分类： 计算机科学 >> 计算机软件 提交时间： 2024-09-25
摘要： This paper presents a distributed software framework for drone swarm applications, focusing on the OWL-Swarm framework. The framework addresses challenges in task allocation and coordination inherent in swarm robotics. It introduces a modular architecture based on the Robot Operating System (ROS), enabling seamless integration of various algorithms and functionalities. The Captain service acts as the central orchestrator, managing mission execution, task allocation, and data sharing among drones. The framework supports both single#2;drone and collaborative tasks, with mechanisms for distributed scheduling and dynamic task re-allocation. The effectiveness of the framework is demonstrated through use cases involving cooperative obstacle avoidance, coordinated search and target tracking. The modular and extensible design of the framework allows for easy customization and adaptation to various drone swarm applications, making it a valuable tool for research and development in this field.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Losses are ubiquitous and unavoidable in nature inhibiting the performance of most optical processes. Manipulating losses to adjust the dissipation of photons is analogous to braking a running car that is as important as populating photons via a gain medium. Here, we introduce the transient loss boundary into a photon populated cavity that functions as a photon brake and probe photon dynamics by engineering the brake timing and brake strength. Coupled cavity photons can be distinguished by stripping one photonic mode through controlling the loss boundary, which enables the transition from a coupled to an uncoupled state. We interpret the transient boundary as a perturbation by considering both real and imaginary parts of permittivity, and the dynamic process is modelled with a temporal two-dipole oscillator, one with the natural resonant polarization and the other with a frequency-shift polarization. The model unravels the underlying mechanism of concomitant coherent spectral oscillations and generation of tone-tuning cavity photons in the braking process. By synthesizing the temporal loss boundary into a photon populated cavity, a plethora of interesting phenomena and applications are envisioned such as the observation of quantum squeezed states, low-loss nonreciprocal waveguides and ultrafast beam scanning devices.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： The combinations of artificial intelligence and lasers provide powerful ways to form smart light sources with ground-breaking functions. Here, a Raman fiber laser (RFL) with reconfigurable and programmable spectra in an ultra-wide bandwidth is developed based on spectral-spatial manipulation of light in multimode fiber (MMF). The proposed fiber laser uses nonlinear gain from cascaded stimulated Raman scattering, random distributed feedback from Rayleigh scattering, and point feedback from an MMF-based smart spectral filter. Through wavefront shaping controlled by a genetic algorithm, light of selective wavelength(s) can be focused in the MMF, forming the filter that, together with the active part of the laser, actively shape the output spectrum with a high degree of freedom. We achieved arbitrary spectral shaping of the cascaded RFL (e.g., continuously tunable single-wavelength and multi-wavelength laser with customizable linewidth, mode separation, and power distribution) from the 1st- to the 3rd-order Stokes emission by adjusting the pump power and auto-optimization of the smart filter. Our research uses artificial-intelligence controlled light manipulation in a fiber platform with multi-eigenmodes and nonlinear gain, mapping the spatial control into the spectral domain as well as extending the linear control of light in MMF to active light emission, which is of great significance for applications in optical communication, sensing, and spectroscopy.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Ultrasensitive terahertz sensing of highly absorptive aqueous solutions remains challenging due to strong absorption of water in the terahertz regime. Here, we experimentally demonstrate a cost-effective metamaterial-based sensor integrated with terahertz time-domain spectroscopy for highly absorptive water-methanol mixture sensing. This metamaterial has simple asymmetric wire structures that support multiple resonances including a fundamental Fano resonance and higher order dipolar resonance in the terahertz regime. Both the resonance modes have strong intensity in the transmission spectra which we exploit for detection of the highly absorptive water-methanol mixtures. The experimentally characterized sensitivities of the Fano and dipole resonances for the water-methanol mixtures are found to be 160 and 305 GHz/RIU, respectively. This method provides a route for readily available metamaterial-assisted terahertz spectroscopy for ultrasensitive sensing of highly absorptive chemical and biochemical materials with multiple resonances and high accuracy.
分类： 地球科学 >> 地理学 提交时间： 2021-07-23 合作期刊: 《干旱区科学》
摘要： The accurate simulation and prediction of runoff in alpine glaciated watersheds is of increasing importance for the comprehensive management and utilization of water resources. In this study, long short-term memory (LSTM), a state-of-the-art artificial neural network algorithm, is applied to simulate the daily discharge of two data-sparse glaciated watersheds in the Tianshan Mountains in Central Asia. Two other classic machine learning methods, namely extreme gradient boosting (XGBoost) and support vector regression (SVR), along with a distributed hydrological model (Soil and Water Assessment Tool (SWAT) and an extended SWAT model (SWAT_Glacier) are also employed for comparison. This paper aims to provide an efficient and reliable method for simulating discharge in glaciated alpine regions that have insufficient observed meteorological data. The two typical basins in this study are the main tributaries (the Kumaric and Toxkan rivers) of the Aksu River in the south Tianshan Mountains, which are dominated by snow and glacier meltwater and precipitation. Our comparative analysis indicates that simulations from the LSTM shows the best agreement with the observations. The performance metrics Nash-Sutcliffe efficiency coefficient (NS) and correlation coefficient (R2) of LSTM are higher than 0.90 in both the training and testing periods in the Kumaric River Basin, and NS and R2 are also higher than 0.70 in the Toxkan River Basin. Compared to classic machine learning algorithms, LSTM shows significant advantages over most evaluating indices. XGBoost also has high NS value in the training period, but is prone to overfitting the discharge. Compared with the widely used hydrological models, LSTM has advantages in predicting accuracy, despite having fewer data inputs. Moreover, LSTM only requires meteorological data rather than physical characteristics of underlying data. As an extension of SWAT, the SWAT_Glacier model shows good adaptability in discharge simulation, outperforming the original SWAT model, but at the cost of increasing the complexity of the model. Compared with the oftentimes complex semi-distributed physical hydrological models, the LSTM method not only eliminates the tedious calibration process of hydrological parameters, but also significantly reduces the calculation time and costs. Overall, LSTM shows immense promise in dealing with scarce meteorological data in glaciated catchments.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Superluminal tunneling of light through a barrier has attracted broad interest in the last several decades. Despite the observation of such phenomena in various systems, it has been under intensive debate whether the transmitted light truly carry the information of the original pulse. Here we report observation of anomalous time response for terahertz electromagnetic pulses passing through thin metal films, with the pulse shape of the transmitted beam faithfully resembling that of the incident beam. A causal theoretical analysis is developed to explain the experiments, though the theory of Special Relativity may confront a challenge in this exceptional circumstance. These findings may facilitate future applications in high-speed optical communication or signal transmission, and may reshape our fundamental understanding about the tunneling of light.
分类： 物理学 >> 核物理学 提交时间： 2025-05-29
Han, Mr. Xu
Ye, Dr. Tao
Chen, Prof. Zhenpeng
Guo, Dr. Hairui
Sun, Prof. Weili
Sun, Mr. Zhihao
Fan, Miss Haoyang
摘要： Based on the Generalized reduced R-matrix theory, the RAC program (R-matrix analysis code) is used to analyze the experimental data of all the nuclear reaction channels related to the 5He system. The current calculations provide accurate and reliable evaluation data, and are in good agreement with the experimental data. In this work, self-consistent for each reaction evaluation data are obtained by multi-channel and multi-energy fitting, in particular, the error propagation theory of Generalized Least Squares is used to give the error of the evaluation data and the covariance matrix of the integral cross section. This R-matrix analysis for the 5He system has the following three features. First, for the first time, the error in the evaluation data of the T(d,n)4He reaction cross section and the covariance matrix of the integral cross section are given. Second, we use only one set of R-matrix parameters to depict the reaction cross section of each reaction channel of the 5He system for the whole energy region in our work. Third, in this evaluation, we have taken into account some of the latest measured experimental data, especially after 2000. The T(d,n)4He reaction cross section at 0.1 MeV and below has been carefully studied. The effect of different energy levels in T(d,n)4He has been analyzed, with the energy levels 3/2+ making a major contribution to cross section, and the role of S-wave and D-wave from 3/2- determines the lean forward trend of the angular distributions at 0.01 MeV - 0.1 MeV.
分类： 物理学 >> 核物理学 提交时间： 2025-04-03
Han, Mr. Xu
Ye, Dr. Tao
Chen, Prof. Zhenpeng
Guo, Dr. Hairui
Sun, Prof. Weili
Sun, Mr. Zhihao
Fan, Miss Haoyang
摘要： Based on the Generalized reduced R-matrix theory, the RAC program (R-matrix analysis code) is used to analyze the experimental data of all the nuclear reaction channels related to the 5He system. The current calculations provide accurate and reliable evaluation data, and are in good agreement with the experimental data. In this work, self-consistent for each reaction evaluation data are obtained by multi-channel and multi-energy fitting, in particular, the error propagation theory of Generalized Least Squares is used to give the error of the evaluation data and the covariance matrix of the integral cross section. This R-matrix analysis for the 5He system has the following three features. First, for the first time, the error in the evaluation data of the T(d,n)4He reaction cross section and the covariance matrix of the integral cross section are given. Second, we use only one set of R-matrix parameters to depict the reaction cross section of each reaction channel of the 5He system for the whole energy region in our work. Third, in this evaluation, we have taken into account some of the latest measured experimental data, especially after 2000. The T(d,n)4He reaction cross section at 0.1 MeV and below has been carefully studied. The effect of different energy levels in T(d,n)4He has been analyzed, with the energy levels 3/2+ making a major contribution to cross section, and the role of S-wave and D-wave from 3/2- determines the lean forward trend of the angular distributions at 0.01 MeV - 0.1 MeV.
分类： 核科学技术 >> 核科学与技术 提交时间： 2025-03-07
Sun, Zhihao
Fan, Haoyang
E, Yiting
Guo, Hairui
Ye, Tao
Sun, Weili
Han, Xu
Chen, Wendi
Ying, Yangjun
Xu, Yongli
Zhang, Donghong
Han, Yinlu
摘要： This study investigates the mechanism of 6Li+7Li anomalous large-angle scattering. First, elastic scatteringis analyzed using an optical model with the S˜ao Paulo potential, and inelastic scattering to the first excitedstate of 7Li is analyzed by distorted wave born approximation method. The experimental data of the elasticscattering angular distributions could be described reasonably well by the optical model at forward angles; however,anomalous large-angle scattering is observed in the angular distributions of both the elastic and inelasticchannels for all measured energies. Elastic and inelastic scatterings are investigated using the coupled reactionchannel method. The elastic and inelastic scattering, transfer reactions for the ground and excited states, andtheir coupling effects are considered in the coupled reaction channel scheme. In addition, the influence of thebreakup effects of the weakly bound 6Li and 7Li is investigated by including three resonance states of 6Li andtwo resonance states of 7Li in the coupled reaction channel framework. The observed anomalous large-anglescattering is explained using the transfer reaction mechanism and breakup effect, and the calculated resultsreproduce the experimental data reasonably well.
分类： 物理学 >> 核物理学 提交时间： 2025-01-20
Chen, Dr. Jia-Hao
Yang, Dr. Bo
Jia, Dr. Qinggang
Li, Mr. Rui
Chen, Dr. Wendi
Guo, Dr. Hairui
Sun, Prof. Weili
Ye, Dr. Tao
摘要： Prompt fission neutron spectra (PFNS) play a significant role in nuclear science and technology. In this work, we report on the evaluation of the PFNS for ^{239}\text{Pu} through both differential and integral experimental data. We introduce a method that leverages integral criticality benchmark experiments to constrain the PFNS data. By constructing a covariance matrix, we perturbed the measured central values of the PFNS. The PFNS were sampled using two types of covariance matrices. One was generated with an assumed correlation matrix and incorporating experimental uncertainties, and the other was derived directly from experiment reports. The Joint Monte Carlo Transport (JMCT) code was employed to perform transport simulations on five criticality benchmark assemblies, utilizing the perturbed PFNS data. The extensive simulations resulted in an optimized PFNS that showed improved agreement with integral criticality benchmark experiments. This study introduces a novel approach for optimizing differential experimental data through integral experiments, especially when a covariance matrix is not provided.
分类： 生物学 >> 生物物理学 >> 肿瘤学 提交时间： 2016-05-11
Hu, Shi
Guo, Huaizu
Qian, Weizhu
Hou, Sheng
Li, Bohua
Guo, Yajun
Hu, Shi
Guo, Huaizu
Qian, Weizhu
Hou, Sheng
Li, Bohua
Guo, Yajun
Hu, Shi
Sun, Yuna
Rao, Zihe
Hu, Shi
Sun, Yuna
Rao, Zihe
Lou, Zhiyong
Hu, Shi
摘要： Human epidermal growth factor receptors (HERs or ErbBs) play crucial roles in numerous cellular processes. ErbB2 is a key member of ErbB family, and its overexpression is recognized as a frequent molecular abnormality. In cancer, this overexpression correlates with aggressive disease and poor patient outcomes. Dimer-dependent phosphorylation is a key event for the signal transduction of ErbBs. However, the molecular mechanism of the dimerization of ErbB2 remains elusive. In the present work, we report the homodimer architecture of the ErbB2 extracellular domain (ECD) which is unique compared with other dimer-models of ErbBs. The structure of the ErbB2 ECD homodimer represents a "back to head" interaction, in which a protruding beta-hairpin arm in domain II of one ErbB2 protomer is inserted into a C-shaped pocket created by domains I-III of the adjacent ErbB2 protomer. This dimerized architecture and its impact on the phosphorylation of ErbB2 intracellular domain were further verified by a mutagenesis study. We also elucidated the different impacts of two clinically administered therapeutic antibodies, trastuzumab and pertuzumab, on ErbB2 dimerization. This information not only provides an understanding of the molecular mechanism of ErbBs dimerization but also elucidates ErbB2-targeted therapy at the molecular level.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Xiaofeng Wang
Weili Lin
Jujia Zhang
Tianmeng Zhang
Yongzhi Cai
Kaicheng Zhang
Alexei V. Filippenko
Melissa Graham
Keiichi Maeda
Jun Mo
Danfeng Xiang
Gaobo Xi
Shengyu Yan
Lifan Wang
Lingjun Wang
Koji Kawabata
Qian Zhai
摘要： ASASSN-14ms may represent the most luminous Type Ibn supernova (SN~Ibn) ever detected, with an absolute U-band magnitude brighter than -22.0 mag and a total bolometric luminosity >1.0x10^{44} erg/s near maximum light. The early-time spectra of this SN are characterized by a blue continuum on which are superimposed narrow P~Cygni profile lines of He I, suggesting the presence of slowly moving (~1000 km/s), He-rich circumstellar material (CSM). At 1--2 months after maximum brightness, the He I line profiles become only slightly broader, with blueshifted velocities of 2000--3000 km/s, consistent with the CSM shell being continuously accelerated by the SN light and ejecta. Like most SNe~Ibn, the light curves of ASASSN-14ms show rapid post-peak evolution, dropping by ~7 mag in the V band over three months. Such a rapid post-peak decline and high luminosity can be explained with interaction between SN ejecta and helium-rich CSM of 0.9~M_{\odot} at a distance of~10^{15} cm. The CSM around ASASSN-14ms is estimated to originate from a pre-explosion event with a mass-loss rate of 6.7~M_\odot /yr (assuming a velocity of ~1000 km/s), which is consistent with abundant He-rich material violently ejected during the late Wolf-Rayet (WN9-11 or Opfe) stage. After examining the light curves for a sample of SNe~Ibn, we find that the more luminous ones tend to have slower post-peak decline rates, reflecting that the observed differences may arise primarily from discrepancies in the CSM distribution around the massive progenitors.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jie Lin
Xiaofeng Wang
Jun Mo
Gaobo Xi
Jicheng Zhang
Xiaojun Jiang
Jianrong Shi
Xiaobin Zhang
Xiaoming Zhang
Zixuan Wei
Limeng Ye
Chengyuan Wu
Shengyu Yan
Zhihao Chen
Wenxiong Li
Xue Li
Weili Lin
Han Lin
Hanna Sai
Danfeng Xiang
摘要： Tsinghua University-Ma Huateng Telescopes for Survey (TMTS), located at Xinglong Station of NAOC, has a field of view upto 18 deg^2. The TMTS has started to monitor the LAMOST sky areas since 2020, with the uninterrupted observations lasting for about 6 hours on average for each sky area and a cadence of about 1 minute. Here we introduce the data analysis and preliminary scientific results for the first-year observations, which covered 188 LAMOST plates ( about 1970 deg^2). These observations have generated over 4.9 million uninterrupted light curves, with at least 100 epochs for each of them. These light curves correspond to 4.26 million Gaia-DR2 sources, among which 285 thousand sources are found to have multi-epoch spectra from the LAMOST. By analysing these light curves with the Lomb-Scargle periodograms, we identify more than 3700 periodic variable star candidates with periods below 7.5 hours, primarily consisting of eclipsing binaries and Delta Scuti stars. Those short-period binaries will provide important constraints on theories of binary evolution and possible sources for space gravitational wave experiments in the future. Moreover, we also identified 42 flare stars by searching rapidly-evolving signals in the light curves. The densely-sampled light curves from the TMTS allow us to better quantify the shapes and durations for these flares.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Qichun Liu
Jie Lin
Xiaofeng Wang
Shenghong Gu
Jianrong Shi
Liyun Zhang
Gaobo Xi
Jun Mo
Yongzhi Cai
Liyang Chen
Zhihao Chen
Fangzhou Guo
Xiaojun Jiang
Gaici Li
Wenxiong Li
Han Lin
Weili Lin
Jialian Liu
Cheng Miao
Xiaoran Ma
摘要： Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) aims to detect fast-evolving transients in the Universe, which has led to the discovery of thousands of short-period variables and eclipsing binaries since 2020. In this paper, we present the observed properties of 125 flare stars identified by the TMTS within the first two years, with an attempt to constrain their eruption physics. As expected, most of these flares were recorded in late-type red stars with G_{\rm BP}-G_{\rm RP} > 2.0 mag, however, the flares associated with bluer stars tend to be on average more energetic and have broader profiles. The peak flux (F_peak) of the flare is found to depend strongly on the equivalent duration (ED) of the energy release, i.e., F_{{\rm peak}} \propto {\rm ED}^{0.72\pm0.04}, which is consistent with results derived from the Kepler and Evryscope samples. This relation is likely related to the magnetic loop emission, while -- for the more popular non-thermal electron heating model -- a specific time evolution may be required to generate this relation. We notice that flares produced by hotter stars have a flatter F_{{\rm peak}} \propto {\rm ED} relation compared to that from cooler stars. This is related to the statistical discrepancy in light-curve shape of flare events with different colors. In spectra from LAMOST, we find that flare stars have apparently stronger H alpha emission than inactive stars, especially at the low temperature end, suggesting that chromospheric activity plays an important role in producing flares. On the other hand, the subclass having frequent flares are found to show H alpha emission of similar strength in their spectra to that recorded with only a single flare but similar effective temperature, implying that the chromospheric activity may not be the only trigger for eruptions.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Qichun Liu
Jie Lin
Xiaofeng Wang
Shenghong Gu
Jianrong Shi
Liyun Zhang
Gaobo Xi
Jun Mo
Yongzhi Cai
Liyang Chen
Zhihao Chen
Fangzhou Guo
Xiaojun Jiang
Gaici Li
Wenxiong Li
Han Lin
Weili Lin
Jialian Liu
Cheng Miao
Xiaoran Ma
摘要： Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) aims to detect fast-evolving transients in the Universe, which has led to the discovery of thousands of short-period variables and eclipsing binaries since 2020. In this paper, we present the observed properties of 125 flare stars identified by the TMTS within the first two years, with an attempt to constrain their eruption physics. As expected, most of these flares were recorded in late-type red stars with G_{\rm BP}-G_{\rm RP} > 2.0 mag, however, the flares associated with bluer stars tend to be on average more energetic and have broader profiles. The peak flux (F_peak) of the flare is found to depend strongly on the equivalent duration (ED) of the energy release, i.e., F_{{\rm peak}} \propto {\rm ED}^{0.72\pm0.04}, which is consistent with results derived from the Kepler and Evryscope samples. This relation is likely related to the magnetic loop emission, while -- for the more popular non-thermal electron heating model -- a specific time evolution may be required to generate this relation. We notice that flares produced by hotter stars have a flatter F_{{\rm peak}} \propto {\rm ED} relation compared to that from cooler stars. This is related to the statistical discrepancy in light-curve shape of flare events with different colors. In spectra from LAMOST, we find that flare stars have apparently stronger H alpha emission than inactive stars, especially at the low temperature end, suggesting that chromospheric activity plays an important role in producing flares. On the other hand, the subclass having frequent flares are found to show H alpha emission of similar strength in their spectra to that recorded with only a single flare but similar effective temperature, implying that the chromospheric activity may not be the only trigger for eruptions.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jie Lin
Chengyuan Wu
Xiaofeng Wang
Péter Németh
Herang Xiong
Tao Wu
Alexei Filippenko
Yongzhi Cai
Thomas Brink
Shengyu Yan
Xiangyun Zeng
Yangpin Luo
Danfeng Xiang
Jujia Zhang
Weikang Zheng
Yi Yang
Jun Mo
Gaobo Xi
Jicheng Zhang
Abdusamatjan Iskandar
摘要： Blue large-amplitude pulsators (BLAPs) represent a new and rare class of hot pulsating stars with unusually large amplitudes and short periods. Up to now, only 24 confirmed BLAPs have been identified from more than one billion monitored stars, including a group with pulsation period longer than \sim 20 min (classical BLAPs, hereafter) and the other group with pulsation period below \sim 8 min. The evolutionary path that could give rise to such kinds of stellar configurations is unclear. Here we report on a comprehensive study of the peculiar BLAP discovered by the Tsinghua University - Ma Huateng Telescopes for Survey (TMTS), TMTS J035143.63+584504.2 (TMTS-BLAP-1). This new BLAP has an 18.9 min pulsation period and is similar to the BLAPs with a low surface gravity and an extended helium-enriched envelope, suggesting that it is a low-gravity BLAP at the shortest-period end. In particular, the long-term monitoring data reveal that this pulsating star has an unusually large rate of period change, P_dot/P=2.2e-6/yr. Such a significant and positive value challenges its origins from both helium-core pre-white-dwarfs and core helium-burning subdwarfs, but is consistent with that derived from shell helium-burning subdwarfs. The particular pulsation period and unusual rate of period change indicate that TMTS-BLAP-1 is at a short-lived (~10^6 yr) phase of shell-helium ignition before the stable shell-helium burning; in other words, TMTS-BLAP-1 is going through a "Hertzsprung gap" of hot subdwarfs.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jie Lin
Chengyuan Wu
Xiaofeng Wang
Péter Németh
Herang Xiong
Tao Wu
Alexei Filippenko
Yongzhi Cai
Thomas Brink
Shengyu Yan
Xiangyun Zeng
Yangpin Luo
Danfeng Xiang
Jujia Zhang
Weikang Zheng
Yi Yang
Jun Mo
Gaobo Xi
Jicheng Zhang
Abdusamatjan Iskandar
摘要： Blue large-amplitude pulsators (BLAPs) represent a new and rare class of hot pulsating stars with unusually large amplitudes and short periods. Up to now, only 24 confirmed BLAPs have been identified from more than one billion monitored stars, including a group with pulsation period longer than \sim 20 min (classical BLAPs, hereafter) and the other group with pulsation period below \sim 8 min. The evolutionary path that could give rise to such kinds of stellar configurations is unclear. Here we report on a comprehensive study of the peculiar BLAP discovered by the Tsinghua University - Ma Huateng Telescopes for Survey (TMTS), TMTS J035143.63+584504.2 (TMTS-BLAP-1). This new BLAP has an 18.9 min pulsation period and is similar to the BLAPs with a low surface gravity and an extended helium-enriched envelope, suggesting that it is a low-gravity BLAP at the shortest-period end. In particular, the long-term monitoring data reveal that this pulsating star has an unusually large rate of period change, P_dot/P=2.2e-6/yr. Such a significant and positive value challenges its origins from both helium-core pre-white-dwarfs and core helium-burning subdwarfs, but is consistent with that derived from shell helium-burning subdwarfs. The particular pulsation period and unusual rate of period change indicate that TMTS-BLAP-1 is at a short-lived (~10^6 yr) phase of shell-helium ignition before the stable shell-helium burning; in other words, TMTS-BLAP-1 is going through a "Hertzsprung gap" of hot subdwarfs.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Hanna Sai
Xiaofeng Wang
Nancy Elias-Rosa
Yi Yang
Jujia Zhang
Weili Lin
Jun Mo
Anthony L. Piro
Xiangyun Zeng
Reguitti Andrea
Peter Brown
Christopher R. Burns
Yongzhi Cai
Achille Fiore
Eric Y. Hsiao
Jordi Isern
K. Itagaki
Wenxiong Li
Zhitong Li
Priscila J. Pessi
摘要： Early-time radiative signals from type Ia supernovae (SNe Ia) can provide important constraints on the explosion mechanism and the progenitor system. We present observations and analysis of SN 2019np, a nearby SN Ia discovered within 1-2 days after the explosion. Follow-up observations were conducted in optical, ultraviolet, and near-infrared bands, covering the phases from \sim-16.7 days to \sim+367.8 days relative to its B-band peak luminosity. The photometric and spectral evolutions of SN 2019np resembles the average behavior of normal SNe Ia. The absolute B-band peak magnitude and the post-peak decline rate are M_{\rm max}(B)=-19.52 \pm 0.47mag and \Delta m_{\rm15}(B) =1.04 \pm 0.04mag, respectively. No Hydrogen line has been detected in the near-infrared and nebular-phase spectra of SN 2019np. Assuming that the ^{56}Ni powering the light curve is centrally located, we find that the bolometric light curve of SN 2019np shows a flux excess up to 5.0% in the early phase compared to the radiative diffusion model. Such an extra radiation perhaps suggests the presence of an additional energy source beyond the radioactive decay of central nickel. Comparing the observed color evolution with that predicted by different models such as interactions of SN ejecta with circumstellar matter (CSM)/companion star, a double-detonation explosion from a sub-Chandrasekhar mass white dwarf (WD), and surface ^{56}Ni mixing, the latter one is favored.
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