Abstract
ABSTRACT We report the follow-up of 10 pulsars discovered by the Five-hundred-metre Aperture Spherical radio-Telescope (FAST) during its commissioning. The pulsars were discovered at a frequency of 500-MHz using the ultrawide-band (UWB) receiver in drift-scan mode, as part of the Commensal Radio Astronomy FAST Survey (CRAFTS). We carried out the timing campaign with the 100-m Effelsberg radio-telescope at L-band around 1.36 GHz. Along with 11 FAST pulsars previously reported, FAST seems to be uncovering a population of older pulsars, bordering and/or even across the pulsar death-lines. We report here two sources with notable characteristics. PSR J1951+4724 is a young and energetic pulsar with nearly 100 per cent of linearly polarized flux density and visible up to an observing frequency of 8 GHz. PSR J2338+4818, a mildly recycled pulsar in a 95.2-d orbit with a Carbon–Oxygen white dwarf (WD) companion of $\gtrsim 1\, \rm {M}_{\odot }$, based on estimates from the mass function. This system is the widest WD binary with the most massive companion known to-date. Conspicuous discrepancy was found between estimations based on NE2001 and YMW16 electron density models, which can be attributed to underrepresentation of pulsars in the sky region between Galactic longitudes 70° < l < 100°. This work represents one of the early CRAFTS results, which start to show potential to substantially enrich the pulsar sample and refine the Galactic electron density model.
Highlights
Pulsars are a type of rotating neutron star (NS) that emit beams of electromagnetic radiation along their magnetic axis
Our parameter space is significantly reduced when compared with blind surveys due to the prior information about the pulsar, such as position, dispersion measure (DM), and spin period
We identify four main surveys: AO327 carried by Arecibo Observatory (AO) at a central frequency of 327 MHz (Deneva et al 2013); GBT350 (Hessels et al 2008) and GBNCC (Stovall 2013), both carried with the Green Bank Telescope (GBT) at a central frequency of 350 MHz; and Low-Frequency Array (LOFAR)’s LOTAAS survey at a central frequency of 135 MHz (Sanidas et al 2019)
Summary
Pulsars are a type of rotating neutron star (NS) that emit beams of electromagnetic radiation along their magnetic axis. Pulsar searching is a key component of CRAFTS, along with HI imaging, HI galaxies, and transients. Large-scale commensal survey of HI and pulsars has never been done before CRAFTS, mainly due to HI-imaging requiring a regular injection of an electronic calibration signal to calibrate out short-time-scale gain variation. Such a calibration will pollute the power spectrum with its harmonics and render new pulsars (periodical signals) hard to detect. Pilot CRAFTS scans started in the middle of 2017 during the commissioning phase of FAST, with an un-cooled receiver, namely the Ultra-Wide-Band receiver (UWB: 270 MHz – 1.62 GHz), which was proposed by Li & Pan (2016) and Li et al (2013). More than 120 new pulsars have been confirmed by CRAFTS1 to date
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