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Candi2 - LOFAR Discovers a Pulsar in a Targeted Search of the 3C196 EOR Field

Submitter: Vlad Kondratiev, Ger de Bruyn, Jason Hessels, Vibor Jelic, Michiel Brentjens, Cees Bassa, and Vishambhar Pandey
Description: PSR J0815+4611, or "Candi2" is the 13th pulsar (a "baker's dozen") discovered with LOFAR, and it's the first found in a targeted search.

It was first identified by Ger de Bruyn in the deep EOR observations of the 3C196 field as a point source with very high polarisation fraction (∼50%) and steep spectrum (index < -2.5). It was named "Candi2" following after Ger's first "Candi" - the famous discovery of the 2.3-ms pulsar J0218+4232 detected in WSRT imaging data through its steep spectrum and high fractional polarisation (Navarro, de Bruyn, Frail et al. 1995, ApJ, 455, 55).

We performed the follow-up 1-h HBA observation with the full core tied-array beam. We searched the dedispersed data for periodic and single-pulse signals and to our excitement we found the pulsar! It's a long-period pulsar with the period P = 434 ms and dispersion measure of 11.28 pc/cm^3; the latter corresponds to a distance of only about 400 pc. From the beamformed data we derived a rotation measure of +3.35 rad/m^2, a high fraction of linear polarisation (>50%), a mean flux density of about 8 mJy, and a very steep spectral index of -2.6. These parameters all agree precisely with what was previously inferred from the EOR images. Thus, the pulsar must be Candi2!

The left figure shows the polarimetric image at a Faraday depth of +3.5 rad/m^2 (uncorrected for ionosphere). Candi2 is in the middle with other diffuse features being from polarised Galactic foreground emission with a similar Faraday depth. On the right is the diagnostic plot from our pulsar search, showing the pulse profile (repeated twice) as a function of time and frequency.

All the LOFAR pulsar discoveries so far can be found on the LOFAR Tied-Array All-Sky Survey (LOTAAS) web-page here.
Copyright: Vlad Kondratiev
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