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Fermi Symposium - Washington DC - 11/09/2015
[email protected],H.J.Pletsch,J.Wu,L.Guillemotonbehalfofthe
Fermi-LATCollabora?on
1
Fermi Symposium - Washington DC - 11/09/2015
BlindSearchProblem
Assign rotation phases to photons and calculate Fourier power:
2
�(t) = 2⇡f(t� t0) + ⇡f(t� t0)2 Pn =
1
2
������
NX
j=1
wj e�in�(tj)
������
2
O(1022) trials required per source for a coherent search!
S1 =NX
j,k
wjwk e�i[�(tj)��(tk)] W rect
T (⌧jk) ˆW rectT (⌧) =
(1, |⌧ | T/2
0, otherwise .
Similar to Atwood et al. (2006), only sum coherently up to T, and combine power incoherently:
Search parameter space is 4D:n
f, f ,↵, �o
Fermi Symposium - Washington DC - 11/09/2015
Op?misingaBlindSearch
3
Pletsch, H. J. & Clark C. J., 2014, ApJ 795, 75
−2 −1 0 1 2
0
0.2
0.4
0.6
0.8
1
Frequency/fNy
Matc
hin
S(f
)
Atwood et al. (2006)
Previous E@H
0 0.25 0.5 0.75 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency offset (Fourier bins)
Matc
hin
Sg
Maximise search sensitivity at a fixed computing cost
1. Optimal spacing of grid points throughout parameter space
2. Lag- and frequency-domain interpolation to reduce losses
3. Refinement and follow-up stages
Pulsed fraction0.1 0.15 0.2 0.25 0.30
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
p
PDETatP
FA=
10−3
Atwood et al. (2006)
3. Multistage
2. Semicoh. w/ interp.
1. Semicoh.
45%
Det
ectio
n pr
obab
ility
Fermi Symposium - Washington DC - 11/09/2015
Einstein@Home
4
Previous Hannover discoveries• 11 new gamma-ray pulsars • Another 4 after moving to E@H
http://einsteinathome.org/
GW, Radio & Gamma-ray searches• 54 new radio pulsars
A volunteer supercomputer• Unused computing cycles
from 75,000 active computers • ~2 PFlop/s sustained
computing power
Fermi Symposium - Washington DC - 11/09/2015
SurveySetup
5
104 - 106 work units per source11,991,296 total — O(10,000) CPU years!
10�1 100 101 102 103
f (Hz)
10�18
10�17
10�16
10�15
10�14
10�13
10�12
10�11
10�10
10�9
�f
(Hz/
s)
1 ⇥ 10 33 erg s�1
1 ⇥ 10 36 erg s�1
1 ⇥ 10 39 erg s�1
1⇥ 1015
G
1⇥ 1014
G
1⇥ 1013
G
1⇥ 1012
G
1⇥ 1011
G
1 ⇥ 102 yr
1 ⇥ 104 yr
1 ⇥ 106 yr
1 ⇥ 108 yr
Radio PulsarLAT-discovered PulsarGamma-ray Pulsar
Latest E@H Search:
• 118 unidentified pulsar-like 3FGL sources
• Early Pass 8 data until Apr./Oct. 2014
• Relocalised source positions
See poster from J. Wu for details!
• Using newly-improved search methods
Fermi Symposium - Washington DC - 11/09/2015
3FGLJ1906.6+0720
6
• Most significant remaining unassociated 2FGL source
• Among top 10 unidentified 3FGL sources
• Highest ranking pulsar candidate source in 2FGL
• No pulsations detected in radio or gamma-ray searches
Lee, K. J. et al. 2012, MNRAS, 424, 2832
Xing, Y., & Wang, Z. 2014, PASJ, 66 Barr, E. D. et al. 2013, MNRAS, 429, 1633
Romani, R. W. 2012, ApJ 754, L25
Fermi Symposium - Washington DC - 11/09/2015
PSRJ1906+0722-Complica?ons
7
One of the largest glitches detected from a gamma-ray pulsar
�f/f ⇡ 4.5⇥ 10�6
20s30s40s19h06m50s
Right Ascension (J2000)
160
200
+07�240
Dec
linat
ion
(J20
00)
31s.1531s.255400
5500
5600
5700
+19h06m
+07�220
Large angular offset between pulsar and 3FGL source
Clark, C. J., Pletsch, H. J., Wu, J., et al. 2015, ApJL, 809, L2
Fermi Symposium - Washington DC - 11/09/2015
Off-pulseAnalysis
8
5’
To PSR
Image credit: X-ray: NASA/CXC/Univ of Manitoba/S.Safi-Harb et al, Optical: DSS,
Infrared: NASA/JPL-Caltech
5’
Off-pulse analysis revealed a new source ~0.3 deg away from timing position.
Possible interaction between SNR (3C 397) and molecular cloud?
Fermi Symposium - Washington DC - 11/09/2015
Outlook
• First set of 118 sources almost complete, adding more with the latest Pass 8 data
• Searches for gamma-ray pulsars in binary systems in development
9Thank you for listening!
PSR J1906+0722
Preliminary!
Minimum detectable pulsed fraction
