物理与天体物理最新文献

{"title":"Evaluating metric and contrastive learning in pretrained models for environmental sound classification","authors":"Feilong Chen ,&nbsp;Zhenjun Zhu ,&nbsp;Chengli Sun ,&nbsp;Linqing Xia","doi":"10.1016/j.apacoust.2025.110593","DOIUrl":"10.1016/j.apacoust.2025.110593","url":null,"abstract":"<div><div>Environmental Sound Classification (ESC) has advanced significantly with the advent of deep learning techniques. This study conducts a comprehensive evaluation of contrastive and metric learning approaches in ESC, introducing the ESC51 dataset, an extension of the ESC50 benchmark that incorporates noise samples from quadrotor Unmanned Aerial Vehicles (UAVs). To enhance classification performance and the discriminative power of embedding spaces, we propose a novel metric learning-based approach, SoundMLR, which employs a hybrid loss function emphasizing metric learning principles. Experimental results demonstrate that SoundMLR consistently outperforms contrastive learning methods in terms of classification accuracy and inference latency, particularly when applied to the lightweight MobileNetV2 pretrained model across ESC50, ESC51, and UrbanSound8K (US8K) datasets. Analyses of confusion matrices and t-SNE visualizations further highlight SoundMLR’s ability to generate compact, distinct feature clusters, enabling more robust discrimination between sound classes. Additionally, we introduce two innovative modules, Spectral Pooling Attention (SPA) and the Feature Pooling Layer (FPL), designed to optimize the MobileNetV2 backbone. Notably, the MobileNetV2 + FPL model, equipped with SoundMLR, achieves an impressive 92.16 % classification accuracy on the ESC51 dataset while reducing computational complexity by 24.5 %. Similarly, the MobileNetV2 + SPA model achieves a peak accuracy of 91.75 % on the ESC50 dataset, showcasing the complementary strengths of these modules. These findings offer valuable insights for the future development of efficient, scalable, and robust ESC systems. The source code for this study is publicly available at <span><span>https://github.com/flchenwhu/ESC-SoundMLR</span><svg><path></path></svg></span>.</div></div>","PeriodicalId":55506,"journal":{"name":"Applied Acoustics","volume":"232 ","pages":"Article 110593"},"PeriodicalIF":3.4,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultrasensitive metasurface sensor based on quasi-bound states in the continuum","authors":"Ning Li, He Chen, Yunxia Zhao, Yongtian Wang, Zhaoxian Su, Yin Liu, Lingling Huang","doi":"10.1515/nanoph-2024-0728","DOIUrl":"https://doi.org/10.1515/nanoph-2024-0728","url":null,"abstract":"The quasi-bound state in the continuum (quasi-BIC) of dielectric metasurface provides a crucial platform for sensing, because its almost infinite <jats:italic>Q</jats:italic>-factor can greatly enhance the interactions between light waves and the analytes. In this work, we proposed an ultrasensitive all-dielectric metasurface sensor composed of periodic rectangular amorphous silicon pillars on a quartz substrate. By breaking symmetry of two pillars in unit cell, high <jats:italic>Q</jats:italic> quasi-BIC in the continuous near-infrared band can be excited. The magnetic toroidal dipole (MTD) is demonstrated to play a dominating role in the resonant modes by analyzing near-field distribution and multipole decomposition. The asymmetry degree has a significant impact on sensing performance of the proposed metasurface sensor, whose underlying physical mechanisms is analyzed by perturbation theory. The transmission spectrum and sensing performance of the fabricated metasurface sensor were measured. The experimental results show our designed metasurface sensor not only achieve a high sensitivity of 413/RIU, but also shows a high figure of merit (FOM) of 66 RIU<jats:sup>−1</jats:sup>. This work provides excellent prospects for the excitation of strong MTD resonance quasi-BIC in sensing applications.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"95 4 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neural network-based analysis algorithm on Mueller matrix data of spectroscopic ellipsometry for the structure evaluation of nanogratings with various optical constants","authors":"Juwon Jung, Nagyeong Kim, Kibaek Kim, Jongkyoon Park, Yong Jai Cho, Won Chegal, Young-Joo Kim","doi":"10.1515/nanoph-2024-0565","DOIUrl":"https://doi.org/10.1515/nanoph-2024-0565","url":null,"abstract":"Accurate and fast characterization of nanostructures using spectroscopic ellipsometry (SE) is required in both industrial and research fields. However, conventional methods used in SE data analysis often face challenges in balancing accuracy and speed, especially for the <jats:italic>in situ</jats:italic> monitoring on complex nanostructures. Additionally, optical constants are so crucial for accurately predicting structural parameters since SE data were strongly related to them. This study proposes a three-step algorithm designed for fast and accurate extraction of structural parameters from SE measurements. The method utilizes three neural networks, each trained on simulation data, to obtain optical constants and progressively refine the prediction on structural parameters at each step. When tested on both simulation and measurement data on the fabricated 1D SiO<jats:sub>2</jats:sub> nanograting specimen, the algorithm demonstrated both high accuracy and fast analysis speed, with average mean absolute error (MAE) of 0.103 nm and analysis speed of 132 ms. Also, the proposed algorithm shows more flexibility in accounting for any change of optical constants to serve as a more efficient solution in the real-time monitoring.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"62 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optical readout of a superconducting qubit using a piezo-optomechanical transducer","authors":"T. C. van Thiel, M. J. Weaver, F. Berto, P. Duivestein, M. Lemang, K. L. Schuurman, M. Žemlička, F. Hijazi, A. C. Bernasconi, C. Ferrer, E. Cataldo, E. Lachman, M. Field, Y. Mohan, F. K. de Vries, C. C. Bultink, J. C. van Oven, J. Y. Mutus, R. Stockill, S. Gröblacher","doi":"10.1038/s41567-024-02742-3","DOIUrl":"https://doi.org/10.1038/s41567-024-02742-3","url":null,"abstract":"<p>Superconducting quantum processors have made important progress in size and computing potential. However, the practical cryogenic limitations of operating large numbers of superconducting qubits are becoming a bottleneck for further scaling. Due to the low thermal conductivity and the dense optical multiplexing capacity of telecommunications fibre, converting qubit signal processing to the optical domain using microwave-to-optics transduction would substantially relax the strain on cryogenic space and thermal budgets. Here we demonstrate optical readout of a superconducting transmon qubit through an optical fibre connected via a coaxial cable to a fully integrated piezo-optomechanical transducer. Using a demolition readout technique, we achieve a single-shot readout fidelity of 81%. Our results illustrate the benefits of piezo-optomechanical transduction for low-dissipation operation of large quantum processors.</p>","PeriodicalId":19100,"journal":{"name":"Nature Physics","volume":"79 5 Pt 1 1","pages":""},"PeriodicalIF":19.6,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperature and density profiles in the corona of main-sequence stars induced by stochastic heating in the chromosphere","authors":"Luca Barbieri, Lapo Casetti, Andrea Verdini, Simone Landi","doi":"10.1051/0004-6361/202452879","DOIUrl":"https://doi.org/10.1051/0004-6361/202452879","url":null,"abstract":"All but the most massive main-sequence stars are expected to have a rarefied and hot (million-Kelvin) corona like the Sun. How such a hot corona is formed and supported has not been completely understood yet, even in the case of the Sun. Recently, a new model of a confined plasma atmosphere has been introduced and applied to the solar case, showing that rapid, intense, intermittent and short-lived heating events in the high chromosphere can drive the coronal plasma into a stationary state with temperature and density profiles similar to those observed in the solar atmosphere. In this paper we apply the model to main-sequence stars, showing that it predicts the presence of a solar-like hot and rarefied corona for all such stars, regardless of their mass. However, the model is not applicable as such to the most massive main-sequence stars, because the latter lack the convective layer generating the magnetic field loop structures supporting a stationary corona, whose existence is assumed by the model. We also discuss the role of stellar mass in determining the shape of the temperature and density profiles.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"JOYS: The [D/H] abundance derived from protostellar outflows across the Galactic disk measured with JWST","authors":"L. Francis, E. F. van Dishoeck, A. Caratti o Garatti, M. L. van Gelder, C. Gieser, H. Beuther, T. P. Ray, L. Tychoniec, P. Nazari, S. Reyes, P. J. Kavanagh, P. Klaassen, M. Güdel, T. Henning","doi":"10.1051/0004-6361/202451629","DOIUrl":"https://doi.org/10.1051/0004-6361/202451629","url":null,"abstract":"&lt;i&gt;Context&lt;i/&gt;. The total deuterium abundance [D/H] in the universe is set by just two processes: the creation of deuterium in Big Bang nucleosynthesis at an abundance of [D/H] = 2.58 ± 0.13 × 10&lt;sup&gt;−5&lt;sup/&gt;, and its destruction within stellar interiors (astration). Measurements of variations in the total [D/H] abundance can thus potentially provide a probe of Galactic chemical evolution. However, most observational measurements of [D/H] are only sensitive to the gas-phase deuterium, and the amount of deuterium sequestered in dust grains is debated. With the launch of the James Webb Space Telescope (JWST), it is now possible to measure the gas-phase [D/H] at unprecedented sensitivity and distances through observation of mid-IR lines of H&lt;sub&gt;2&lt;sub/&gt; and HD. Comparisons of gas-phase [D/H] with the constraints on the total [D/H] from the primordial abundance and Galactic chemical evolution models can provide insight into the degree of Deuterium lock-up in grains and the star formation history of our Galaxy.&lt;i&gt;Aims&lt;i/&gt;. We use data from the JWST Observations of Young protoStars (JOYS) program of 5 nearby and resolved low-mass protostellar outflows and 5 distant high-mass protostellar outflows taken with the JWST Mid Infrafred Instrument (MIRI) Medium Resolution Spectrometer (MRS) to measure gas-phase [D/H] via H&lt;sub&gt;2&lt;sub/&gt; and HD lines, assuming the gas is fully molecular.&lt;i&gt;Methods&lt;i/&gt;. We extract spectra from various locations in the outflows. Using a rotational diagram analysis covering lines of H&lt;sub&gt;2&lt;sub/&gt; and HD with similar excitation energies, we derive the column density of HD and H&lt;sub&gt;2&lt;sub/&gt; or their upper limits. We then calculate the gas-phase [D/H] from the column density results, and additionally apply a correction factor for the effect of chemical conversion of HD to atomic D and non-LTE excitation on the HD abundance in the shocks. To investigate the spatial distribution of the bulk gas and species refractory species associated with the dust grains, we also construct integrated line intensity maps of H&lt;sub&gt;2&lt;sub/&gt;, HD, [Fe II], [Fe I], and [S I] lines.&lt;i&gt;Results&lt;i/&gt;. A comparison of gas-phase [D/H] between our low-mass sources shows variations of up to a factor of ~4, despite these sources likely having formed in nearly the same region of the Galactic disk that would be expected to have nearly constant total [D/H]. Most measurements of gas-phase [D/H] from our work or previous studies produce [D/H] ≲ 1.0 × 10&lt;sup&gt;−5&lt;sup/&gt;, a factor of 2-4 lower than found from local UV absorption lines and as expected from Galactic chemical evolution models. In the integrated line intensity maps, the morphology of the HD R(6) line emission is strongly correlated with the H&lt;sub&gt;2&lt;sub/&gt; S(7), [S I], and [Fe I] lines which mostly trace high velocity jet knots and bright bow-shocks. In our extracted spectra along the outflows, there is similarly a strong correlation between the H&lt;sub&gt;2&lt;sub/&gt; and HD column density and the [S I] and [Fe I] line flux, ","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"29 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Primordial black holes from first-order phase transition in the singlet-extended SM","authors":"Dorival Gonçalves, Ajay Kaladharan, Yongcheng Wu","doi":"10.1103/physrevd.111.035009","DOIUrl":"https://doi.org/10.1103/physrevd.111.035009","url":null,"abstract":"Supercooled first-order phase transition (FOPT) can lead to the formation of primordial black holes (PBHs). This scenario imposes stringent requirements on the profile of the effective potential. In this work, we use the singlet extended Standard Model (xSM) as a benchmark model to investigate this possibility at the electroweak scale. The PBHs formed during a supercooled FOPT have a narrow mass distribution around the mass of Earth. This distribution is closely tied to the temperature at which the PBHs form, corresponding to the FOPT at the electroweak scale. This scenario can be probed with microlensing experiments, space-based gravitational wave detectors, and collider experiments. Remarkably, the future space-based gravitational wave detector LISA will hold the potential to either confirm this scenario that leads to PBH formation across the observable Universe in the xSM or completely rule it out. Interestingly, our findings suggest that PBHs within the xSM framework may align with observations of the six ultrashort timescale events reported by the OGLE microlensing experiment. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20167,"journal":{"name":"Physical Review D","volume":"167 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stellar magnetic activity in Earth 2.0 candidates based on LAMOST DR10","authors":"Tianhao Su, Liyun Zhang, Xianming L. Han, Prabhakar Misra, Zhongzhong Zhu, Qingfeng Pi","doi":"10.1051/0004-6361/202452042","DOIUrl":"https://doi.org/10.1051/0004-6361/202452042","url":null,"abstract":"<i>Aims<i/>. Stellar chromospheric activity can impact the search for exoplanets. Earth 2.0 (ET 2.0) is a space telescope designed for exoplanet detection. In this work, we survey the stellar chromospheric activity in the ET 2.0 target regions to enhance the detection rate of exoplanets.<i>Methods<i/>. This work uses H<i>α<i/> and Ca II H&K lines as indicators of chromospheric activity and conducts a survey of stellar chromospheric activity in the ET 2.0 target regions using LAMOST low- and medium-resolution spectra. After cross-referencing with the ET 2.0 input catalog, we obtained over 349 000 low-resolution spectra and over 30 000 medium-resolution spectra from LAMOST. We quantified the chromospheric activity intensity for all spectra and selected the results for those with a signal-to-noise ratio (S/N) above 10 for further studies of the chromospheric activity. The quantification standards include equivalent width (EW) and the ratio of bolometric luminosity to the corresponding spectral line luminosity (<i>L<i/><sub><i>Hα<i/><sub/>/<i>L<i/><sub><i>bol<i/><sub/>, <i>L<i/><sub><i>CaH<i/><sub/>/<i>L<i/><sub><i>bol<i/><sub/>, <i>L<i/><sub><i>CaK<i/><sub/>/<i>L<i/><sub><i>bol<i/><sub/>, <i>L<i/><sub><i>HK<i/><sub/>/<i>L<i/><sub><i>bol<i/><sub/>).<i>Results<i/>. Utilizing H<i>α<i/> and Ca II H&K lines, we evaluated the chromospheric activity for over 320 000 and 110 000 spectra based on LAMOST low-resolution spectra, respectively. In addition, we evaluated chromospheric activity for 34000 spectra using H<i>α<i/> lines based on medium-resolution spectra. We selected samples that are suitable for exoplanet studies, based on H<i>α<i/> and Ca II H&K lines. Additionally, we explored the relationship between stellar activity observed by LAMOST and rotation periods obtained from Kepler and TESS surveys. Our findings confirm the presence of two distinct regions in terms of their relationship between stellar activity and Rossby number (Ro), namely: saturated and unsaturated. We determined a critical Ro in the range of 0.09–0.12 using the r-band spectra of 11 921 stars and u-band spectra of 6120 stars. Moreover, we observe that Ca II H&K lines exhibit greater sensitivity to Ro in the unsaturated region, compared to Ha line measurements. Lastly, we have established positive correlations between various activity indicators, including <i>R<i/>′<sub><i>CaK<i/><sub/>, <i>R<i/>′<sub><i>CaH<i/><sub/>, <i>R<i/>′<sub><i>HK<i/><sub/>, and <i>R<i/>′<sub><i>Hα<i/><sub/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"14 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The ALMA-ATOMS survey: Vibrationally excited HC3N lines in hot cores","authors":"Li Chen, Sheng-Li Qin, Tie Liu, Paul F. Goldsmith, Xunchuan Liu, Yaping Peng, Xindi Tang, Guido Garay, Zhiping Kou, Mengyao Tang, Patricio Sanhueza, Zi-Yang Li, Prasanta Gorai, Swagat R. Das, Leonardo Bronfman, Lokesh Dewangan, Pablo García, Shanghuo Li, Chang Won Lee, Hong-Li Liu, L. Viktor Tóth, James O. Chibueze, Jihye Hwang, Xiaohu Li, Fengwei Xu, Jiahang Zou, Wenyu Jiao, Zhenying Zhang, Yong Zhang","doi":"10.1051/0004-6361/202452598","DOIUrl":"https://doi.org/10.1051/0004-6361/202452598","url":null,"abstract":"<i>Context.<i/> Interstellar molecules are excellent tools for studying the physical and chemical environments of massive star-forming regions. In particular, the vibrationally excited HC<sub>3<sub/>N (HC<sub>3<sub/>N*) lines are the key tracers for probing hot cores environments.<i>Aims.<i/> We present the Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm observations of HC<sub>3<sub/>N* lines in 60 hot cores and investigate how the physical conditions affect the excitation of HC<sub>3<sub/>N* transitions.<i>Methods.<i/> We used the XCLASS for line identification. Under the assumption of local thermodynamic equilibrium, we derived the rotation temperature and column density of HC<sub>3<sub/>N* transitions in hot cores. Additionally, we calculated the H<sub>2<sub/> column density and number density, along with the abundance of HC<sub>3<sub/>N* relative to H<sub>2<sub/>, to enable a comparison of the physical properties of hot cores with different numbers of HC<sub>3<sub/>N* states.<i>Results.<i/> We have detected HC<sub>3<sub/>N* lines in 52 hot cores, 29 of which show more than one vibrationally excited state. Hot cores with higher gas temperatures have more detections of these vibrationally excited lines. The excitation of HC<sub>3<sub/>N* requires dense environments, and its spatial distribution is affected by the presence of UC HII regions. The observed column density of HC<sub>3<sub/>N* contributes to the number of HC<sub>3<sub/>N* states in hot-core environments.<i>Conclusions.<i/> After analyzing the various factors influencing HC<sub>3<sub/>N* excitation in hot cores, we conclude that the excitation of HC<sub>3<sub/>N* is mainly driven by mid-IR pumping, while collisional excitation is ineffective.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A multi-wavelength view of the isolated neutron star eRASSU J065715.3+260428⋆","authors":"J. Kurpas, A. M. Pires, A. D. Schwope, Z. C. Pan, Z. L. Zhang, L. Qian, F. Haberl, L. Ji, I. Traulsen","doi":"10.1051/0004-6361/202452353","DOIUrl":"https://doi.org/10.1051/0004-6361/202452353","url":null,"abstract":"On the premise of a soft spectral distribution and absence of counterparts, the X-ray source eRASSU J065715.3+260428 was recently identified as a likely thermally emitting isolated neutron star (XINS) in a search in the <i>SRG<i/>/eROSITA All-Sky Survey. We investigated the nature and evolutionary state of the neutron star through a dedicated multi-wavelength follow-up observational campaign with <i>XMM-Newton<i/>, <i>NICER<i/>, <i>FAST<i/>, and <i>ESO-VLT<i/>, complemented by the analysis of archival <i>Fermi<i/>-<i>LAT<i/> observations. The coherent timing analysis of the X-ray observations unveiled the rotation period of the XINS, <i>P<i/> = 261.085400(4) ms, and its spin-down rate, s s<sup>−1<sup/> (errors are 1<i>σ<i/> confidence levels). The nearly sinusoidal pulse profile has a pulsed fraction of ∼15% (0.2 − 2 keV). No optical counterparts are detected down to 27.3 mag (5<i>σ<i/>, <i>R<i/> band) in the <i>ESO-VLT<i/> FORS2 imaging, implying a large X-ray-to-optical flux ratio above 5200. The X-ray spectrum of the source is best described by a composite phenomenological model consisting of two thermal components, either a double blackbody continuum with temperatures 90 eV and 220 eV or a hydrogen neutron star atmosphere of temperature log(<i>T<i/>/K)∼5.8 combined with a hot blackbody of 250 eV, in both cases modified by an absorption feature at low energies, ∼0.3 keV with an equivalent width of ∼100 eV. The presence of faint non-thermal hard X-ray tails is ruled out above (2.1 ± 1.8)% of the source unabsorbed flux. Radio searches at 1 − 1.5 GHz with <i>FAST<i/> yielded negative results, with a deep upper limit on the pulsed flux of 1.4 μJy (10<i>σ<i/>). Similarly, no significant spatial or pulsed signals were detected in sixteen years of <i>Fermi<i/>-<i>LAT<i/> observations. The most likely interpretation is that the source is a middle-aged spin-powered pulsar, which can also be identified as PSR J0657+2604. The absence of non-thermal X-ray, radio, or gamma-ray emission within current limits suggests either an unfavourable viewing geometry or unusual magnetospheric properties. Additional observations are needed to check for faint hard X-ray tails, investigate the presence of diffuse emission from a pulsar-wind nebula, and obtain a more accurately sampled timing solution.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"78 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}