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Kevin Stovall NRAO
IPTA 2018 Student Workshop, 11 June, 2018
Pulsar Overview
Pulsars
Pulsars
• ~2,700 pulsars known
• Act as clocks, therefore provide a means for studying a variety of physical phenomena
• Strongly affected by the interstellar medium (ISM)
• There are many categories of pulsars (MSPs, RRATs, DNSs, mode-switching, nulling, etc.)
• As a population are steep spectrum sources (alpha~-1.4)
Some Pulsar Applications Populations
•Neutron Stars •Supernovae / Massive Stars •Binaries •Millisecond Pulsars (MSPs)
Exotic Systems•Double Neutron Stars (DNSs) •Triple Systems •Double Pulsar •Pulsar-BH
Clocks•Time Standard
Study of Interstellar Medium•Dispersion •Scattering/Scintillation •Faraday rotation
Extreme Environments•Large B-field •Neutron Star Interior •Tight Binary systems •Fast Spinning
Theories of Gravity•Tests of GR •Alternative Theories •Gravitational Waves
Pulsars
Pulse “Folding”
Interstellar Medium Effects
From “Essential Radio Astronomy”, Condon & Ransom
DM =R d0 nedl
Delay / DM ⌫�2
Dispersion
Galactic Electron Density
Yao, Manchester & Wang, 2017, ApJ, 835Lazio & Cordes, 2002, astro-ph:0207156
Scintillation Arcs
From “Handbook of Pulsar Astronomy”, Lorimer & Kramer
Scattering Scintillation
ISM: Faraday rotation� PPA = –2 ⇥ RM
RM = e3
2ım2ec
4
R d0 neB||dl
hB||i = 1:23—G RMDM
Profile Temporal Stability
Pulsar Timing
P-Pdot Diagram
Millisecond Pulsars (MSPs)
• Spin periods less than ~10 ms, weaker magnetic fields, smaller spin-down rates
• Formed through accretion from a companion star (therefore most of them are in binaries: 2/3)
mildly recycled pulsar
X-rays
runaway star
young pulsar
primary
millisecond pulsar - white dwarf binary
binary disrupts
double neutron star binary
binary disrupts
young pulsar
secondary
binary survives
secondary evolves(Roche Lobe overflow)
binary surviveslow-mass system
Supernova
Supernovahigh-mass system
(b)(a)
Lorimer, 2008, LRR, 11
Pulsar Spatial Distribution
Pulsar Sky Distribution
Pulsar Surveys (partial list)Survey
Center Frequency
(MHz)Bandwidth
(MHz)
Frequency Resolution
(kHz)
Sample Time (us)
Integration Time (s) Style Survey Region
AO327 327 57/69 56/24 125/82 64 Drift All Arecibo Sky Dec. between -1 & 38
CRAFTS 600 400 ? ? 40? Drift ?
GBNCC 350 100 24 82 120 Pointed All GBT Sky Dec above -40 deg
HTRU-N/S 1352 340 391 64 4200/540/270 Pointed All Sky
LOTAAS 143 32 12 492 3600 Pointed Northern Sky Dec > about 0 deg
PALFA 1375 323 336 65 268/180 Pointed Galactic Plane in Arecibo Dec Range
Arecibo 327 MHz Drift Survey (AO327) - Deneva et al. 2013, ApJ, 775, 51 The Commensal Radio Astronomy FAST Survey (CRAFTS) Green Bank North Celestial Cap (GBNCC) - Stovall et al. 2014, ApJ, 791, 67 High Time Resolution Universe - South (HTRU-S) - Keith et al. 2010, MNRAS, 409, 619 High Time Resolution Universe - North (HTRU-N) - Barr et al. 2013, MNRAS, 435, 2234 LOFAR Tied-Array All-sky Survey (LOTAAS) - Coenen et al. 2014, A&A, 570, 60 Arecibo L-Band Feed Array Pulsar Survey (PALFA) - Cordes et al. 2006, ApJ, 637, 446
Targeted Pulsar SearchesFermi Unassociated Gamma-ray sources
Locations of gamma-ray sources are searched using various radio telescopes.
Drifting Subpulses & Nulling
Mode Changing
Rotating Radio Transients
B1913+16: First Binary Pulsar
Binary Parameters
Keplerian Binary ParametersOrbital Period: PB
Projected Semimajor axis: A1 Time of Periastron Passage: T0
Eccentricity: E Longitude of Periastron: OM
Post-Keplerian Parameters
! = 6ıfb(2ıMfb)23 (1� e2)�1
‚ = e(2ıfb)�1(2ıMfb)23m2M (1 + m2
M )
Pb = � 192ı5 (2ı—fb)
53 F (e)
r = m2
s = sin(i)
Double Pulsar GR TestsPSR J0737-3039A/B
Massive Pulsars & EOSPSR J0348+0432 Pulsar Mass = 2.01 +/- 0.04 Antoniadis et al. 2013, Science, 340, 448
PSR J1614-2230 Pulsar Mass = 1.97 +/- 0.04 Demorest et al. 2010, Nature, 467, 1081