclusions from its gas kinematics.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141980900","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":"Fragmentation in Gravitationally Unstable Collapsar Disks and Subsolar Neutron Star Mergers","authors":"Brian D. Metzger, Lam Hui and Matteo Cantiello","doi":"10.3847/2041-8213/ad6990","DOIUrl":"https://doi.org/10.3847/2041-8213/ad6990","url":null,"abstract":"Although stable neutron stars (NSs) can in principle exist down to masses Mns ≈ 0.1 M⊙, standard models of stellar core-collapse predict a robust lower limit Mns ≳ 1.2 M⊙, roughly commensurate with the Chandrasekhar mass MCh of the progenitor’s iron core (electron fraction Ye ≈ 0.5). However, this limit may be circumvented in sufficiently dense neutron-rich environments (Ye < 0.5) for which is reduced to ≲1 M⊙. Such physical conditions could arise in the black hole accretion disks formed from the collapse of rapidly rotating stars (“collapsars”), as a result of gravitational instabilities and cooling-induced fragmentation, similar to models for planet formation in protostellar disks. We confirm that the conditions to form subsolar-mass NS (ssNS) may be marginally satisfied in the outer regions of massive neutrino-cooled collapsar disks. If the disk fragments into multiple ssNSs, their subsequent coalescence offers a channel for precipitating subsolar mass LIGO/Virgo gravitational-wave mergers that does not implicate primordial black holes. The model makes several additional predictions: (1) ∼Hz frequency Doppler modulation of the ssNS-merger gravitational-wave signals due to the binary’s orbital motion in the disk; (2) at least one additional gravitational-wave event (coincident within ≲hours), from the coalescence of the ssNS-merger remnant(s) with the central black hole; (3) an associated gamma-ray burst and supernova counterpart, the latter boosted in energy and enriched with r-process elements from the NS merger(s) embedded within the exploding stellar envelope (“kilonovae inside a supernova”).","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141973766","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":"TOI-1408: Discovery and Photodynamical Modeling of a Small Inner Companion to a Hot Jupiter Revealed by Transit Timing Variations","authors":"Judith Korth, Priyanka Chaturvedi, Hannu Parviainen, Ilaria Carleo, Michael Endl, Eike W. Guenther, Grzegorz Nowak, Carina M. Persson, Phillip J. MacQueen, Alexander J. Mustill, Juan Cabrera, William D. Cochran, Jorge Lillo-Box, David Hobbs, Felipe Murgas, Michael Greklek-McKeon, Hanna Kellermann, Guillaume Hébrard, Akihiko Fukui, Enric Pallé, Jon M. Jenkins, Joseph D. Twicken, Karen A. Collins, Samuel N. Quinn, Ján Šubjak, Paul G. Beck, Davide Gandolfi, Savita Mathur, Hans J. Deeg, David W. Latham, Simon Albrecht, David Barrado, Isabelle Boisse, Hervé Bouy, Xavier Delfosse, Olivier Demangeon, Rafael A. García, Artie P. Hatzes, Neda Heidari, Kai Ikuta, Petr Kabáth, Heather A. Knutson, John Livingston, Eder Martioli, María Morales-Calderón, Giuseppe Morello, Norio Narita, Jaume Orell-Miquel, Hanna L. M. Osborne, Dinil B. Palakkatharappil, Viktoria Pinter, Seth Redfield, Howard M. Relles, Richard P. Schwarz, Sara Seager, Avi Shporer, Marek Skarka, Gregor Srdoc, Monika Stangret,..","doi":"10.3847/2041-8213/ad65fd","DOIUrl":"https://doi.org/10.3847/2041-8213/ad65fd","url":null,"abstract":"We report the discovery and characterization of a small planet, TOI-1408 c, on a 2.2 day orbit located interior to a previously known hot Jupiter, TOI-1408 b (P = 4.42 days, M = 1.86 ± 0.02 MJup, R = 2.4 ± 0.5 RJup) that exhibits grazing transits. The two planets are near 2:1 period commensurability, resulting in significant transit timing variations (TTVs) for both planets and transit duration variations for the inner planet. The TTV amplitude for TOI-1408 c is 15% of the planet’s orbital period, marking the largest TTV amplitude relative to the orbital period measured to date. Photodynamical modeling of ground-based radial velocity (RV) observations and transit light curves obtained with the Transiting Exoplanet Survey Satellite and ground-based facilities leads to an inner planet radius of 2.22 ± 0.06 R⊕ and mass of 7.6 ± 0.2 M⊕ that locates the planet into the sub-Neptune regime. The proximity to the 2:1 period commensurability leads to the libration of the resonant argument of the inner planet. The RV measurements support the existence of a third body with an orbital period of several thousand days. This discovery places the system among the rare systems featuring a hot Jupiter accompanied by an inner low-mass planet.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141918954","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}