The Astrophysical Journal Letters最新文献

{"title":"Mass-dependent Radial Distribution of Single and Binary Stars in the Pleiades and Their Dynamical Implications","authors":"Rongrong Liu, Zhengyi Shao and Lu Li","doi":"10.3847/2041-8213/adbe60","DOIUrl":"https://doi.org/10.3847/2041-8213/adbe60","url":null,"abstract":"The Pleiades is a young open cluster that has not yet dynamically relaxed, making it an ideal target to observe various internal dynamical effects. By employing a well-defined sample of main-sequence (MS) cluster members, including both MS single stars and unresolved MS+MS binaries, we revisited their individual masses and mass functions and quantified the mass dependence of their radial distributions. We found that the mass function of binaries is more top-heavy than that of single stars. Significant mass segregation is observed for both single and binary populations, respectively, with more massive objects concentrated toward the cluster center. Notably, within given mass ranges, binaries are distributed more scattered than single stars, providing direct evidence for more efficient dynamical disruption of binaries in the inner region. The radial distribution of the binary fraction, expressed as the fb–R relation can be characterized by a bimodal shape, with higher fb values in both innermost and outermost regions of the cluster. The lower-mass subsample exhibits a monotonic increase in fb with radius, reflecting the impact of binary disruption. Conversely, for the higher-mass subsample, fb decreases with radius. It can be explained that these massive cluster members, which possess higher binary probabilities, have already undergone significant mass segregation. All these observational evidence and analyses related to the radial mass distribution imply that the Pleiades is currently undergoing a complicated interplay of various internal dynamical effects, of which the modulation between mass segregation and binary disruption is particularly pronounced.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702876","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":"MIRI-LRS Spectrum of a Cold Exoplanet around a White Dwarf: Water, Ammonia, and Methane Measurements","authors":"Maël Voyer, Quentin Changeat, Pierre-Olivier Lagage, Pascal Tremblin, Rens Waters, Manuel Güdel, Thomas Henning, Olivier Absil, David Barrado, Anthony Boccaletti, Jeroen Bouwman, Alain Coulais, Leen Decin, Adrian M. Glauser, John Pye, Alistair Glasse, René Gastaud, Sarah Kendrew, Polychronis Patapis, Daniel Rouan, Ewine F. van Dishoeck, Göran Östlin, Tom P. Ray and Gillian Wright","doi":"10.3847/2041-8213/adbd46","DOIUrl":"https://doi.org/10.3847/2041-8213/adbd46","url":null,"abstract":"The study of the atmosphere of exoplanets orbiting white dwarfs is a largely unexplored field. With WD 0806-661 b, we present the first deep dive into the atmospheric physics and chemistry of a cold exoplanet around a white dwarf. We observed WD 0806-661 b using JWST’s Mid-InfraRed Instrument Low-Resolution Spectrometer, covering the wavelength range from 5 to 12 μm, and the Imager, providing us with 12.8, 15, 18, and 21 μm photometric measurements. We carried the data reduction of those data sets, tackling second-order effects to ensure a reliable retrieval analysis. Using the TauREx retrieval code, we inferred the pressure–temperature structure, atmospheric chemistry, mass, and radius of the planet. The spectrum of WD 0806-661 b is shaped by molecular absorption of water, ammonia, and methane, consistent with a cold Jupiter atmosphere, allowing us to retrieve their abundances. From the mixing ratio of water, ammonia, and methane we derive C/O = 0.34 ± 0.06, , and N/O = 0.023 ± 0.004 and the ratio of detected metals as a proxy for metallicity. We also derive upper limits for the abundance of CO and CO2 (1.2 × 10−6 and 1.6 × 10−7, respectively), which were not detected by our retrieval models. While our interpretation of WD 0806-661 b’s atmosphere is mostly consistent with our theoretical understanding, some results—such as the lack of evidence for water clouds, an apparent increase in the mixing ratio of ammonia at low pressure, or the retrieved mass at odds with the supposed age—remain surprising and require follow-up observational and theoretical studies to be confirmed.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143695522","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 JWST Panchromatic Thermal Emission Spectrum of the Warm Neptune Archetype GJ 436b","authors":"Sagnick Mukherjee, Everett Schlawin, Taylor J. Bell, Jonathan J. Fortney, Thomas G. Beatty, Thomas P. Greene, Kazumasa Ohno, Matthew M. Murphy, Vivien Parmentier, Michael R. Line, Luis Welbanks, Lindsey S. Wiser and Marcia J. Rieke","doi":"10.3847/2041-8213/adba46","DOIUrl":"https://doi.org/10.3847/2041-8213/adba46","url":null,"abstract":"GJ 436b is the archetype warm Neptune exoplanet. The planet’s thermal emission spectrum was previously observed via intensive secondary eclipse campaigns with Spitzer. The atmosphere has long been interpreted to be extremely metal-rich, out of chemical equilibrium, and potentially tidally heated. We present the first panchromatic emission spectrum of GJ 436b observed with JWST’s NIRCAM (F322W2 and F444W) and MIRI (LRS) instruments between 2.4 and 11.9 μm. Surprisingly, the JWST spectrum appears significantly fainter around 3.6 μm than that implied by Spitzer photometry. The molecular absorption features in the spectrum are relatively weak, and we only find tentative evidence of CO2 absorption at 2σ. Under the assumption of a dayside blackbody, we find Tday = 662.8 ± 5.0 K, which is similar to the zero Bond albedo equilibrium temperature. We use it to obtain a 3σ upper limit on the Bond albedo of AB ≤ 0.66. To understand the spectrum, we employ 1D radiative–convective models but find that atmospheric constraints depend strongly on model assumptions. If thermochemical equilibrium is assumed, we find a cloudy metal-enriched atmosphere (metallicity ≥300× solar). We employ 1D photochemical modeling to show that the observed spectrum is also consistent with a cloud-free, relatively lower metallicity atmosphere (metallicity ≥80× solar) with a cold internal temperature (Tint ∼ 60 K). These are much lower metallicities and internal temperatures than inferences from Spitzer photometry. The low Tday and nondetection of transmission features at high spectral resolution do suggest a role for cloud opacity, but this is not definitive.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"103 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143695525","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":"FAST Discovery of a Gas-rich and Ultrafaint Dwarf Galaxy: KK153","authors":"Jin-Long Xu, Ming Zhu, Nai-Ping Yu, Chuan-Peng Zhang, Xiao-Lan Liu, Mei Ai and Peng Jiang","doi":"10.3847/2041-8213/adbe7e","DOIUrl":"https://doi.org/10.3847/2041-8213/adbe7e","url":null,"abstract":"Based on a high-sensitivity H i survey using the Five-hundred-meter Aperture Spherical radio Telescope, we identified an isolated H i cloud with a system velocity of ∼127.0 km s−1, which is associated with an optical galaxy KK153 in space. The H i gas of KK153 shows a typical disk-galaxy structure. Using the baryonic Tully–Fisher relation, we obtained that the distance to KK153 is 2.0 Mpc. Adopting this distance, we derived a stellar mass of 4.1 M⊙ and a neutral gas fraction of 0.63, implying that KK153 is a gas-rich ultrafaint dwarf galaxy in the Local Group or its outskirts. KK153 shows a cool (∼200 K) and warm (∼7400 K) two-phase neutral medium. The g − r color distribution of KK153 suggests that new stars are mostly forming in its inner disk. The dynamical mass of KK153 is 6.9 M⊙, which is about 60 times larger than its baryonic matter. Detection of such a low-mass and gas-rich halo poses a challenge to the theory of cosmic reionization.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"9 22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143695523","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":"The Miscibility of Hydrogen and Water in Planetary Atmospheres and Interiors","authors":"Akash Gupta, Lars Stixrude and Hilke E. Schlichting","doi":"10.3847/2041-8213/adb631","DOIUrl":"https://doi.org/10.3847/2041-8213/adb631","url":null,"abstract":"Many planets in the solar system and across the Galaxy have hydrogen-rich atmospheres overlying more heavy element-rich interiors with which they interact for billions of years. Atmosphere–interior interactions are thus crucial to understanding the formation and evolution of these bodies. However, this understanding is still lacking in part because the relevant pressure–temperature conditions are extreme. We conduct molecular dynamics simulations based on density functional theory to investigate how hydrogen and water interact over a wide range of pressure and temperature, encompassing the interiors of Neptune-sized and smaller planets. We determine the critical curve at which a single homogeneous phase exsolves into two separate hydrogen-rich and water-rich phases, finding good agreement with existing experimental data. We find that the temperature along the critical curve increases with increasing pressure and shows the influence of a change in fluid structure from molecular to atomic near 30 GPa and 3000 K, which may impact magnetic field generation. The internal temperatures of many exoplanets, including TOI-270 d and K2-18 b, may lie entirely above the critical curve: the envelope is expected to consist of a single homogeneous hydrogen–water fluid, which is much less susceptible to atmospheric loss as compared with a pure hydrogen envelope. As planets cool, they cross the critical curve, leading to rainout of water-rich fluid and an increase in internal luminosity. Compositions of the resulting outer, hydrogen-rich and inner, water-rich envelopes depend on age and instellation and are governed by thermodynamics. Rainout of water may be occurring in Uranus and Neptune at present.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677595","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":"Broadband γ-Ray Spectrum of Supernova Remnant Cassiopeia A","authors":"Zhen Cao, F. Aharonian, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, C. M. Cai, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, A. M. Chen, E. S. Chen, H. X. Chen, Liang Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen, S. Z. Chen, T. L. Chen, X. B. Chen, X. J. Chen, Y. Chen, N. Cheng, Y. D. Cheng, M. C. Chu, M. Y. Cui, S. W. Cui, X. H. Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, Z. G. Dai, Danzengluobu, Y. X. Diao, X. Q. Dong, K. K. Duan, J. H. Fan, Y. Z. Fan, J. Fang, J. H. Fang, K. Fang, C. F. Feng, H. Feng, L. Feng, S. H. Feng, X. T. Feng, Y. Feng, Y. L. Feng, S. Gabici, B. Gao, C. D. Gao, Q. Gao, W. Gao, W. K. Gao, M. M. Ge, T. T. Ge, L. S. Geng, G. Giacinti, G. H. Gong, Q. B. Gou, M. H. Gu, F. L. Guo, J. Guo, X. L. Guo, Y. Q. Guo, Y. Y. Guo, Y. A. Han, O. A. Hannuksela, M. Hasan, H. H. He, H. N. He, J. Y. He, X. Y. He, Y. He, S. Hern ndez-Cadena, Y. K. Hor, B. W. Hou, C. Hou, X. Hou, H. B. Hu, S. C. Hu, C. Huang, D. H. Hua..","doi":"10.3847/2041-8213/adb97c","DOIUrl":"https://doi.org/10.3847/2041-8213/adb97c","url":null,"abstract":"The core-collapse supernova remnant (SNR) Cassiopeia A (Cas A) is one of the brightest galactic radio sources with an angular radius of . Although no extension of this source has been detected in the γ-ray band, using more than 1000 days of LHAASO data above ∼0.8 TeV, we find that its spectrum is significantly softer than those obtained with Imaging Air Cherenkov Telescopes (IACTs), and its flux near ∼1 TeV is about 2 times higher. In combination with analyses of more than 16 yr of Fermi-LAT data covering 0.1 GeV–1 TeV, we find that the spectrum above 30 GeV deviates significantly from a single power law and is best described by a smoothly broken power law with a spectral index of 1.90 ± 0.15stat (3.41 ± 0.19stat) below (above) a break energy of 0.63 ± 0.21stat TeV. Given differences in the angular resolution of LHAASO-WCDA and IACTs, TeV γ-ray emission detected with LHAASO may have a significant contribution from regions surrounding the SNR illuminated by particles accelerated earlier, which, however, are treated as background by IACTs. Detailed modeling can be used to constrain the acceleration processes of TeV particles in the early stage of SNR evolution.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143666017","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":"Eccentricities of Close Stellar Binaries","authors":"Yanqin Wu, Sam Hadden, Janosz Dewberry, Kareem El-Badry and Christopher D. Matzner","doi":"10.3847/2041-8213/adb751","DOIUrl":"https://doi.org/10.3847/2041-8213/adb751","url":null,"abstract":"Orbits of stellar binaries are in general eccentric. These eccentricities encode information about their early lives. Here, we use thousands of main-sequence binaries from the Gaia DR3 catalog to reveal that binaries inward of a few astronomical units exhibit a simple Rayleigh distribution with a mode of σe ≃ 0.3. We find the same distribution for binaries from M to A spectral types, and from tens of days to thousands of days (possibly extending to tens of astronomical units). This observed distribution is most likely primordial and its invariance suggests a single universal process. One possibility is eccentricity excitation by circumbinary disks. Another, as is suggested by the Rayleigh form, is weak scattering and ejection of brown-dwarf objects. We explore this latter scenario and find that the binary eccentricities reach an equipartition value of . So to explain the observed mode, the brown dwarfs will have to be of order one-tenth the stellar masses, and be at least as abundant in the Galaxy as in the close binaries. The veracity of both proposals remains to be tested.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"1086 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143666016","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":"The JCMT BISTRO Survey: Magnetic Fields Align with Orbital Structure in the Galactic Center","authors":"Janik Karoly, Derek Ward-Thompson, Kate Pattle, Steven N. Longmore, James Di Francesco, Anthony Whitworth, Doug Johnstone, Sarah Sadavoy, Patrick M. Koch, Meng-Zhe Yang, Ray Furuya, Xing Lu, Motohide Tamura, Victor P. Debattista, David Eden, Jihye Hwang, Frédérick Poidevin, Bijas N., Szu-Ting Chen, Eun Jung Chung, Simon Coudé, Sheng-Jun Lin, Yasuo Doi, Takashi Onaka, Lapo Fanciullo, Tie Liu, Guangxing Li, Pierre Bastien, Tetsuo Hasegawa, Woojin Kwon, Shih-Ping Lai and Keping Qiu","doi":"10.3847/2041-8213/adbc67","DOIUrl":"https://doi.org/10.3847/2041-8213/adbc67","url":null,"abstract":"We present the magnetic field in the dense material of the Central Molecular Zone (CMZ) of the Milky Way, traced in 850 μm polarized dust emission as part of the James Clerk Maxwell Telescope B-fields in STar-forming Region Observations survey. We observe a highly ordered magnetic field across the CMZ between Sgr B2 and Sgr C that is strongly preferentially aligned with the orbital gas flows within the clouds of the CMZ. We find that the observed relative orientations are nonrandom at a >99% confidence level and are consistent with models in which the magnetic field vectors are aligned within 30° to the gas flows in 3D. The deviations from aligned magnetic fields are most prominent at positive Galactic longitudes, where the CMZ clouds are more massive, denser, and more actively forming stars. Our observed strongly preferentially parallel magnetic field morphology leads us to hypothesize that in the absence of star formation, the magnetic field in the CMZ is entrained in the orbital gas flows around Sgr A*, while gravitational collapse and feedback in star-forming regions can locally reorder the field. This magnetic field behavior is similar to that observed in the CMZ of the nuclear starburst galaxy NGC 253. This suggests that despite its current low star formation rate, the CMZ of the Milky Way is analogous to those of more distant, actively star-forming, galaxies.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677589","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":"Spectropolarimetry of SN 2023ixf Reveals Both Circumstellar Material and an Aspherical Helium Core","authors":"Manisha Shrestha, Sabrina DeSoto, David J. Sand, G. Grant Williams, Jennifer L. Hoffman, Paul S. Smith, Callum McCall, Justyn R. Maund, Iain A. Steele, Klaas Wiersema, Jennifer E. Andrews, Nathan Smith, Christopher Bilinski, Peter Milne, Ramya M. Anche, K. Azalee Bostroem, Griffin Hosseinzadeh, Jeniveve Pearson, Douglas C. Leonard, Brian Hsu, Yize Dong, 一泽 董, Emily Hoang, Daryl Janzen, Jacob E. Jencson, Saurabh W. Jha, M. J. Lundquist, Darshana Mehta, Nicolás Meza Retamal, Stefano Valenti, Joseph Farah, D. Andrew Howell, Curtis McCully, Megan Newsome, Estefania Padilla Gonzalez, Craig Pellegrino and Giacomo Terreran","doi":"10.3847/2041-8213/adbb63","DOIUrl":"https://doi.org/10.3847/2041-8213/adbb63","url":null,"abstract":"We present multi-epoch optical spectropolarimetric and imaging polarimetric observations of the nearby Type II supernova (SN) 2023ixf discovered in M101 at a distance of 6.85 Mpc. The first imaging polarimetric observations were taken +2.33 days (60085.08 MJD) after the explosion, while the last imaging polarimetric data points (+73.19 and +76.19 days) were acquired after the fall from the light-curve plateau. At +2.33 days there is strong evidence of circumstellar material (CSM) interaction in the spectra and the light curve. A significant level of intrinsic polarization pr = 1.02% ± 0.07% is seen during this phase, which indicates that this CSM is aspherical. We find that the polarization evolves with time toward the interstellar polarization level during the photospheric phase, which suggests that the recombination photosphere is spherically symmetric. There is a jump in polarization (pr = 0.45% ± 0.08% and pr = 0.62% ± 0.08%) at +73.19 and +76.19 days when the light curve falls from the plateau. This is a phase where polarimetric data are sensitive to nonspherical inner ejecta or a decrease in optical depth into the single-scattering regime. We also present spectropolarimetric data that reveal line (de)polarization during most of the observed epochs. In addition, at +14.50 days we see an “inverse P Cygni” profile in the H and He line polarization, which clearly indicates the presence of asymmetrically distributed material overlying the photosphere. The overall temporal evolution of the polarization is typical for Type II SNe, but the high level of polarization during the rising phase has only been observed in SN 2023ixf.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143666019","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":"Detection of [C i] Emission in Nebular Spectra of a Peculiar Type Ia Supernova 2022pul","authors":"Jialian Liu, Xiaofeng Wang, Yi Yang, Alexei V. Filippenko, Thomas G. Brink, WeiKang Zheng, Jujia Zhang, Gaici Li and Shengyu Yan","doi":"10.3847/2041-8213/adba61","DOIUrl":"https://doi.org/10.3847/2041-8213/adba61","url":null,"abstract":"SN 2022pul gains special attention due to its possible origin as a super-Chandrasekhar-mass white dwarf (WD) explosion (also called a 03fg-like Type Ia supernova), which shows prominent [O i], [Ne i], and [Ca ii] lines in its late-time spectra taken at ∼+300 days after the time of peak brightness. In this Letter, we present new optical observations of this peculiar object, extending up to over 500 days after peak brightness. In particular, in the t ∼ +515 days spectrum, we identified for the first time the presence of narrow emission from [C i] λλ9824, 9850, which appears asymmetric and quite similar to the accompanied [O i] λ6300 line in strength and profile. Based on the violent merger model that accounts well for previous observations but leaves little carbon in the center of the ejecta, this carbon line can be reproduced by increasing the degree of clumping in the ejecta and setting the carbon mass the same as that of oxygen (∼0.06 M⊙) in the innermost region (≲2000 km s−1). In principle, the central carbon could come from the secondary WD if it is ignited when hit by the shock wave of the explosion of the primary WD and explodes as a Ca-rich supernova, whereas pure deflagration of a super-Chandrasekhar-mass WD can account for such unburnt carbon more naturally.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"95 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677588","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}