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The FAST Galactic Plane Pulsar Snapshot survey

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has the largest collecting area for radio waves, with an illumination area of 300m in diatemter and the aperture efficiency about 60%. Amounted with the 19-beam L-band (1000 - 1500MHz) receivers which have with a system temperature of about 20 K at the primary focus, it is the most sensitive radio telescope over the world. It has excellent performance on pointing, with an uncertainty of less than 8 arcseconds in general (see Jiang et al 2020), and can track a source for a few hours with a full gain in a zenith angle of less than 26 degree. This can further improve the sensitivity with integration time.

Fig.1: The four steps of beam-switching for the 19 beams of the L-band receivers of the FAST can completely cover a sky area for a survey.

Considering that the 19-beam receiver can be slightly moved in the beam-switching mode, every step of such beam-switching costs only or 20 seconds, we therefore designed and successfully tested the snapshot mode in March 2019 so that the four steps of small movements of the feeds make the four pointings which make observations to completely cover a sky area of 0.157 square degree, as seen in Fig.1.

Based on this high efficiency snapshot mode observations, for the risk-share open session of the FAST in 2019, we designed the the Galactic Plane Pulsar Snapshot (GPPS) survey. The goal of the GPPS survey is to make the most sensitive pulsar survey on the Galactic plane in +-5 degree of the Galactic latitudes with the highest priority, and later the survey will extend to +-10 degree (see Fig.2 and Fig.3). The integration time for each pointing is 5 minutes (i.e. 300 seconds). A cover can be surveyed by the 4 pointings made by the beam-switching, which costs 21 minutes in total, including 4*5 minutes for pointing plus 3*20 seconds for beam-switching. It is expected to discover about 1000 pulsars in this sky region of the Galactic plane visible by the FAST. The best wishes include the discovery of pulsars with extremely short rotating periods or extremely short orbit periods if they are in binary.

Fig.2: The pulsar distribution in the sky and the Galactic plane visible to the FAST.

We carried out a series of test observations. Initial efforts were dedicated to examine the data acquisition system and test the pointing accuracy, and to design the data convert software. We designed and later continuously improved the pipelines for data-processing. Radio frequency interference (RFI) has been excused various method, such as ArPLS-ST. We discovered some pulsars in 2019. At the end of 2019, the GPPS project has been officially accepted by the Science Committee of the FAST, as one of five hi-priority major projects of the FAST.

Fig.3: The covers of GPPS survey to observe: observation progress.

Since 2019 March, extensive observations have been made (see Fig.3), and we have already detected several hundreds of known pulsars, and have discovered many new pulsars.

A list of newly discovered pulsars by the GPPS survey
A list of some known pulsars detected by the GPPS survey

You are very welcome to use the GPPS data for your studies or study the GPPS pulsars.

If you want to do such a study or you have any data coincidentally for the new pulsars just discovered here,
please do contact us to avoid any conflict of interest and to make proper acknowledgments or citations.

The GPPS Publications:
1) Han J.L. et al, 2021, The FAST Galactic Plane Pulsar Snapshot Survey: I. Project Design and Pulsar Discoveries, RAA, submitted.
2) Zeng Q.G. et al. 2021, Radio frequency interference mitigation based on the asymmetrically reweighted penalized least squares and SumThreshold method, MNRAS vol. 500, p.2969

The GPPS survey team consists of Prof. JinLin Han (PI,, NAOC),
Chen Wang (NAOC), PengFei Wang (NAOC), Tao Wang (NAOC),
DeJiang Zhou (NAOC), Xue Chen (NAOC), Yi Yan (NAOC), WeiCong Jing (NAOC), WeiQi Su (NAOC),
Peng Jiang (NAOC), JingHai Sun (NAOC), DongJun Yu (NAOC),
RenXin Xu (PKU), KJ Lee (PKU), JinChen Jiang (PKU), YunPeng Men (PKU),
Heng Xu (PKU), ChunFeng Zhang (PKU), BoJun Wang (PKU), JiangWei Xu (PKU),
HongGuang Wang (GZU), WenJun Huang (GZU),
XiaoPeng You (SWU),
JianPing Yuan (XAO), Rai Yuen (XAO), JinTao Xie (XAO), ShuangQiang Wang (XAO).

J.L. Han @2021.04.01