Pulsar Surveys at Arecibo - Arecibo...
Transcript of Pulsar Surveys at Arecibo - Arecibo...
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Pulsar Surveys at Arecibo
Julia Deneva
SDSS, 16 July 2013
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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).
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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”.
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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
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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
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J1010+15: P = ?, DM = 42 pc/cc, Rotating Radio Transient (RRAT)
Found in AO327 Pilot (WAPP)
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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
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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.
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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.
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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
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J1901+02 (P = 0.885 s; isolated)
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J1901+02 (P = 0.885 s; isolated)
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J1906+0746 (P = 0.144 s; binary)
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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)