pulsars are cool. seriously. - national radio astronomy...
TRANSCRIPT
![Page 1: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/1.jpg)
Pulsars are Cool. Seriously.
Scott RansomNational Radio Astronomy Observatory /
University of Virginia
![Page 2: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/2.jpg)
Surface temp ~106 K
Magnetic field (Gauss): Millisecond: 108-109
“Normal”: 1011-1013
Magnetar: 1014-1015
Detailed emission mechanisms unknown
Spin rates up to 716 Hz
“Luminosity” up to 10,000x the Sun's!
Surface gravity ~1011 times Earth's
Central densitiesseveral times nuclear
Neutron Stars1.2 - 2 Solar masses
10 - 12 km radii
![Page 3: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/3.jpg)
Surface temp ~106 K
Magnetic field (Gauss): Millisecond: 108-109
“Normal”: 1011-1013
Magnetar: 1014-1015
Detailed emission mechanisms unknown
Spin rates up to 716 Hz
“Luminosity” up to 10,000x the Sun's!
Surface gravity ~1011 times Earth's
Central densitiesseveral times nuclear
Neutron Stars1.2 - 2 Solar masses
10 - 12 km radii
These are exotic objects
![Page 4: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/4.jpg)
TheDiscoveryof Pulsars
PhD student Jocelyn Bell andProf. Antony Hewish
Initially “Little Green Men”Hewish won Nobel Prize in 1974
![Page 5: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/5.jpg)
What are their radio properties?
• Continuum sources
• Typically somewhat to highly linearly polarized
• Steep radio spectra (index of -1 to -3, typical obs freqs 0.3-3 GHz)
• Point sources
• Special ISM effects (freq dependent)
• Highly time variable
• Wide variety of timescales
• Very faint average flux density ~mJy
![Page 6: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/6.jpg)
Confusion?
Timing solns for33 Ter5 MSPs (VLA contours
in green)
None for pulsars!Pulsars separated via time (or spin frequency!) rather
than spatially.
Large beam?Doesn't matter!
Sub-arcsec positions come from pulsar timing.
Gain variations?Who cares?!
Observations are continually“on” and “off” source.
![Page 7: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/7.jpg)
Fundamental Physics with Pulsars
Also many others:
• Plasma physics (e.g. magnetospheres, pulsar eclipses)
• Astrophysics (e.g. stellar masses and evolution)
• Fluid dynamics (e.g. supernovae collapse)
• Magnetohydrodynamics (e.g. pulsar winds)
• Relativistic electrodynamics (e.g. pulsar magnetospheres)
• Atomic physics (e.g. NS atmospheres)
• Solid state physics (e.g. NS crust properties)
Gravitational wave detection (e.g. high precision timing)
Physics at nuclear density (e.g. neutron star interiors)
Strong-field gravity tests (e.g. binary pulsar dynamics)
![Page 8: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/8.jpg)
Basic Physical Information from Pulsars• Rotating dipole magnet in a vacuum (I = 1045 g cm2):
• radiates energy and therefore spins-down (p-dot)
• Surface magnetic field strength (B)
• Spin-down luminosity (E-dot)
• Age (T) and Characteristic Age (c) (braking index: n ~ 3)
![Page 9: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/9.jpg)
P-Pdot DiagramPulsar Hertzsprung- Russell Diagram
HR Diagram:Temp (color) vs Luminosity
P-Pdot DiagramPeriod vs Spindown rate
![Page 10: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/10.jpg)
Pulsar Flavors
Young
Old
High B
Low B
Young(high B, fast spin, very energetic)
![Page 11: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/11.jpg)
CrabNebulaSN1054AD
Pulsar rotates30 times
per second!
Anasazi Indian cave pictogram,Chaco Canyon, NM
![Page 12: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/12.jpg)
The Crab is visible at all energies!
Red = RadioGreen = OpticalBlue = X-ray
![Page 13: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/13.jpg)
Pulsar Flavors
Young
Old
High B
Low B
Young(high B, fast spin, very energetic)
Pulsars move down and right across the diagram as they lose energy (assuming that the magnetic field doesn't change...)
![Page 14: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/14.jpg)
Pulsar Flavors
Normal(average B, slow spin)
Young
Old
High B
Low B
Young(high B, fast spin, very energetic)
![Page 15: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/15.jpg)
Science with “normal” pulsars
Used to:– study the unknown
pulsar emission mechanism
– probe the interstellar medium (scattering, scintillation, rotation measures, electron distribution)
– Measure PSR distances (HI absorption)
Drifting Sub-pulsesBhattacharyya et al 2007
ScintillationWalker et al 2008
![Page 16: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/16.jpg)
Pulsar Flavors
Normal(average B, slow spin)
Young
Old
High B
Low B
Young(high B, fast spin, very energetic)
Eventually they slow down so much that there is not enough spin to generate the electric fields which produce emission.
Their lifetimes are 10-100 Myrs.
![Page 17: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/17.jpg)
Pulsar Flavors
Normal(average B, slow spin)
Millisecond(low B, very fast, very old, very stable spin, best for basic physics tests)
Young
Old
High B
Low B
Young(high B, fast spin, very energetic)
![Page 18: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/18.jpg)
1982:
Enigmatic bright, steep-spectrum, polarized, and scintillating radio source... Using Arecibo:
1.558ms pulsar (640 Hz)!
Courtesy Bob Rood
21x faster than Crab!~half an octave above “Concert A”!
(6 pulses)
![Page 19: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/19.jpg)
Millisecond Pulsars: via “Recycling”
Supernova produces a neutron star
Red Giant transfersmatter to neutron star
Millisecond Pulsaremerges with a white
dwarf companion
Picture credits: Bill Saxton, NRAO/AUI/NSF
Alpar et al 1982Radhakrishnan & Srinivasan 1984
![Page 20: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/20.jpg)
Pulsar Flavors
Normal(average B, slow spin)
Millisecond(low B, very fast, very old, very stable spin, best for basic physics tests)
Young
Old
High B
Low B
Young(high B, fast spin, very energetic)
Recyc
ling!
![Page 21: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/21.jpg)
The Primary Pulsar TelescopesArecibo
Jodrell BankParkes
GBT
![Page 22: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/22.jpg)
New All-Sky Pulsar Surveys● All major radio telescopes are
conducting all-sky pulsar surveys● We know of only about 5% of the
total pulsars in the Galaxy!● Generate lots of data (~50MB/s!):
– 1000s of hrs, 1000s of channels, 15000 kHz sampling: gives more than a Petabyte!
● Requires huge amounts of high performance computing
– Processing 2 min of GBT data requires 2 days on a fast CPU!
– Millions of false positives
Green BankTelescope
![Page 23: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/23.jpg)
DispersionLower frequency radio waves are delayed with respect to higher frequency radio waves by the ionized interstellar medium
t DM-2 (DM = Dispersion Measure)
Coherent Dedispersion
exactly removes this effect, but
is verycomputationally
difficult
High Freq
Low Freq
![Page 24: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/24.jpg)
Scattering and Pulse Broadening
Multipath propagation causes frequency dependent pulse broadening.
-4.4
![Page 25: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/25.jpg)
Searching for New Pulsars• Pulsars are:
• Very weak radio sources
• Binary pulsars show Doppler effects
• Often distant (therefore weaker and high DM)
• Predominantly found in the Galactic Plane (ISM effects)
• Solutions:• Use large telescopes and sensitive receivers
• Use longer integration times
• Use advanced algorithms to adaptively remove interference
• Use advanced algorithms to optimize sensitivity to weak binary MSPs (the hardest PSRs to detect)
Sensitivity (A /Ttot) (tint BW)1/2 Computations Fspin
3 tint
2
![Page 26: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/26.jpg)
Basic Radio Pulsar Search Recipe
Step (% of CPU Time)1. Interference identification and removal (1%)2. De-dispersion of the raw data (5%)3. Normal FFT search (slow pulsars) (15%)4. Acceleration search (binary MSPs) (60%)5. Single-pulse search (15%)6. Sifting of candidates (<1%)7. Folding of candidates (3%)
Processing a single ~2-min “pointing” takes ~2 days!
Big surveys have ~105 pointings, therefore 5+ CPU centuries!
![Page 27: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/27.jpg)
Ter5 A(4th harm)
Ter5 N(3rd harm)
![Page 28: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/28.jpg)
Single Pulse Searches• Some pulsars have highly variable pulse amplitudes or
shut off completely (i.e. nulling) RRATs• Look for dispersed individual pulses (e.g. McLaughlin &
Cordes, 2003, ApJ, 596, 982)
New PALFA Pulsar J1904+07
![Page 29: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/29.jpg)
Year
Numbers have:quadrupled in last 10 yrsdoubled in last ~3 years
Why?Rise in computing capability, sensitive new radio surveys, Fermi!
New Millisecond Pulsars
![Page 30: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/30.jpg)
Currently ~70 new Radio/gamma-ray MSPs because of Fermi!
Courtesy: Paul Ray
~10% of them look like they will be “good timers”
![Page 31: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/31.jpg)
Millisecond Pulsars are Very Precise Clocks
PSR J1737+0747At 12:40PM PST February 17 2015:
P = 4.570136528819804 ms+/- 0.000000000000001 ms
The last digit changes by 1 every 2 minutes!
This extreme precision is what allows us touse pulsars as tools to do unique physics!
This digit changes by 1 every ~4000 years!
![Page 32: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/32.jpg)
Observation 1
Pulses
Time
Obs 2
Pulsar Timing:Unambiguously account for every rotation of a pulsar over years
Obs 3Model(prediction)
Pulse Measurements(TOAs: Times of Arrival)
Predict each pulse to ~200 ns over 2 yrs!
Measurement - Model = Timing Residuals
Time in days
Single day at telescope
![Page 33: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/33.jpg)
Does it work?
PSR J1231-1411~3yrs of Fermi gamma-ray data
~3000 photons (~3/day)
~560 binary orbits
~24 billion rotations of MSP
Perfectly lined up from radio pulsar timing
2 Pulse Rotations
![Page 34: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/34.jpg)
![Page 35: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/35.jpg)
Demorest et al. 2010, Nature
![Page 36: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/36.jpg)
...get a spectacular answer!
The measured difference between the semi-major and semi-minor axes is:
2.8 +/- 0.2 mm!
Ask the right question...
Highly circular orbit has a radius of ~3.4 million km(~5 x Solar radius or ~9 x Earth-Moon distance)
Demorest et al. 2010, Nature
![Page 37: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/37.jpg)
The Binary Pulsar: B1913+16 First binary pulsar discovered at Arecibo Observatory by
Hulse and Taylor in 1974
NS-NS BinaryPpsr = 59.03 ms
Porb = 7.752 hrs
a sin(i)/c = 2.342 lt-s
e = 0.6171
ω = 4.2 deg/yr
Mc = 1.3874(7) M⊙
Mp = 1.4411(7) M⊙
![Page 38: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/38.jpg)
Besides the normal 5 “Keplerian” parameters (Porb, e, asin(i)/c, T0, ω), General Relativity gives:
where: T⊙ GM⊙/c3 = 4.925490947 μs, M = m1 + m2, and s sin(i)
Post-Keplerian Orbital Parameters
(Orbital Precession)
(Grav redshift + time dilation)
(Shapiro delay: “range” and “shape”)
These are only functions of:- the (precisely!) known Keplerian orbital parameters P
b, e, asin(i)
- the mass of the pulsar m1 and the mass of the companion m
2
![Page 39: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/39.jpg)
Besides the normal 5 “Keplerian” parameters (Porb, e, asin(i)/c, T0, ω), General Relativity gives:
where: T⊙ GM⊙/c3 = 4.925490947 μs, M = m1 + m2, and s sin(i)
Post-Keplerian Orbital Parameters
(Orbital Precession)
(Grav redshift + time dilation)
(Shapiro delay: “range” and “shape”)
These are only functions of:- the (precisely!) known Keplerian orbital parameters P
b, e, asin(i)
- the mass of the pulsar m1 and the mass of the companion m
2
Need eccentric orbit andtime for precession
Need compact orbit and a lot of patience
Need high precision,Inclination, and m
2
![Page 40: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/40.jpg)
The Binary Pulsar: B1913+16Three Relativistic Observables: ω, γ, Porb
From Weisberg &Taylor, 2003
Indirect detection of Gravitational Radiation
In 1993, Russell Hulse and Joseph Taylor were awarded the Nobel Prize for their workon PSR B1913+16!
![Page 41: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/41.jpg)
The Double Pulsar: J0737-3039 Faster spin, more compact orbit,
edge on system, 6 relativistic observables, 2 pulsars!
Overall, much better than Hulse-Taylor binary PSR.
Currently GR tests to ~0.01%!
Measured vsPredicted Relativistic
Shapiro Delay
Kramer et al., 2006, Science, 314, 97
![Page 42: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/42.jpg)
Shapiro Delay
NRAO / Bill Saxton
Irwin Shapiro 1964Shapiro et al. 1968, 1971
![Page 43: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/43.jpg)
J1614-2230: Incredible Shapiro Delay Signal
Demorest et al. 2010, Nature, 467, 1081D see Ozel et al. 2010, ApJL, 724, 1990
Mwd = 0.500(6) M⊙
Mpsr = 1.97(4) M⊙!Inclination = 89.17(2) deg!
Full Shapiro Signal
No General Relativity
Full Relativistic Solution
![Page 44: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/44.jpg)
An MSP in a Triple Stellar SystemRecently with GBT:a stellar triple system!
![Page 45: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/45.jpg)
![Page 46: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/46.jpg)
Direct Gravitational Wave Detection (Pulsar Timing Array)● Looking for nHz freq gravitational waves from super massive black hole binaries
● Need good MSPs:● Significance scales with
the number of MSPs being timed
● Must time 20+ pulsars for 10+ years at precision of ~100 nanosec!
For more information, see nanograv.org
Australia Europe North America
Bill Saxton (NRAO/AUI)
![Page 47: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/47.jpg)
Where do these GWs come from?
Coalescing Super-Massive Black Holes• Basically all galaxies have them• Masses of 106 – 109 Solar Masses• Galaxy mergers lead to black hole mergers• When BHs within 1pc, GWs are main energy loss• For “nearby” very massive binaries, we can get
10s of nano-second timing residuals
Potentially measurable with a single MSP, but much better using an array of MSPs.
![Page 48: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/48.jpg)
What about the future?• We only know of about 2,000 out of ~50,000+
pulsars in the Galaxy!
• Many of them will be “Holy Grails”• Sub-MSP, PSR-Black Hole systems, MSP-MSP binary
• Several new huge telescopes...
We need them because we are sensitivity limited!
FAST (500m, China))MeerKAT (64 dishes, SA)
![Page 49: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/49.jpg)
![Page 50: Pulsars are Cool. Seriously. - National Radio Astronomy ...jbraatz/pulsar_summer_lecture_2016.pdf · edge on system, 6 relativistic ... from super massive ... FAST (500m, China))](https://reader033.vdocuments.us/reader033/viewer/2022051723/5ab1a91c7f8b9a7e1d8cbfa7/html5/thumbnails/50.jpg)
Summary
Pulsars are Cool. Seriously.