1. Part-time pulsarS on behalf of PALFA Collaboration
Vicky Kaspi, McGill University
Professor of Physics,
Director, McGill Space Institute
on behalf of PALFA Collaboration
Lyne et al. 2017, Astrophysical Journal

2. Radio Pulsars Rapidly rotating, highly magnetized neutron stars
Cosmic “lighthouses”: regular radio pulsations
Slow down over time
Over 2500 known in our Milky Way galaxy
Excellent clocks

3. PALFA Pulsar Survey
Large-scale survey for radio pulsars in disk of Milky Way
~2 dozen astronomers from around the world
~175 radio pulsars found so far
Also discovered one Fast Radio Burst
Only known repeater
Discussed in 11:15 am press conference today

4. Arecibo Discovery of Two “Part-Time” Pulsars
Two new PALFA pulsars are unusual: they are off most of the time!
PSR J : on only 30% of the time!
PSR J : on only 0.8% of the time!
Later changed to 16% of the time
Pulsars studied intensively at Jodrell Bank Observatory in UK

5. Radio Pulsar Vanishing Act!
Number of Observations
Radio Intensity
Radio Intensity

6. Implications I Spin-down Rate On Fraction
PSR J
Radio emission mechanism can turn on/off
Affects spin-down rate:
pulsars spin down faster when ‘on’
Close relationship between slow-down forces and radio emission
Surprising as radio tiny fraction of pulsar energy budget
Spin-down Rate
On Fraction

7. Implications II Must be many more pulsars like these
For on-fraction 1%, we detected only 1/100 !
Worse, has hard to confirm a detection
Implies known Milky Way radio pulsar population more incomplete than thought!
Difficult to estimate how many yet unseen

8. Recap: Arecibo Discovery of Two Intermittent Radio Pulsars
Arecibo PALFA radio pulsar survey ongoing
Discovered two highly intermittent pulsars
Are off most of the time!
Shed new light on pulsar physics
Imply many radio pulsars yet unseen