PARTTIME PULSARS Vicky Kaspi Mc Gill University Professor

PART-TIME PULSARS Vicky Kaspi, Mc. Gill University Professor of Physics, Director, Mc. Gill Space Institute vkaspi@physics. mcgill. ca on behalf of PALFA Collaboration Lyne et al. 2017, Astrophysical Journal

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

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

Arecibo Discovery of Two “Part-Time” Pulsars Two new PALFA pulsars are unusual: they are off most of the time! PSR J 1910+0517: on only 30% of the time! PSR J 1929+1357: on only 0. 8% of the time! Later changed to 16% of the time Pulsars studied intensively at Jodrell Bank Observatory in UK

Number of Observations Radio Pulsar Vanishing Act! Radio Intensity

Implications I pulsars spin down faster when ‘on’ Close relationship between slow-down forces and radio emission Spin-down Rate Radio emission mechanism can turn on/off Affects spin-down rate: PSR J 1929+1357 Surprising as radio tiny fraction of pulsar energy budget On Fraction

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

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