Having achieved 'first-light' right before the opening ceremony on September 25, 2016, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is now kept busy with commissions. Its innovative design requires ~1,000 points to be measured and driven instead of just the two axes of motion, e.g. Azimuth and Elevation for most of the conventional antennae, to realize pointing and tracking. We have devised a survey plan to utilized the full sensitivity of FAST, while minimizing the complexities in operation the system. The 19-beam L band focal plan array will be rotated to specific angles and taking continuous data streams while the surface shape and the focal cabin stay fixed. Such a survey will cover the northern sky in about 220 full days. Our aim is to obtain data for pulsar search, HI (neutral hydrogen) galaxies, HI imaging, and radio transients, simultaneously, through multiple backends. These data sets could be a significant contribution to all related fields in radio astronomy and remain relevant for decades.
Publications:
FAST in Space: Considerations for a Multibeam, Multipurpose Survey Using China's 500-m Aperture Spherical Radio Telescope (FAST)
Di Li; Pei Wang; Lei Qian; Marko Krco; Alex Dunning; Peng Jiang; Youling Yue; Chenjin Jin; Yan Zhu; Zhichen Pan; and Rendong Nan;
IEEE Microwave Magazine, Volume 19, Issue 3, pp.112-119 ADS Link
News:
We report the discovery of an eclipsing binary millisecond pulsar in the globular cluster M92 (NGC6341) with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). PSR J1717+4308A, or M92A, has a pulse frequency of 316.5~Hz (3.16~ms) and a dispersion measure of 35.45 pc cm$^{-3}$. The pulsar is a member of a binary system with an orbital period of 0.20~days around a low-mass companion which has a median mass of $\sim$0.18~\Ms. From observations so far, at least two eclipsing events have been observed in each orbit. The longer one lasted for ~5000~s in the orbital phase range 0.1--0.5. The other lasted for ~500~s and occurred between 1000--2000~s before or after the longer eclipsing event. The lengths of these two eclipsing events also change. These properties suggest that J1717+4308A is a ``red-back'' system with a low-mass main sequence or sub-giant companion. Timing observations of the pulsar and further searches of the data for additional pulsars are ongoing.
Figure 1. -- M92A eclipses. Left: folding result of FAST data taken on 2018 September 13th. The short eclipse event happened two thousand seconds before the longest eclipse (at the beginning of the observation). Middle: folding result of FAST data taken on 2018 October 2nd. The short eclipse event happened approximately one thousand seconds after the longest eclipse. Right: folding of GBT data taken on 2018 June 29th to 30th, showing the huge sensitivity difference between GBT and FAST.
Figure 2. -- shows Timing residuals as a function of orbital phase and the mean pulse profile.
ATel Link
Tracking observations of FRB 121102 were carried out with the newly commissioned Five-hundred-meter Aperture Spherical radio Telescope (FAST). We used the FAST L-band Array of 19-beams (FLAN), which has a FWHM of ~2.95' for individual beams and a ~26' footprint. The source was placed in the central beam, while all 19 beams were recorded. The bursts were firstly identified by the FRB backend on August 29th (UT), which performs real time signal processing of 19-beams data and automatic candidate selection/triggering. The subsequent single pulse search using multiple pipelines have turned up many tens of pulses with significant SNR in observations carried out so far, on the 29th, 30th, and 31st (UT). While careful cross-check are being carried out, the majority of these detections are expected to be credible. FAST has been targeting FRB 121102 since April of this year. In addition to the regular on-going FRB follow-up programs, the current observations was also motivated by timely and valuable alerts from our colleagues in the INTEGRAL team, Arecibo team, Max-Plank Institute for Radio Astronomy, Berkeley, and Cornell University. Given the significance of this source and its now apparent active state, FAST is executing more observations under the auspice of engineering testing time and multiple approved PI-led programs, which targeted FRB 121102. We encourage more ToO observations with other facilities.
(pulse from FRB121101)
FAST's First Discovery of a Millisecond Pulsar (MSP)
On 27 Feb. 2018, the Five-hundred-meter Aperture Spherical radio Telescope (FAST), operated by the National Astronomical Observatories, Chinese Academy of Sciences, discovered a radio millisecond pulsar (MSP) coincident with the unassociated gamma-ray source 3FGL J0318.1+0252 in the Fermi Large Area Telescope (LAT) point-source list. It was confirmed by the Fermi-LAT team in reprocessing of Fermi data on April 18th. This is another milestone of FAST.
Radio follow-up of Fermi-LAT unassociated sources is one of the effective ways for finding new pulsars. Previous radio observations, including three epochs with Arecibo in June 2013, failed to detect the MSP. In an one-hour tracking observation with the FAST ultra-wide band receiver, the radio pulses toward 3FGL J0318.1+0252 were detected with a spin period of 5.19 milliseconds, an estimated distance of about 4 thousand light-years, and as potentially one of the faintest radio MSPs. The newly discovered pulsar, now named PSR J0318+0253, is confirmed to be isolated through timing of gamma-ray pulsations. This discovery is the first result from the FAST-Fermi LAT collaboration outlined in a MoU signed between the FAST team and Fermi-LAT team.
Millisecond pulsars is a special kind of neutron stars that rotate hundreds of times per second. It is not only expected to play an important role in understanding the evolution of neutron stars and the equation of state of condense matter, but also can be used to detect low-frequency gravitational waves. The pulsar timing array (PTA) attempts to detect low-frequency gravitational waves from merging supermassive black holes using the long-term timing of a set of stable millisecond pulsars. Pulsar search is the basis of gravitational wave detection. The planned Commensal Radio Astronomy FAST Survey (CRAFTS, arxiv:1802.03709; http://localhost/) is expected to discover many millisecond pulsars and thus will make significant contribution to the PTA experiment.
Kejia Lee, a staff scientist at the Kavli Institute of Astronomy and Astrophysics, Peking University, said that “This discovery demonstrated the great potential of FAST in pulsar searching, highlighting the vitality of the large aperture radio telescope in the new era. It is a great achievement fo FAST, still under commissioning. (He) looks forward to its full operation soon.”
Renxin Xu, a professor of astronomy at Peking University, said that “Besides their scientific significance, millisecond pulsars also have potential value in other applications. MSP discoveries from FAST will provide better opportunities for scientists and engineers around the world.”
George Hobbs, a staff scientist of the Commonwealth Scientific and Industrial Research Organisat (CSIRO)of Australia and a member of the Gravitational Wave International Committee (GWIC), said “The international radio-astronomy community is excited about the amazing FAST telescope. The Australian Parkes Telescope helped confirm FAST’s first pulsar discovery and now Fermi Space Observatory is instrumental in FAST’s first millisecond pulsar. FAST will soon discover a large number of millisecond pulsars and I am looking forward to seeing FAST’s contribution to gravitational wave detection.”
FAST will be under commissioning until it reaches the designed specifications and becomes a Chinese national facility.
Fig1. The Gamma-ray sky map and integrated pulse profiles of the new MSP:
Upper panel shows the region of the gamma-ray sky where the new MSP is located.
Lower panel a) shows the observed radio pulses in a one-hour tracking observation of FAST.
Lower panel b) shows the folded pulses from more than 9 years of Fermi-LAT gamma-ray data.
