Pulsar Surveys at Arecibo

Julia Deneva

SDSS, 16 July 2013

AO327 Drift Survey

• All-sky (DEC of -1 to 38deg), excluding +/-5deg from the Galactic plane.

• Pulsars are high-velocity objects; old pulsars may be found far from the Gal. plane, where they formed.

• Millisecond pulsars (MSPs) are old, found mostly in binaries, and have accreted material from a companion, speeding up to P ~ 1.39 – 15ms.

• MSPs are the most accurate natural clocks—tools for gravitational wave detection, tests of GR and alternative theories of gravity, studying the equation of state of neutron star matter.

• Complete models of Galactic pulsar population (so far have only models of disk population).

Why Drift?

• Most efficient way to cover large sky area—beam width is 15’ at 327MHz (vs. 3.5’ at 1420MHz)

• Maximum transit time is 1 minute at 327 MHz; good sensitivity – Pulsars are brighter at low frequencies, S ~ fα, α = -1.7 on average.

• Low-maintenance (operators do most of the observing via scripts).

• Can observe during repairs, painting of platform, shut-down for hurricane warnings

• … and during hurricanes.

• Proposal says “give us 400 h/yr, plus all telescope time no one else wants or can use”.

Phase I Coverage • Grey: data taken • Yellow: data

processed • Black: known

pulsars • Blue (44):

known detected • Magenta (3):

new pulsars (AO327 Pilot)

• Red (23): new pulsars (AO327)

Galactic plane

J0453+16 (P = 46 ms; binary)

Observed change in Pbary over time (figure by Joey Martinez, UTB)

• Porb ~ 4 days • Eccentricity ~ 0.1 • A sin i ~ 14 lt-s

• Minimum Mc ~ 1.0

Msun • Mean Mc ~ 1.3 Msun

(assuming Mpsr = 1.4 Msun)

• Likely NS-NS binary

J1010+15: P = ?, DM = 42 pc/cc, Rotating Radio Transient (RRAT)

Found in AO327 Pilot (WAPP)

PALFA Galactic Plane Targeted Survey

• ALFA receiver: 7 beams; 1.42 GHz • Region: +/-5deg from Gal. plane • Survey found 116 pulsars so far • Started in 2004, ongoing

The ALFA Receiver Power Pattern

• 7 beams, 3.5’ FWHM beam width for each.

• Gain: 10 K/Jy in center beam; 8 K/Jy in side beams

• Have to interleave adjacent 7-beam pointings for tiling the sky.

• 7x the sky area per unit time compared to single-pixel receiver.

• RFI excision via comparing pulsar candidate lists for all beams of a pointing.

Searching in the Galactic plane

• A lot more ionized gas more dispersion and scattering, which broaden pulses and decrease their amplitude, making pulsar detection difficult.

• Dispersion broadening ~ f-2

• Scattering broadening ~ f-4

– Have to use higher frequency when searching in the Gal. plane.

• More pulsars per unit sky area covered statistically more likely to find a few exotic objects (still searching for PSR-BH binary).

• Improving disk population models.

• Improving models of Galactic gas distribution based on pulsar dispersion and scattering measurements.

PALFA Discoveries

• Now up to 116 new pulsars

• 17 MSPs

• 8 Rotating Radio Transients—RRATs (sporadic pulses only)

• 3 young pulsars

• 23 pulsars found by Einsten@Home in PALFA data

J1901+02 (P = 0.885 s; isolated)

J1901+02 (P = 0.885 s; isolated)

J1906+0746 (P = 0.144 s; binary)

J1906+0746 (P = 0.144 s; binary)

• Porb = 3.98 h

• Char. age = 112 kyr (τc = P/2P’)

• PALFA Tobs ~ 2min pulsar discovered

• Parkes Tobs ~ 35min acceleration + Doppler effect due to orbital. motion causes rapid changes in P; was in data but cand SNR was low.

• Have to do FFT + acceleration search to detect tight binaries.

(Parkes survey archival observation)