Pub Date : 2025-12-12DOI: 10.3847/2041-8213/ae211f
Mark D. Gorski and Lena Murchikova
Carbon monoxide (CO) emission is a widely used tracer of molecular hydrogen (H2) in the interstellar medium, owing to its abundance, low excitation energy, and ease of detection in cold molecular environments, in contrast to H2 itself. While the CO-to-H2 conversion factor is often assumed to be constant across the disks of galaxies, deviations are observed in extreme environments such as the central molecular zone (CMZ) in galactic nuclei. Here we present the first estimate of the CO-to-H2 conversion factor on subkiloparsec scales. We calculate CO-to-H2 conversion in the Milky Way’s circumnuclear disk/ring at ∼1 pc radius around the Galactic Center black hole. We derive a conversion factor of αCO ≃ 4.5 ± 2.5 M⊙ (K km s−1 pc2)−1 or X[CO] ≃ (2.1 ± 1.1) ×1020 cm . This value is consistent with the Galactic disk but higher than the CMZ.
一氧化碳（CO）发射是星际介质中广泛使用的分子氢（H2）的示踪剂，与H2本身相比，它具有丰度高、激发能低、在寒冷的分子环境中易于检测的特点。虽然CO-to-H2的转换因子通常被认为在整个星系盘中是恒定的，但在极端环境中，如星系核的中心分子区（CMZ），可以观察到偏差。在这里，我们提出了在亚千秒差距尺度上CO-to-H2转换因子的第一个估计。我们计算了在银河系中心黑洞周围约1pc半径的环核盘/环中CO-to-H2的转化。我们推导出αCO≃4.5±2.5 M⊙(K km s−1 pc2)−1或X[CO]≃（2.1±1.1）×1020 cm的转换因子。这个值与银盘一致，但高于CMZ。
{"title":"The CO-to-H2 Conversion Factor in the Milky Way’s Central Parsec","authors":"Mark D. Gorski and Lena Murchikova","doi":"10.3847/2041-8213/ae211f","DOIUrl":"https://doi.org/10.3847/2041-8213/ae211f","url":null,"abstract":"Carbon monoxide (CO) emission is a widely used tracer of molecular hydrogen (H2) in the interstellar medium, owing to its abundance, low excitation energy, and ease of detection in cold molecular environments, in contrast to H2 itself. While the CO-to-H2 conversion factor is often assumed to be constant across the disks of galaxies, deviations are observed in extreme environments such as the central molecular zone (CMZ) in galactic nuclei. Here we present the first estimate of the CO-to-H2 conversion factor on subkiloparsec scales. We calculate CO-to-H2 conversion in the Milky Way’s circumnuclear disk/ring at ∼1 pc radius around the Galactic Center black hole. We derive a conversion factor of αCO ≃ 4.5 ± 2.5 M⊙ (K km s−1 pc2)−1 or X[CO] ≃ (2.1 ± 1.1) ×1020 cm . This value is consistent with the Galactic disk but higher than the CMZ.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145732361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-12DOI: 10.3847/2041-8213/ae2609
Annie Heinrich, Congyao Zhang, Irina Zhuravleva, Eugene Churazov, Hannah McCall, Reinout J. van Weeren and William R. Forman
Hierarchical mergers of galaxy clusters play a key role in converting gravitational energy into thermal and kinetic energy in the local Universe. Understanding this process requires the reconstruction of cluster merger geometry, with careful consideration of projection effects. With its unprecedented spectral resolution, XRISM enables the disentanglement of merging cluster components along the line of sight via X-rays for the first time. In this Letter, we focus on the massive cluster A1914, a puzzling case wherein the galaxy and dark matter (DM) distribution appear to be in tension with the X-ray morphology. We present XRISM observations of A1914 focusing on the velocity structure of the intracluster medium. The Resolve full-array spectrum requires two merging components along the line of sight, with bulk velocities offset by ∼1000 km s−1 and velocity dispersions of ∼200 km s−1. The subarray maps of flux ratios, bulk velocity, and velocity dispersion show the two components are offset and overlapping in the plane of the sky, consistent with a major (mass ratio ∼3), near line-of-sight merger with a pericenter distance of ∼200 kpc. We conclude that the two subclusters create an overlapping spiral pattern, referred to as a “yin-yang” merger. This scenario is further supported by tailored hydrodynamical simulations of the A1914 merger, demonstrating that this type of merger can broadly reproduce the observed X-ray morphology, gas temperature map, gas velocity maps, DM distribution, and galaxy velocities. This work demonstrates the power of high-resolution X-ray spectroscopy, provided by XRISM, to resolve complex cluster merger geometries.
星系团的分层合并在局部宇宙中将引力能转化为热能和动能方面起着关键作用。理解这一过程需要重建星团合并的几何形状，并仔细考虑投影效应。凭借其前所未有的光谱分辨率，XRISM首次能够通过x射线沿视线解除合并星团成分的纠缠。在这封信中，我们关注的是大质量星系团A1914，这是一个令人困惑的例子，其中星系和暗物质（DM）的分布似乎与x射线形态处于紧张状态。我们提出了聚焦于星系团内介质速度结构的A1914的XRISM观测结果。Resolve全阵列光谱需要沿瞄准线合并两个分量，体速度偏移约1000 km s - 1，速度色散约200 km s - 1。通量比、体速度和速度色散的子阵图显示，这两个分量在天空平面上是偏移和重叠的，符合一个主要的（质量比~ 3），近视距合并，近中心距离为~ 200kpc。我们得出的结论是，这两个子集群创造了一个重叠的螺旋模式，被称为“阴阳”合并。A1914合并的流体动力学模拟进一步支持了这一设想，表明这种类型的合并可以广泛地再现观测到的x射线形态、气体温度图、气体速度图、DM分布和星系速度。这项工作证明了XRISM提供的高分辨率x射线光谱学在解决复杂的星团合并几何形状方面的能力。
{"title":"A Yin-yang Galaxy Cluster Merger in A1914 Revealed by XRISM","authors":"Annie Heinrich, Congyao Zhang, Irina Zhuravleva, Eugene Churazov, Hannah McCall, Reinout J. van Weeren and William R. Forman","doi":"10.3847/2041-8213/ae2609","DOIUrl":"https://doi.org/10.3847/2041-8213/ae2609","url":null,"abstract":"Hierarchical mergers of galaxy clusters play a key role in converting gravitational energy into thermal and kinetic energy in the local Universe. Understanding this process requires the reconstruction of cluster merger geometry, with careful consideration of projection effects. With its unprecedented spectral resolution, XRISM enables the disentanglement of merging cluster components along the line of sight via X-rays for the first time. In this Letter, we focus on the massive cluster A1914, a puzzling case wherein the galaxy and dark matter (DM) distribution appear to be in tension with the X-ray morphology. We present XRISM observations of A1914 focusing on the velocity structure of the intracluster medium. The Resolve full-array spectrum requires two merging components along the line of sight, with bulk velocities offset by ∼1000 km s−1 and velocity dispersions of ∼200 km s−1. The subarray maps of flux ratios, bulk velocity, and velocity dispersion show the two components are offset and overlapping in the plane of the sky, consistent with a major (mass ratio ∼3), near line-of-sight merger with a pericenter distance of ∼200 kpc. We conclude that the two subclusters create an overlapping spiral pattern, referred to as a “yin-yang” merger. This scenario is further supported by tailored hydrodynamical simulations of the A1914 merger, demonstrating that this type of merger can broadly reproduce the observed X-ray morphology, gas temperature map, gas velocity maps, DM distribution, and galaxy velocities. This work demonstrates the power of high-resolution X-ray spectroscopy, provided by XRISM, to resolve complex cluster merger geometries.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145728762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-12DOI: 10.3847/2041-8213/ae2098
Qiao Xue, Michael Zhang, Brandon Park Coy, Madison Brady, Xuan Ji, Jacob L. Bean, Michael Radica, Andreas Seifahrt, Julian Stürmer, Rafael Luque, Ritvik Basant, Nina Brown, Tanya Das, David Kasper, Caroline Piaulet-Ghorayeb, Eliza M.-R. Kempton and Edwin Kite
We report first results from the JWST Rocky Worlds Director’s Discretionary Time program. Two secondary eclipses of the terrestrial exoplanet GJ 3929b were recently observed using MIRI photometric imaging at 15 μm. We present a reduction of these data using the updated SPARTA pipeline. We also refine the planet mass, radius, and predicted time of secondary eclipse using a new sector of TESS data and new, high-precision radial velocities from the MAROON-X spectrograph. For the two JWST observations, we recover secondary eclipse depths of 177 ppm and 143 ppm at times consistent with a nearly circular orbit, as expected from the radial velocity data. A joint fit of the two visits yields a dayside brightness temperature Tp,dayside = 782 ± 79 K for GJ 3929b, which is consistent with the maximum brightness temperature K for a bare black rock (i.e., assuming zero Bond albedo and no heat redistribution). These results rule out CO2-rich atmospheres thicker than 100 mbar at >3σ, suggesting that GJ 3929b has lost any significant secondary atmosphere. The radial velocity data also indicate two additional nontransiting planets in the system: a previously identified planet in a 15.0 days orbit and a newly identified planet candidate in a 6.1 days orbit.
{"title":"The JWST Rocky Worlds DDT Program Reveals GJ 3929b to Likely Be a Bare Rock","authors":"Qiao Xue, Michael Zhang, Brandon Park Coy, Madison Brady, Xuan Ji, Jacob L. Bean, Michael Radica, Andreas Seifahrt, Julian Stürmer, Rafael Luque, Ritvik Basant, Nina Brown, Tanya Das, David Kasper, Caroline Piaulet-Ghorayeb, Eliza M.-R. Kempton and Edwin Kite","doi":"10.3847/2041-8213/ae2098","DOIUrl":"https://doi.org/10.3847/2041-8213/ae2098","url":null,"abstract":"We report first results from the JWST Rocky Worlds Director’s Discretionary Time program. Two secondary eclipses of the terrestrial exoplanet GJ 3929b were recently observed using MIRI photometric imaging at 15 μm. We present a reduction of these data using the updated SPARTA pipeline. We also refine the planet mass, radius, and predicted time of secondary eclipse using a new sector of TESS data and new, high-precision radial velocities from the MAROON-X spectrograph. For the two JWST observations, we recover secondary eclipse depths of 177 ppm and 143 ppm at times consistent with a nearly circular orbit, as expected from the radial velocity data. A joint fit of the two visits yields a dayside brightness temperature Tp,dayside = 782 ± 79 K for GJ 3929b, which is consistent with the maximum brightness temperature K for a bare black rock (i.e., assuming zero Bond albedo and no heat redistribution). These results rule out CO2-rich atmospheres thicker than 100 mbar at >3σ, suggesting that GJ 3929b has lost any significant secondary atmosphere. The radial velocity data also indicate two additional nontransiting planets in the system: a previously identified planet in a 15.0 days orbit and a newly identified planet candidate in a 6.1 days orbit.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145728760","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}
Following its launch on 2024 January 9, the Einstein Probe (EP) telescope has detected hundreds of fast X-ray transients (FXTs), yet their physical origins remain elusive. Understanding their luminosity function and formation rate is crucial for elucidating their nature. Recently, the EP team has provided the latest catalog of EP-detected FXTs. Based on this catalog, we present a model-independent nonparametric approach to derive the luminosity function and formation rate of FXTs. Our analysis reveals significant cosmological luminosity evolution, characterized by a scaling relationship of (1 + z)3.58. After accounting for this evolution, we establish that the local luminosity function is best represented by a broken power law, with a break luminosity of (4.17 ± 0.34) × 1046 erg s−1. The formation rate exhibits a broken power law as ρ(z) ∝ (1 + z)−4.25 at z ⪅ 0.9 and ρ(z) ∝ (1 + z)−0.26 at z ⪆ 0.9, yielding a local rate of approximately Gpc−3 yr−1. This rate is higher than that of long gamma-ray bursts (LGRBs). Our findings indicate that a component of FXTs is associated with LGRBs.
{"title":"The Formation Rate and Luminosity Function of Fast X-Ray Transients from Einstein Probe","authors":"Yizhou Guo, Houdun Zeng, Junjie Wei, Hao Zhou, Zhiping Jin, Xuefeng Wu and Daming Wei","doi":"10.3847/2041-8213/ae2745","DOIUrl":"https://doi.org/10.3847/2041-8213/ae2745","url":null,"abstract":"Following its launch on 2024 January 9, the Einstein Probe (EP) telescope has detected hundreds of fast X-ray transients (FXTs), yet their physical origins remain elusive. Understanding their luminosity function and formation rate is crucial for elucidating their nature. Recently, the EP team has provided the latest catalog of EP-detected FXTs. Based on this catalog, we present a model-independent nonparametric approach to derive the luminosity function and formation rate of FXTs. Our analysis reveals significant cosmological luminosity evolution, characterized by a scaling relationship of (1 + z)3.58. After accounting for this evolution, we establish that the local luminosity function is best represented by a broken power law, with a break luminosity of (4.17 ± 0.34) × 1046 erg s−1. The formation rate exhibits a broken power law as ρ(z) ∝ (1 + z)−4.25 at z ⪅ 0.9 and ρ(z) ∝ (1 + z)−0.26 at z ⪆ 0.9, yielding a local rate of approximately Gpc−3 yr−1. This rate is higher than that of long gamma-ray bursts (LGRBs). Our findings indicate that a component of FXTs is associated with LGRBs.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"148 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145728761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-12DOI: 10.3847/2041-8213/ae1cb8
Raphael Baer-Way, Nayana A. J., Wynn Jacobson-Galán, Poonam Chandra, Maryam Modjaz, Samantha C. Wu, Daichi Tsuna, Raffaella Margutti, Ryan Chornock, Craig Pellegrino, Yize Dong, Maria R. Drout, Charles D. Kilpatrick, Dan Milisavljevic, Daniel Patnaude and Candice Stauffer
Supernovae that interact with hydrogen-poor, helium-rich circumstellar material (CSM), known as type Ibn supernovae (SNe Ibn), present a unique opportunity to probe mass-loss processes in massive stars. In this work, we report the first radio detection of an SN Ibn, SN 2023fyq, and characterize the mass-loss history of its stellar progenitor using the radio and X-ray observations obtained over 18 months post-explosion. We find that the radio emission from 58 to 185 days is best modeled by synchrotron radiation attenuated by free–free absorption from a CSM of density ∼10−18 g cm−3 (∼106ρISM) at a radius of 1016 cm, corresponding to a mass-loss rate of ∼4 × 10−3M⊙ yr−1 (for a CSM velocity of 1700 km s−1 from optical spectroscopy) from 0.7 to 3 yr before the explosion. This timescale is consistent with the time frame over which pre-explosion optical outbursts were observed. However, our late-time observations at 525 days post-explosion yield nondetections, and the 3σ upper limits (along with an X-ray nondetection) allow us to infer a drop in the progenitor mass-loss rate at 5–10 yr pre-explosion with < 2.5 × 10−3M⊙ yr−1. These results suggest a shell-like CSM from at most 4 × 1015 to 2 × 1016 cm (∼105R⊙), with a CSM density that is roughly consistent with predictions from a merger model for this object. Future radio observations of a larger sample of SNe Ibn will provide key details on the extent and density of their helium-rich CSM.
与贫氢富氦的星周物质（CSM）相互作用的超新星，被称为Ibn型超新星（SNe Ibn），为探测大质量恒星的质量损失过程提供了一个独特的机会。在这项工作中，我们报告了对SN Ibn， SN 2023fyq的首次无线电探测，并利用爆炸后18个月获得的无线电和x射线观测资料表征了其恒星祖先的质量损失历史。我们发现，58至185天的射电辐射最好用同步辐射来模拟，这种同步辐射被密度为~ 10−18 g cm−3 （~ 106ρISM）的CSM在1016 cm半径处的自由-自由吸收衰减，对应于爆炸前0.7至3年的质量损失率为~ 4 × 10−3M⊙yr−1（从光谱学上看，CSM速度为1700 km s−1）。这个时间尺度与观测到的爆炸前光学爆发的时间范围一致。然而，我们在爆炸后525天的后期观测结果没有检测到，3σ上限（以及x射线未检测到）允许我们推断在爆炸前5-10年的前体质量损失率下降，< 2.5 × 10−3M⊙yr−1。这些结果表明，一个壳状的CSM最多从4 × 1015到2 × 1016 cm (~ 105R⊙)，其CSM密度与该天体合并模型的预测大致一致。未来对SNe Ibn更大样本的无线电观测将提供关于其富含氦的CSM的范围和密度的关键细节。
{"title":"The First Radio View of a Type Ibn Supernova in SN 2023fyq: Understanding the Mass-loss History in the Last Decade before the Explosion","authors":"Raphael Baer-Way, Nayana A. J., Wynn Jacobson-Galán, Poonam Chandra, Maryam Modjaz, Samantha C. Wu, Daichi Tsuna, Raffaella Margutti, Ryan Chornock, Craig Pellegrino, Yize Dong, Maria R. Drout, Charles D. Kilpatrick, Dan Milisavljevic, Daniel Patnaude and Candice Stauffer","doi":"10.3847/2041-8213/ae1cb8","DOIUrl":"https://doi.org/10.3847/2041-8213/ae1cb8","url":null,"abstract":"Supernovae that interact with hydrogen-poor, helium-rich circumstellar material (CSM), known as type Ibn supernovae (SNe Ibn), present a unique opportunity to probe mass-loss processes in massive stars. In this work, we report the first radio detection of an SN Ibn, SN 2023fyq, and characterize the mass-loss history of its stellar progenitor using the radio and X-ray observations obtained over 18 months post-explosion. We find that the radio emission from 58 to 185 days is best modeled by synchrotron radiation attenuated by free–free absorption from a CSM of density ∼10−18 g cm−3 (∼106ρISM) at a radius of 1016 cm, corresponding to a mass-loss rate of ∼4 × 10−3M⊙ yr−1 (for a CSM velocity of 1700 km s−1 from optical spectroscopy) from 0.7 to 3 yr before the explosion. This timescale is consistent with the time frame over which pre-explosion optical outbursts were observed. However, our late-time observations at 525 days post-explosion yield nondetections, and the 3σ upper limits (along with an X-ray nondetection) allow us to infer a drop in the progenitor mass-loss rate at 5–10 yr pre-explosion with < 2.5 × 10−3M⊙ yr−1. These results suggest a shell-like CSM from at most 4 × 1015 to 2 × 1016 cm (∼105R⊙), with a CSM density that is roughly consistent with predictions from a merger model for this object. Future radio observations of a larger sample of SNe Ibn will provide key details on the extent and density of their helium-rich CSM.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"170 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145728859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-11DOI: 10.3847/2041-8213/ae16a6
Brendan O’Connor, Roberto Ricci, Eleonora Troja, Antonella Palmese, Yu-Han Yang, Geoffrey Ryan, Hendrik van Eerten, Muskan Yadav, Xander J. Hall, Ariel Amsellem, R. L. Becerra, Malte Busmann, Tomás Cabrera, Simone Dichiara, Lei Hu, Ravjit Kaur, Keerthi Kunnumkai and Ignacio Magaña Hernandez
The first joint electromagentic (EM) and gravitational-wave (GW) detection, known as GW170817, marked a critical juncture in our collective understanding of compact object mergers. However, it has now been 8 yr since this discovery, and the search for a second EM-GW detection has yielded no robust discoveries. Recently, on 2025 August 18, the LIGO–Virgo–KAGRA Collaboration reported a low-significance (high-false-alarm rate) binary neutron star merger candidate S250818k. Rapid optical follow-up revealed a single optical candidate AT2025ulz (z = 0.08484) that initially appeared consistent with kilonova emission. We quickly initiated a set of observations with Swift, XMM-Newton, Chandra, and the Very Large Array to search for nonthermal afterglow emission. Our deep X-ray and radio search rules out that the optical rebrightening of AT2025ulz is related to the afterglow onset, reinforcing its classification as a stripped-envelope supernova (SN 2025ulz). We derive constraints on the afterglow parameters for a hypothetical binary neutron star merger at the distance of AT2025ulz (≈400 Mpc) based on our X-ray and radio limits. We conclude that our observational campaign could exclude a GW170817-like afterglow out to viewing angles of θv ≈ 12 5. We briefly discuss the prospects for the future discovery of off-axis afterglows.
第一次电磁（EM）和引力波（GW）联合探测，被称为GW170817，标志着我们对紧凑物体合并的集体理解的关键时刻。然而，自从这一发现至今已经过去了8年，而寻找第二个EM-GW探测并没有产生任何有力的发现。最近，在2025年8月18日，LIGO-Virgo-KAGRA合作报告了一个低显著性（高误报率）双中子星合并候选S250818k。快速光学跟踪发现了一个单一的候选光AT2025ulz (z = 0.08484)，最初看起来与千新星发射一致。我们很快启动了一系列的观测，包括斯威夫特、xmm -牛顿、钱德拉和甚大阵列，以寻找非热余辉发射。我们的深x射线和射电搜索排除了AT2025ulz的光学再亮与余辉的开始有关，加强了它作为剥离包膜超新星（SN 2025ulz）的分类。基于x射线和射电极限，我们推导出了AT2025ulz（≈400 Mpc）距离上假设的双中子星合并的余辉参数约束。我们得出的结论是，我们的观测活动可以排除在θv≈12.5角度的gw170817类余辉。我们简要地讨论了未来发现离轴余辉的前景。
{"title":"AT2025ulz and S250818k: Deep X-Ray and Radio Limits on Off-axis Afterglow Emission and Prospects for Future Discovery","authors":"Brendan O’Connor, Roberto Ricci, Eleonora Troja, Antonella Palmese, Yu-Han Yang, Geoffrey Ryan, Hendrik van Eerten, Muskan Yadav, Xander J. Hall, Ariel Amsellem, R. L. Becerra, Malte Busmann, Tomás Cabrera, Simone Dichiara, Lei Hu, Ravjit Kaur, Keerthi Kunnumkai and Ignacio Magaña Hernandez","doi":"10.3847/2041-8213/ae16a6","DOIUrl":"https://doi.org/10.3847/2041-8213/ae16a6","url":null,"abstract":"The first joint electromagentic (EM) and gravitational-wave (GW) detection, known as GW170817, marked a critical juncture in our collective understanding of compact object mergers. However, it has now been 8 yr since this discovery, and the search for a second EM-GW detection has yielded no robust discoveries. Recently, on 2025 August 18, the LIGO–Virgo–KAGRA Collaboration reported a low-significance (high-false-alarm rate) binary neutron star merger candidate S250818k. Rapid optical follow-up revealed a single optical candidate AT2025ulz (z = 0.08484) that initially appeared consistent with kilonova emission. We quickly initiated a set of observations with Swift, XMM-Newton, Chandra, and the Very Large Array to search for nonthermal afterglow emission. Our deep X-ray and radio search rules out that the optical rebrightening of AT2025ulz is related to the afterglow onset, reinforcing its classification as a stripped-envelope supernova (SN 2025ulz). We derive constraints on the afterglow parameters for a hypothetical binary neutron star merger at the distance of AT2025ulz (≈400 Mpc) based on our X-ray and radio limits. We conclude that our observational campaign could exclude a GW170817-like afterglow out to viewing angles of θv ≈ 12 5. We briefly discuss the prospects for the future discovery of off-axis afterglows.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"242 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145717492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-11DOI: 10.3847/2041-8213/ae267c
Bin Zhuang, Tingyu Gou, Noé Lugaz, Manuela Temmer, Brian E. Wood, Yara De Leo, Shaheda Begum Shaik, Phillip Hess, Carlos R. Braga, Cecilia Mac Cormack and Xiaolei Li
Coronal mass ejections (CMEs), as seen in white-light (WL) coronagraphs, often exhibit a classic three-part structure consisting of a bright front, a dark cavity, and a bright core. With the launch of Solar Orbiter, cospatial imaging of solar eruptions in multiwavelengths of extreme-ultraviolet (EUV) and WL has become available. We present a CME that erupted on 2022 September 23, observed under a uniquely favorable viewing geometry. The CME bright core and its eruptive prominence can be cospatially observed up to a coronal height of 3.5 R⊙ in the middle corona, in WL using COR1 on board STEREO-A and in EUV using the Full Sun Imager on board Solar Orbiter. Cospatial, multiwavelength observations indicate that the CME bright core observed in WL was almost entirely composed of the prominence material, which was heated during the CME eruption. EUV emissions in 174 and 304 Å of the prominence were largely cospatial when the CME propagated to the middle corona, though subtle differences remained. We further discuss the potential temperature in the bright core region and find that the core was heated as it rose, likely reaching temperatures of about 0.1–0.8 MK.
{"title":"Cospatial Multiwavelength Observations of an Eruptive Prominence as the Bright Core of a Coronal Mass Ejection","authors":"Bin Zhuang, Tingyu Gou, Noé Lugaz, Manuela Temmer, Brian E. Wood, Yara De Leo, Shaheda Begum Shaik, Phillip Hess, Carlos R. Braga, Cecilia Mac Cormack and Xiaolei Li","doi":"10.3847/2041-8213/ae267c","DOIUrl":"https://doi.org/10.3847/2041-8213/ae267c","url":null,"abstract":"Coronal mass ejections (CMEs), as seen in white-light (WL) coronagraphs, often exhibit a classic three-part structure consisting of a bright front, a dark cavity, and a bright core. With the launch of Solar Orbiter, cospatial imaging of solar eruptions in multiwavelengths of extreme-ultraviolet (EUV) and WL has become available. We present a CME that erupted on 2022 September 23, observed under a uniquely favorable viewing geometry. The CME bright core and its eruptive prominence can be cospatially observed up to a coronal height of 3.5 R⊙ in the middle corona, in WL using COR1 on board STEREO-A and in EUV using the Full Sun Imager on board Solar Orbiter. Cospatial, multiwavelength observations indicate that the CME bright core observed in WL was almost entirely composed of the prominence material, which was heated during the CME eruption. EUV emissions in 174 and 304 Å of the prominence were largely cospatial when the CME propagated to the middle corona, though subtle differences remained. We further discuss the potential temperature in the bright core region and find that the core was heated as it rose, likely reaching temperatures of about 0.1–0.8 MK.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"141 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145717534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-11DOI: 10.3847/2041-8213/ae2007
Nathalie K. Jones, Jason J. Wang, Eric L. Nielsen, Robert J. De Rosa, Anne E. Peck, William Roberson, Jean-Baptiste Ruffio, Jerry W. Xuan, Bruce A. Macintosh, S. Mark Ammons, Vanessa P. Bailey, Travis S. Barman, Joanna Bulger, Eugene Chiang, Jeffrey K. Chilcote, Gaspard Duchêne, Thomas M. Esposito, Michael P. Fitzgerald, Katherine B. Follette, Stephen Goodsell, James R. Graham, Alexandra Z. Greenbaum, Pascale Hibon, Patrick Ingraham, Paul Kalas, Quinn M. Konopacky, Michael C. Liu, Franck Marchis, Jérôme Maire, Christian Marois, Brenda Matthews, Dimitri Mawet, Stanimir Metchev, Maxwell A. Millar-Blanchaer, Rebecca Oppenheimer, David W. Palmer, Jenny Patience, Marshall D. Perrin, Lisa Poyneer, Laurent Pueyo, Abhijith Rajan, Julien Rameau, Fredrik T. Rantakyrö, Bin Ren, Aniket Sanghi, Dmitry Savransky, Adam C. Schneider, Anand Sivaramakrishnan, Adam J. R. W. Smith, Inseok Song, Remi Soummer, Sandrine Thomas, Kimberly Ward-Duong and Schuyler G. Wolff
We present confirmation of HD 143811 AB b, a substellar companion to spectroscopic binary HD 143811 AB through direct imaging with the Gemini Planet Imager (GPI) and Keck NIRC2. HD 143811 AB was observed as a part of the GPI Exoplanet Survey in 2016 and 2019 and is a member of the Sco-Cen star formation region. The exoplanet is detected ∼430 mas from the host star by GPI. With two GPI epochs and one from Keck/NIRC2 in 2022, we confirm through common proper motion analysis that the object is bound to its host star. We derive an orbit with a semimajor axis of au and eccentricity . Spectral analysis of the GPI H-band spectrum and NIRC2 L′ photometry provides additional proof that this object is a substellar companion. We compare the spectrum of HD 143811 AB b to PHOENIX stellar models and Exo-Radioactive-Convective Equilibrium Model (REM) exoplanet atmosphere models and find that Exo-REM models provide the best fits to the data. From the Exo-REM models, we derive an effective temperature of K for the planet and translate the derived luminosity of the planet to a mass of 5.6 ± 1.1 MJup assuming hot-start evolutionary models. HD 143811 AB b is the first directly imaged planet around a binary that is not on an ultrawide orbit. Future characterization of this object will shed light on the formation of planets around binary star systems.
通过双子座行星成像仪（GPI）和凯克NIRC2的直接成像，我们证实了HD 143811 AB b，它是光谱双星HD 143811 AB的一颗伴星。HD 143811 AB是2016年和2019年GPI系外行星调查的一部分，是sco -半人马座恒星形成区的一员。这颗系外行星是由GPI探测到的，距离主星约430 mas。利用两个GPI时代和一个来自2022年Keck/NIRC2的时代，我们通过共同固有运动分析证实了该物体与它的主恒星绑定。我们推导出一个半长轴为au且偏心的轨道。GPI的h波段光谱分析和NIRC2 L的光度测定提供了额外的证据，证明这个物体是一个次恒星伴星。我们将HD 143811 AB b的光谱与PHOENIX恒星模型和exo - radiation - convection Equilibrium Model （REM）系外行星大气模型进行了比较，发现Exo-REM模型提供了最好的拟合数据。根据Exo-REM模型，我们得出了该行星的有效温度K，并将该行星的光度转换为5.6±1.1 MJup的质量，假设热启动演化模型。HD 143811 AB b是第一颗直接被成像的行星，它围绕着一颗双星，但不在超宽轨道上。对这一天体的未来特征描述将揭示双星系统周围行星的形成。
{"title":"HD 143811 AB b: A Directly Imaged Planet Orbiting a Spectroscopic Binary in Sco-Cen","authors":"Nathalie K. Jones, Jason J. Wang, Eric L. Nielsen, Robert J. De Rosa, Anne E. Peck, William Roberson, Jean-Baptiste Ruffio, Jerry W. Xuan, Bruce A. Macintosh, S. Mark Ammons, Vanessa P. Bailey, Travis S. Barman, Joanna Bulger, Eugene Chiang, Jeffrey K. Chilcote, Gaspard Duchêne, Thomas M. Esposito, Michael P. Fitzgerald, Katherine B. Follette, Stephen Goodsell, James R. Graham, Alexandra Z. Greenbaum, Pascale Hibon, Patrick Ingraham, Paul Kalas, Quinn M. Konopacky, Michael C. Liu, Franck Marchis, Jérôme Maire, Christian Marois, Brenda Matthews, Dimitri Mawet, Stanimir Metchev, Maxwell A. Millar-Blanchaer, Rebecca Oppenheimer, David W. Palmer, Jenny Patience, Marshall D. Perrin, Lisa Poyneer, Laurent Pueyo, Abhijith Rajan, Julien Rameau, Fredrik T. Rantakyrö, Bin Ren, Aniket Sanghi, Dmitry Savransky, Adam C. Schneider, Anand Sivaramakrishnan, Adam J. R. W. Smith, Inseok Song, Remi Soummer, Sandrine Thomas, Kimberly Ward-Duong and Schuyler G. Wolff","doi":"10.3847/2041-8213/ae2007","DOIUrl":"https://doi.org/10.3847/2041-8213/ae2007","url":null,"abstract":"We present confirmation of HD 143811 AB b, a substellar companion to spectroscopic binary HD 143811 AB through direct imaging with the Gemini Planet Imager (GPI) and Keck NIRC2. HD 143811 AB was observed as a part of the GPI Exoplanet Survey in 2016 and 2019 and is a member of the Sco-Cen star formation region. The exoplanet is detected ∼430 mas from the host star by GPI. With two GPI epochs and one from Keck/NIRC2 in 2022, we confirm through common proper motion analysis that the object is bound to its host star. We derive an orbit with a semimajor axis of au and eccentricity . Spectral analysis of the GPI H-band spectrum and NIRC2 L′ photometry provides additional proof that this object is a substellar companion. We compare the spectrum of HD 143811 AB b to PHOENIX stellar models and Exo-Radioactive-Convective Equilibrium Model (REM) exoplanet atmosphere models and find that Exo-REM models provide the best fits to the data. From the Exo-REM models, we derive an effective temperature of K for the planet and translate the derived luminosity of the planet to a mass of 5.6 ± 1.1 MJup assuming hot-start evolutionary models. HD 143811 AB b is the first directly imaged planet around a binary that is not on an ultrawide orbit. Future characterization of this object will shed light on the formation of planets around binary star systems.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145717493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-11DOI: 10.3847/2041-8213/ae13b1
Ricardo Yarza, Morgan MacLeod, Benjamin Idini, Ruth Murray-Clay and Enrico Ramirez-Ruiz
We model the optical and infrared transient ZTF SLRN-2020, previously associated with a star-planet merger. We consider the scenario in which orbital decay via tidal dissipation led to the merger, and we find that tidal heating within the star was likely unobservable in the archival image of the system taken 12 yr before the merger. The observed dust formation months before the merger is consistent with a planet of mass Mp ≳ 5MJ ejecting material as it skims the stellar surface. This interaction gradually intensifies, leading to significant mass ejection on a dynamical timescale (≈hours) as the planet plunges into the stellar interior. Part of the recombination transient associated with this dynamical mass ejection might be inaccessible to the optical observations because its duration (≈hours) is comparable to the cadence. Correspondingly, the observed duration of the transient (≈100 days) is inconsistent with a single episode of dynamical mass ejection. Instead, the transient could be powered by the recombination of 3.4 × 10−5M⊙ of hydrogen in an outflow, or the contraction of an inflated envelope of mass ≈10−6M⊙ that formed during the merger. The observed ejecta mass 320 days after the peak of the optical transient is ≈1.3 × 10−4M⊙, consistent with the idea that a fraction of the ejecta might be unobservable in the light curve. Energetically, this post-merger ejecta mass suggests a planet at least as massive as Jupiter. Our results suggest that ZTF SLRN-2020 was the result of a merger between a star close to the main sequence and a planet with mass at least several times that of Jupiter.
{"title":"Evolution of the ZTF SLRN-2020 Star-Planet Merger","authors":"Ricardo Yarza, Morgan MacLeod, Benjamin Idini, Ruth Murray-Clay and Enrico Ramirez-Ruiz","doi":"10.3847/2041-8213/ae13b1","DOIUrl":"https://doi.org/10.3847/2041-8213/ae13b1","url":null,"abstract":"We model the optical and infrared transient ZTF SLRN-2020, previously associated with a star-planet merger. We consider the scenario in which orbital decay via tidal dissipation led to the merger, and we find that tidal heating within the star was likely unobservable in the archival image of the system taken 12 yr before the merger. The observed dust formation months before the merger is consistent with a planet of mass Mp ≳ 5MJ ejecting material as it skims the stellar surface. This interaction gradually intensifies, leading to significant mass ejection on a dynamical timescale (≈hours) as the planet plunges into the stellar interior. Part of the recombination transient associated with this dynamical mass ejection might be inaccessible to the optical observations because its duration (≈hours) is comparable to the cadence. Correspondingly, the observed duration of the transient (≈100 days) is inconsistent with a single episode of dynamical mass ejection. Instead, the transient could be powered by the recombination of 3.4 × 10−5M⊙ of hydrogen in an outflow, or the contraction of an inflated envelope of mass ≈10−6M⊙ that formed during the merger. The observed ejecta mass 320 days after the peak of the optical transient is ≈1.3 × 10−4M⊙, consistent with the idea that a fraction of the ejecta might be unobservable in the light curve. Energetically, this post-merger ejecta mass suggests a planet at least as massive as Jupiter. Our results suggest that ZTF SLRN-2020 was the result of a merger between a star close to the main sequence and a planet with mass at least several times that of Jupiter.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145717491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-11DOI: 10.3847/2041-8213/ae247e
Zhuo Liu, Muni Zhou and Nuno F. Loureiro
We investigate the inverse cascade of magnetic energy in decaying, collisionless pair plasmas with moderate to high β values via first-principles numerical simulations and analytical theory. We find that pressure-anisotropy-driven instabilities, in particular the firehose instability, suppress reconnection-driven coalescence of magnetic structures (i.e., inverse transfer) by nullifying magnetic tension. The presence of a magnetic guide field of sufficient strength restores the system’s ability to inverse transfer magnetic energy. These results reveal that inverse energy transfer in collisionless plasmas is not guaranteed, but rather depends sensitively on magnetization. In the astrophysical context, this identifies a kinetic mechanism by which Weibel-generated seed fields may fail to merge consistently, potentially limiting their role in cosmic magnetogenesis.
{"title":"Suppression of Inverse Magnetic Energy Transfer in Collisionless Marginally Magnetized Plasmas","authors":"Zhuo Liu, Muni Zhou and Nuno F. Loureiro","doi":"10.3847/2041-8213/ae247e","DOIUrl":"https://doi.org/10.3847/2041-8213/ae247e","url":null,"abstract":"We investigate the inverse cascade of magnetic energy in decaying, collisionless pair plasmas with moderate to high β values via first-principles numerical simulations and analytical theory. We find that pressure-anisotropy-driven instabilities, in particular the firehose instability, suppress reconnection-driven coalescence of magnetic structures (i.e., inverse transfer) by nullifying magnetic tension. The presence of a magnetic guide field of sufficient strength restores the system’s ability to inverse transfer magnetic energy. These results reveal that inverse energy transfer in collisionless plasmas is not guaranteed, but rather depends sensitively on magnetization. In the astrophysical context, this identifies a kinetic mechanism by which Weibel-generated seed fields may fail to merge consistently, potentially limiting their role in cosmic magnetogenesis.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145717494","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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