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| 1 | The FAST Galactic Plane Pulsar Snapshot survey:I.Project design and pulsar discoveries显示文摘Discovery of pulsars is one of the main goals for large radio telescopes.The Five-hundredmeter Aperture Spherical radio Telescope(FAST),that incorporates an L-band 19-beam receiver with a system temperature of about 20 K,is the most sensitive radio telescope utilized for discovering pulsars.We designed the snapshot observation mode for a FAST key science project,the Galactic Plane Pulsar Snapshot(GPPS)survey,in which every four nearby pointings can observe a cover of a sky patch of 0.1575 square degrees through beam-switching of the L-band 19-beam receiver.The integration time for each pointing is 300 seconds so that the GPPS observations for a cover can be made in 21 minutes.The goal of the GPPS survey is to discover pulsars within the Galactic latitude of±10∘from the Galactic plane,and the highest priority is given to the inner Galaxy within±5∘.Up to now,the GPPS survey has discovered 201 pulsars,including currently the faintest pulsars which cannot be detected by other telescopes,pulsars with extremely high dispersion measures(DMs)which challenge the currently widely used models for the Galactic electron density distribution,pulsars coincident with supernova remnants,40 millisecond pulsars,16 binary pulsars,some nulling and mode-changing pulsars and rotating radio transients(RRATs).The follow-up observations for confirmation of new pulsars have polarization-signals recorded for polarization profiles of the pulsars.Re-detection of previously known pulsars in the survey data also leads to significant improvements in parameters for 64 pulsars.The GPPS survey discoveries are published and will be updated at http://gffzz656c80eee53645cchqbwn6609o9no65xb.ffgz.tsg.suse.edu.cn/GPPS/. | J.L.Han Chen Wang P.F.Wang Tao Wang D.J.Zhou Jing-Hai Sun Yi Yan Wei-Qi Su Wei-Cong Jing Xue Chen X.Y.Gao Li-Gang Hou Jun Xu K.J.Lee Na Wang Peng Jiang Ren-Xin Xu Jun Yan Heng-Qian Gan Xin Guan Wen-Jun Huang Jin-Chen Jiang Hui Li Yun-Peng Men Chun Sun Bo-Jun Wang H.G.Wang Shuang-Qiang Wang Jin-Tao Xie Heng Xu Rui Yao Xiao-Peng You D.J.Yu Jian-Ping Yuan Rai Yuen Chun-Feng Zhang Yan Zhu | 2021 | Research in Astronomy and Astrophysics2021，21，5： | 4 |
| 2 | Targeted Search for Fast Radio Bursts with Nanshan 26m Radio Telescope显示文摘Fast radio bursts(FRBs)are radio transients that are bright and have short duration,with their physical mechanism not being fully understood.We conducted a targeted search for bursts from FRB 20201124A between 2021 June 2and July 20.High time-resolution data were collected for 104.5 hr using the ROACH2-based digital backend.We introduce the details of our FRB search pipeline which is based on HEIMDALL and FETCH.Testing of the injected mock FRBs search could help us better understand the performance of the pipelines,and improve the search algorithms and classifiers.To study the efficiency of our pipeline,5000 mock FRBs were injected into the data and searched using the pipeline.The results of the mock FRB search show that our pipeline can recover almost all(?90%)the injected mock FRBs above a signal-to-noise ratio(S/N)threshold of 15,and the performance is still acceptable(?80%)for injected S/Ns from 10 to 15.The recovery fraction displays relations with S/N,dispersion measure and pulse width.No bursts were detected from FRB 20201124A in the middle of 2021.The non-detection of FRB 20201124A may be due to its quiet phase window or no emission above the threshold of the Nanshan telescope. | Jian-Wei Mao Jian-Ping Yuan Zhi-Gang Wen Jian Li Na Wang Pei Wang Rai Yuen Yu-Bin Wang Nan-Nan Zhai Zhi-Yong Liu Mao-Zheng Chen Guang-Hui Li | 2022 | Research in Astronomy and Astrophysics2022，22，6： | 0 |
| 3 | The Multiple Images of the Plasma Lensing FRB显示文摘We investigate the formation of multiple images as the radio signals from fast radio bursts(FRBs)pass through the plane of a plasma clump.The exponential model for the plasma clump is adopted to analyze the properties of the multiple images.By comparing with the classical dispersion relations,we find that one image has exhibited specific inverse properties to others,such as their delay times at high frequency is higher than that at low frequency,owing to the lensing effects of the plasma clump.We demonstrate that these inverse effects should be observable in some repeating FRBs.Our results predict deviation in the estimated dispersion measure(DM)across multiple images,consistent with the observations of FRB 121102 and FRB 180916.J0158+65.If other plasma lenses have effects similar to an exponential lens,we find that they should also give rise to a similar dispersion relation in the multiple images.For some repeating FRBs,analysis of the differences in time delay and in DM between multiple images at different frequencies can serve as a method to reveal the plasma distribution. | Yu-Bin Wang Zhi-Gang Wen Rai Yuen Na Wang Jian-Ping Yuan Xia Zhou | 2022 | Research in Astronomy and Astrophysics2022，22，6： | 0 |
| 4 | Spin-down and emission variations for PSR J0742-2822显示文摘PSR J0742-2822 is known for its quasi-periodic changes in the observed pulse profile and spindown rate.In this paper,we analyzed 13 years of timing data obtained with the Nanshan 25-m radio telescope and the Parkes 64-m radio telescope.We found that the average values of the spin-down rate((v))of this pulsar changed in four different states.We investigated the correlation between v and W50,and ascertained that the correlation changed in different states.Moreover,not all the changes in states and correlation can be associated with glitch activities.We examined the long term evolution ofγ-ray flux(0.1-300 GeV)and the pulse profiles corresponding to the four different states using Fermi-LAT Pass8(P8 R3)data from 2008 August 5 to 2019 October 1.We did not detect a significant change inγ-ray flux or the pulse profile.Our results suggest that the connection between pulsar rotation and emission is more complex than previously reported for this pulsar. | Shi-Jun Dang Na Wang Hui-Hui Wang Jian-Ping Yuan Lun-Hua Shang Rai Yuen Ming-Yu Ge Xia Zhou Shuang-Qiang Wang Fei-Fei Kou Wen-Ming Yan Jing-Bo Wang Zhi-Gang Wen Jun-Tao Bai Zhi-Yong Liu Zu-Rong Zhou | 2021 | Research in Astronomy and Astrophysics2021，21，2： | 0 |
| 5 | A Search Technique Based on Deep Learning for Fast Radio Bursts and Initial Results for FRB 20201124A with the NSRT显示文摘The origin and phenomenology of Fast Radio Bursts(FRBs) remain unknown. Fast and efficient search technology for FRBs is critical for triggering immediate multi-wavelength follow-up and voltage data dump. This paper proposes a dispersed dynamic spectra search(DDSS) pipeline for FRB searching based on deep learning, which performs the search directly from observational raw data, rather than relying on generated FRB candidates from single-pulse search algorithms that are based on de-dispersion. We train our deep learning network model using simulated FRBs as positive and negative samples extracted from the observational data of the Nanshan 26 m radio telescope(NSRT)at Xinjiang Astronomical Observatory. The observational data of PSR J1935+1616 are fed into the pipeline to verify the validity and performance of the pipeline. Results of the experiment show that our pipeline can efficiently search single-pulse events with a precision above 99.6%, which satisfies the desired precision for selective voltage data dump. In March 2022, we successfully detected the FRBs emanating from the repeating case of FRB 20201124A with the DDSS pipeline in L-band observations using the NSRT. The DDSS pipeline shows excellent sensitivity in identifying weak single pulses, and its high precision greatly reduces the need for manual review. | Yan-Ling Liu Jian Li Zhi-Yong Liu Mao-Zheng Chen Jian-Ping Yuan Na Wang Rai Yuen Hao Yan | 2022 | Research in Astronomy and Astrophysics2022，22，10： | 0 |
| 6 | Investigation of Mode Changing,Pulse Nulling and Subpulse Drifting Properties in the Asymmetric Conal Triple Radio Pulsar B2319+60显示文摘We report on a detailed analysis of the mode changing,nulling and subpulse drifting behavior of the conal triple pulsar B2319+60 at 1.5 GHz observed with the Nanshan 25 m radio telescope.The pulsar’s profile can be interpreted as resulting from a sightline traverse which cuts across an outer cone and tangentially grazes an inner cone.About 30 per cent of nulls are found to create alternating bunches of nulls and emission in a quasi-periodic manner with an averaged fluctuation rate of about four rotation periods(P_(1)).The presence of two distinct drift modes(A and ABN)plus a phase-stationary non-drift emission mode(B)is confirmed,and each corresponds to a different pulse profile.The mode A is dominated by a phase modulation in the trailing component with a circulation time of around 7P_(1).In addition to a 3P_(1)phase modulation in the leading component,mode ABN presents an amplitude modulation in the leading and trailing components with a period of around 40P_(1).The emission region and geometry remain constant during mode changing.The diversity seen in the individual pulse behavior of the pulsar B2319+60 provides a unique window into the emission physics. | Jian-Ling Chen Zhi-Gang Wen Hong-Guang Wang Na Wang Rai Yuen Vishal Gajjar Jian-Ping Yuan Zhen Wang Wen-Ming Yan Jin-Peng Wang Cheng-Bing Lyu Hui Wang Xue-Feng Duan | 2022 | Research in Astronomy and Astrophysics2022，22，11： | 0 |
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