XAO OpenIR

A Single-pulse Study of Three CRAFTS Pulsars Discovered with FAST

2026-06-04T11:07:24Z

Title: A Single-pulse Study of Three CRAFTS Pulsars Discovered with FAST Authors: Rejep, R.; Zhu, W. W.; Wang, N.; Yan, W. M.; Yuan, J. P.; Wu, Q. D.; Gugercinoglu, E.; Wang, W. Y. Description: We present a comprehensive single-pulse study of three pulsars, namely PSRs J1854-0036, J2159+0202, and J2112+0740, discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal Radio Astronomy FAST Survey (CRAFTS). We observe that these pulsars display different kinds of single-pulse phenomena, bearing implications for pulse emission mechanisms and geometry. PSR J1854-0036 exhibits quasiperiodic nulling with a nulling fraction of 31% +/- 1% and a periodicity of (127.4 +/- 0.4)P (where P is the spin period of the pulsar). We identified a weak emission in the null profile, suggesting either a global magnetospheric state switching or a change in geometric orientation rather than complete cessation of emission. PSR J2159+0202 exhibits complex subpulse drifting or intensity modulations with periodicities ranging from P3 = (7.0 +/- 0.2)P to (10.9 +/- 0.1)P. PSR J2112+0740 exhibits burst-like radiation without evidence of nulling or coherent subpulse drifting, potentially associated with stochastic pair production or plasma instabilities within the pulsar's emission region. These results highlight the multiscale nature of the pulsar emission, potentially linking nulling, drifting, and erratic radiation to different magnetospheric processes.

Cold Dust Properties and Submillimeter Excess in 33 Nearby Spiral Galaxies

2026-06-04T10:54:18Z

Title: Cold Dust Properties and Submillimeter Excess in 33 Nearby Spiral Galaxies Authors: Chang, Zhengxue; Zhou, Jianjun; Lamperti, Isabella; Saintonge, Amelie; Zeng, Xiangyun; Wang, Shumin; Esimbek, Jarken; Shi, Ruimin; Qiu, Jianjie; Zhao, Na; He, Yuxin; Li, Qiang; Li, Linlin; Huang, Long; Shen, Hailiang; Liu, Xiaona Description: The origin of submillimeter excess in galaxies remains unclear. We analyze cold dust properties of 33 nearby spiral galaxies, identify a possible 850 mu m excess, and explore its environments. Spectral energy distributions are fitted using a hierarchical Bayesian framework with three modified blackbody models: single temperature (SMBB), two temperature (TMBB), and broken emissivity. With a standard value of the cold dust emissivity index (beta(c) = 2), 13 galaxies exhibit 850 mu m excess using SMBB and TMBB. With decreasing beta(c), the submillimeter excess still persists: at beta(c) = 1.8, 10 (SMBB) and nine (TMBB) galaxies retain the submillimeter excess; at beta(c) = 1.5, six galaxies remain in the submillimeter excess. Even when beta(c) is free, some galaxies still show 850 mu m excess, suggesting the submillimeter excess arises from intrinsic dust properties rather than modeling artifacts. Submillimeter excess correlates with metallicity, being more likely to occur in low-metal galaxies. A low 160-to-850 mu m flux ratio (typically <50-70) may serve as a criteria for selecting candidate galaxies with submillimeter excess. Based on TMBB, cold dust temperature correlates positively with molecular gas fraction ( logM(H2)/M-* ) and specific star formation rate (sSFR). The cold dust emissivity index shows positive correlations with star formation rate, stellar mass, oxygen abundance, and logM(H2)/M-*, and a negative correlation with atomic gas fraction. Cold dust-to-stellar mass ratio correlates positively with gas fraction and sSFR, and anticorrelates with stellar mass. These results provide constraints on the nature of submillimeter excess and physical properties of cold dust in spiral galaxies.

Revealing the Unseen: The Discovery of Long-awaited Radiation from the Intermittent Pulsar PSR B1931+24

2026-06-04T10:54:16Z

Title: Revealing the Unseen: The Discovery of Long-awaited Radiation from the Intermittent Pulsar PSR B1931+24 Authors: Rusul, Abdujappar; Wen, Z. G.; Yuan, J. P.; Esamdin, Ali; Zheng, X. P.; Kramer, Michael Description: Pulsars are typically characterized by their stable, highly magnetized, and fast-rotating nature, which underpins their persistent radio emissions. However, the discovery of prolonged radio-quiet ("off") states in intermittent pulsars, such as PSR B1931+24, has been challenging the fundamental theory of pulsar magnetospheric emission. Despite long-term monitoring with several telescopes over 20 yr, the observations of PSR B1931+24 had not detected any significant emission during its "off" states. Recently, sensitive observations via the Five-hundred-meter Aperture Spherical radio Telescope revealed the mysterious weak emissions containing occasional faint bursting pulses during the "off" states of PSR B1931+24, signifying the theory of pulsar magnetospheric emission that the pulsar cannot remain off for long unless it truly dies. Along with a substantial decrease in flux density, a contraction and change in the integrated pulse profile are measured in the "off" state compared to the radio-loud ("on") state, indicating alterations in the plasma supply and magnetospheric structure. Additionally, previously unobserved asynchronous, nonuniform emission patterns are found in both states, implying a spatially inhomogeneous pair-cascade associated with the coherent radio emission of the pulsar. Furthermore, statistical comparisons between the faint off-state bursts and the on-state emission show that the faint bursts cannot be explained simply as a scaled-down version of the on-state emission. Instead, they constitute a distinct emission mode, plausibly linked to changes in plasma supply and the magnetospheric configuration of PSR B1931+24. These findings greatly advance our understanding of pulsar magnetospheric dynamics and emission mechanisms.

The Overall Emission Arrangement in Four Long-period Pulsars

2026-06-04T10:54:15Z

Title: The Overall Emission Arrangement in Four Long-period Pulsars Authors: Yuen, Rai Description: Investigation of the overall emission arrangement in the emission region for four long-period pulsars is conducted by comparing the differences between their observed and predicted profile widths. The observed profile widths are taken from results based on observations with the Five-hundred-meter Aperture Spherical radio Telescope, whereas the predicted widths are derived from the conventional viewing geometry. The geometry predicts a profile width defined by emission coming from all the source points along a trajectory that traverses within an open-field region at certain height. In contrast, the observed profile width corresponds to only the range of the same open-field region cut by the trajectory that is actually detectable to the observer, referred here as the observable emission region. Our results show that the observable emission regions tend to coincide with the open-field regions, and their centers also exhibit a tendency to align, meaning that the emission originates around the magnetic pole. We demonstrate that the emission structure is likely uniform in the open-field region at a large rotation period. The field lines are mostly dipolar, and the radio emission is confined within the open-field region.

Upper Limits on Microhertz Gravitational Waves from Supermassive Black Hole Binaries Using PSR J1909-3744 Data from the Second IPTA Data Release

2026-06-04T10:54:13Z

Title: Upper Limits on Microhertz Gravitational Waves from Supermassive Black Hole Binaries Using PSR J1909-3744 Data from the Second IPTA Data Release Authors: Zou, Jing; Wang, Jingbo; Yuan, Jianping; Zhao, De; Wen, Yirong; Li, Wei; Wang, Na; Xia, Yong Description: We present the results of a search for gravitational waves (GWs) from individual sources using high-cadence observations of PSR J1909-3744 obtained during an intensive observing campaign with the International Pulsar Timing Array second data release between 2010 July and 2012 November. The observations, conducted at three different radio frequencies with the Nan & ccedil;ay Radio Telescope and Parkes Telescope and five frequencies with the Green Bank Telescope, enabled precise corrections for dispersion measure effects and scattering variations. After these corrections, the timing residuals showed an unmodeled periodic noise component with an amplitude of 340 ns. Our analysis yields upper limits on the GW strain from individual sources, constraining it to be below 1.9 & times; 10-14 at 71 nHz and 2.3 & times; 10-13 at 1 mu Hz for average sky locations, while for optimal source locations, the limits improve to 6.2 & times; 10-15 and 8.9 & times; 10-14 at the same frequencies, respectively. Our new limits are about a factor of 1.52 more stringent than those of B. B. P. Perera et al. (2018) based on an earlier EPTA data.

The Determination of Relaxed Deformation Error for Large Antennas Main Reflector Compensated by Shaped Subreflector

2026-06-04T10:54:11Z

Title: The Determination of Relaxed Deformation Error for Large Antennas Main Reflector Compensated by Shaped Subreflector Authors: Ban, You; Wang, Na; Xu, Qian; Feng, Shufei; Duan, Baoyan Description: A determining method of relaxed deformation error for large antennas main reflector that considers the compensation of the shaped subreflector is proposed. Using the orthogonal functions, describe the independent error items of antennas' reflector that make it universal, and combining the approximate electrical field calculation and the compensation functions of shaped subreflector establish the relaxed error determination model for main reflector deformation. To solve the model that includes internal and external optimization, the path length error iterative compensation method is used to fast design the shaped subreflector. And for the external optimization, a dichotomy, taking into account the monotonic relationship between reflectors error and antennas gain, is designed to iteratively obtain the relaxed error items' upper, lower bounds and the convergent results. The 110 m standard and 80 m offset reflector antennas working at 115 and 30 GHz, respectively, with two classic deformation error types, are taken as examples. The excellent results obtained by a few iterations showed the effectiveness of the proposed model and the corresponding fast solution method, and both types of the two type errors are relaxed by over tens and even hundreds of times, indicating the enormous potential of the shaped subreflector for compensating the main reflector deformation.

The Lower Shire Karoo Basin architecture using 3-D gravity inversion modelling

2026-06-04T10:54:09Z

Title: The Lower Shire Karoo Basin architecture using 3-D gravity inversion modelling Authors: Manda, Brave; Yan, Jianguo; Dulanya, Zuze; Chisenga, Chikondi Description: We studied the Ngabu sub-basin to determine its three-dimensional (3-D) structure and geometry using a depthweighted gravity inversion approach. The Ngabu sub-basin is part of the Shire Graben within the Western Branch of the East African Rift System, located in southern Malawi, southeastern Africa. This region has been identified as a potential hydrocarbon exploration area due to its rifting history and tectonic evolution. The objectives of this study are to (1) develop three-dimensional density structures, (2) characterize the basin architecture and geometry, and (3) constrain the depth. The resolved 3-D density structures reveal that the Ngabu sub-basin depocenter extends to approximately 4 km in depth. It is separated from the Mwabvi sub-basin by a highdensity structure, likely linked to magmatic activity associated with the formation of the Chikwawa Basalts. The Nyamalambo and Nkombedzi faults appear near the edges of the airborne gravity data coverage, while the Mwanza and Thyolo faults are interpreted to extend to depths of similar to 4 km. These major faults significantly influence sediment distribution and the landscape within the Shire Rift Valley. Despite data limitations affecting the full resolution of the Lengwe and Mwabvi sub-basins, low-density anomalies suggest that the Lengwe and Ngabu sub-basins are the largest and trend NW-SE, while the Mwabvi sub-basin is smaller and structurally distinct. The low-density structures also suggest the presence of a possible Karoo outlier related to the Ngabu subbasin, which may have originally formed as part of a unified basin before being segmented by magmatic activity during Middle Jurassic-Cretaceous magma-rich rifting. The methodological approach utilized in this study can be applied in other sedimentary environments in the Western Branch of the East African Rift System to understand the Karoo basin architecture, sedimentary thickness, and geometry.

An Artificial Pulsar-signal Generator for Pulsar Search

2026-06-04T10:54:07Z

Title: An Artificial Pulsar-signal Generator for Pulsar Search Authors: Yu, Yun; Gu, Junhua; Guo, Quan; Yang, Jun; Zhou, Zurong; Hu, Yue; Zhao, Chengshi; Li, Peng; Zhao, Bixuan Description: Pulsars, which are spinning neutron stars emit regular pulses and are essential to time-domain radio astronomy. Numerous observatories concentrate on detecting and researching faint pulsar signals, especially at radio frequencies. To enable rapid system verification, optimization, and troubleshooting, we have devised a cost-effective artificial pulsar signal generator utilizing an economical software-defined radio. These artificial signals are digitally synthesized with customizable parameters such as pulse period, dispersion measure, central frequency, bandwidth, sampling rate, pulse duration, and noise level. The central frequency can be set within 70 MHz-6 GHz, the instantaneous bandwidth up to 56 MHz, and the output power controlled via the gain setting, typically ranging from -20 to +10 dBm depending on frequency and gain. By incorporating frequency-dependent dispersion delays and Gaussian noise, these simulated signals can replicate the time and spectral features of actual pulsar emissions in a laboratory setting. Additionally, we performed single-dish experiments using the simulated pulsar signal and the 40 m radio telescope at Haoping Station, China. The resulting data were processed with standard pulsar signal analysis software. This demonstrates the signal generator's precision in fulfilling system calibration and verification needs for pulsar observations. As an affordable and compact device, the pulsar signal simulator enables researchers to design and experiment with new-generation pulsar backends anywhere and at any time without relying on a strong pulsar source. Moreover, it offers astronomers the opportunity to engage in pulsar-related educational activities using a small antenna at frequencies <6 GHz.

Research on Multimodal RFI Cancellation in QTT-PAF Beamforming Based on the PCA Algorithm

2026-06-04T10:54:05Z

Title: Research on Multimodal RFI Cancellation in QTT-PAF Beamforming Based on the PCA Algorithm Authors: Qi, Yi-Fan; Pei, Xin; Wu, Peng; Zhang, Ke; Lian, Pei-Yuan; Yan, Yue-Fei; Wang, Cong-Si Description: This study tackles the multimodal radio frequency interference (RFI) challenges encountered by the Qitai Radio Telescope by developing a comprehensive numerical model. The model integrates four critical interference types: coupling effects, fixed-position interference, moving-position interference, and white noise. These interferences exhibit dynamic variations in both temporal and spatial domains. Innovatively, this work introduces the principal component analysis (PCA) algorithm to beamforming for the first time, conducting a systematic performance comparison with the conventional subspace projection (SP) algorithm. The interference cancellation capability of PCA is rigorously evaluated under two scenarios: (i) complete spatial separation between signal of interest (SOI) and RFI, and (ii) partial or full spatial overlap between SOI and RFI distributions. Results demonstrate that PCA achieves a 30 dB S/N improvement over SP while maintaining the same robust coupling effects as SP. Crucially, PCA better handles overlapping SOI-RFI scenarios, in which traditional methods exhibit significant performance degradation. This research provides a foundational framework for future beamformer design, offering significant potential to advance RFI mitigation technologies and enhance the observational robustness of radio telescopes in complex electromagnetic environments.

Holographic dark energy in a coasting cosmology

2026-06-04T10:54:03Z

Title: Holographic dark energy in a coasting cosmology Authors: Ren, Yunliang; Yang, Xiaofeng; Zhang, Xuwei; Chen, Shuangnan; Shi, Yangjun; Cheng, Cheng; He, Xiaolong; Iminniyaz, Hoernisa Description: Coasting cosmology offers an intriguing and straightforward framework for understanding the universe. In this work, we employ the Trans-Planckian Censorship Criterion (TCC) conjecture to test the viability of the coasting cosmology and propose an entropic dark energy (EDE) model within this framework. By applying the holographic principle to constrain the dark energy density and adopting the Bekenstein entropy and Tsallis entropy as the constraining entropies of the system, we find that, in a holographic coasting cosmological framework where dark energy and dark matter evolve independently, the Tsallis entropy satisfies certain general assumptions better than the Bekenstein entropy. Thus, there may be a fundamental relationship between Tsallis entropy and dark energy. We utilize observational data from Type Ia Supernovae (SNIa), Baryon Acoustic Oscillations (BAO), and Cosmic Chronometers (CC) to constrain EDE model. The optimal Tsallis parameter obtained aligns well with theoretical expectations. To evaluate the model's fit to the observed data, we calculate the Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), and Kullback Information Criterion (KIC), and compare these metrics with those derived from Lambda CDM, under which the model shows some improvement. Overall, this model provides a novel and simple on the evolution of the universe.