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Precise Pulsar Timing and Radio Follow-Up of Pulsars Discovered in LAT Blind Periodicity Searches Paul S. Ray on behalf of the LAT Collaboration and the Fermi Pulsar Search Consortium (PSC) Blind Search Pulsars Before Fermi, Geminga

SLIDE 1

Precise Pulsar Timing and Radio Follow-Up of Pulsars Discovered in LAT Blind Periodicity Searches

Paul S. Ray

n behalf of the LAT Collaboration

and the Fermi Pulsar Search Consortium (PSC)

SLIDE 2

Blind Search Pulsars

Before Fermi, Geminga was the
nly “gamma-ray only” pulsar
16 discovered in first 6 months

(see Abdo et al. 2009, Science, 325, 840)!

8 new discoveries since then!

(see Saz Parkinson and Dormody talks on Wednesday)

Questions:
What is their timing behavior?
These are “gamma-ray

selected” pulsars, but are they also radio quiet?

Are there counterparts at
ther wavelengths?

➡ Need precise positions!

0.5 1 1.5 2

Number of Counts

20 40 60 80 100 120 140

(a) J0007+7303

0.5 1 1.5 2

Number of Counts

5 10 15 20 25 30 35

(b) J0357+32

0.5 1 1.5 2

Number of Counts

10 20 30 40 50 60 70

0.5 1 1.5 2

Number of Counts

20 40 60 80 100 120 140 160

(d) J1418-6058

0.5 1 1.5 2

Number of Counts

10 20 30 40 50 60 70

(e) J1459-60

0.5 1 1.5 2

Number of Counts

20 40 60 80 100 120 140 160 180 200

(f) J1732-31

0.5 1 1.5 2

Number of Counts

10 20 30 40 50 60 70

(g) J1741-2054

0.5 1 1.5 2

Number of Counts

50 100 150 200 250

(h) J1809-2332

0.5 1 1.5 2

Number of Counts

10 20 30 40 50 60 70 80 90

(i) J1813-1246

0.5 1 1.5 2

Number of Counts

50 100 150 200 250 300

(j) J1826-1256

0.5 1 1.5 2

Number of Counts

20 40 60 80 100 120

(k) J1836+5925

0.5 1 1.5 2

Number of Counts

20 40 60 80 100 120 140 160

(l) J1907+06

0.5 1 1.5 2

Number of Counts

10 20 30 40 50 60 70 80 90

(m) J1958+2846

0.5 1 1.5 2

Number of Counts

20 40 60 80 100 120 140 160 180 200

(n) J2021+4026

0.5 1 1.5 2

Number of Counts

20 40 60 80 100 120 140 160 180 200

(o) J2032+4127

0.5 1 1.5 2

Number of Counts

10 20 30 40 50 60

(p) J2238+59

SLIDE 3

LAT Pulsar Timing

Survey mode observing and large FOV

and area make for excellent long term timing of pulsars discovered

Developed Maximum Likelihood

method for measuring TOAs from small numbers of photons (typically ~100 photons per 2-week TOA). Achieves sub-ms residuals on most pulsars

All 24 blind search pulsars timed, plus

several others where the LAT is better than any alternative (Geminga, PSR J1124–5916, Vela)

METHOD

Convert photon times to the

Geocenter

Assign phases using a

preliminary timing model

Construct analytical model
f pulse profile
Divide data set into

segments

Using ML, fit for phase offset

between profile and data in each segment

SLIDE 4

LAT Pulsar Timing

Survey mode observing and large FOV

and area make for excellent long term timing of pulsars discovered

Developed Maximum Likelihood

method for measuring TOAs from small numbers of photons (typically ~100 photons per 2-week TOA). Achieves sub-ms residuals on most pulsars

All 24 blind search pulsars timed, plus

several others where the LAT is better than any alternative (Geminga, PSR J1124–5916, Vela)

SLIDE 5

The Power of Timing

Improved rotational parameters
Study timing noise and glitches (free

from any radio propagation effects)

Glitch detected in CTA1 pulsar on

2009 May 1

Precise positions, which enable

multiwavelength follow up!

Sub-ms residuals lead to arcsec

position accuracy

PSR J1741-2054 PSR J1836+5925 Ray et al. 2009, in preparation

SLIDE 6

LAT Pulsar Search Consortium (Radio)

All these new pulsars are gamma-ray selected (discovered in

blind periodicity searches of LAT data), but are they radio quiet?

Some (CTA1, 3EG J1835+5918) already have stringent radio limits
For the others, we recruited pulsar observers with expertise at key
bservatories (Parkes, Arecibo, GBT, Effelsberg, Nançay)
Radio detection yields
Distance from Dispersion Measure (DM)
Information on emission region from radio to gamma-ray offset
Geometry from polarization studies
Population studies of radio quiet vs. radio loud, which constrain models

SLIDE 7

Fermi PSC

Purpose: To organize deep radio searches of the blind search

pulsars and unidentified LAT sources (see following talk by Ransom)

Fermi LAT members:
Ray, Smith, Harding, Thompson, Saz Parkinson, Ziegler,

Abdo, Wood, Romani, Kramer (Effelsberg), Johnston (Parkes), Theureau, Cognard (Nançay)

External members on MOU:
GBT: Camilo, Ransom, Roberts
Arecibo: Freire
Jodrell Bank: Stappers
Parkes: Keith, Weltevrede

SLIDE 8

PSC Observations

Parkes: 4 of the most southern sources + a dozen UNID

sources

Arecibo: 5 pulsars + 10 UNID sources
GBT: 5 pulsars + 27 UNID sources from the BSL + 50 fainter

UNID sources

Jodrell observes when needed
Effelsberg just started observing with new filterbank
Nançay also contributing

SLIDE 9

First Two Radio Detections

PSR J1741-2054
Radio pulsar found in archival Parkes

multibeam data

Extremely low DM (4.7 pc cm-3),

implies D=400pc

May be lowest luminosity of any young

radio pulsar (L~0.025 mJy kpc2)

PSR J2032+4127
Pulsations discovered at GBT
DM=115 implies D=3.6 kpc, but may be

at half that distance (possibly associated with Cyg OB2)

Camilo, Ray, et al. 2009, ApJ, 705, 1

SLIDE 10

New Detection: J1907+06!

Very faint radio pulsations

(~3.5 µJy) detected at Arecibo!

DM 80 pc cm-3 gives distance of

3.1 kpc

Another very low luminosity

pulsar

See talk by Abdo on Wed.

Abdo et al. 2009, ApJ, submitted

SLIDE 11

Radio Upper Limits

25 gamma-ray selected pulsars

➡ 3 detected, 21 upper limits (all <70 µJy), 1 left to observe

(Pulsars with P>30 ms)

SLIDE 12

What is “Radio Quiet”?

The new radio detections are very low luminosity!

(Pulsars with P>30 ms and Age<107 yr)

SLIDE 13

Summary

The LAT has given us an abundance of gamma-ray selected

pulsars

Pulse timing with the LAT yields arcsec accuracy positions

and the spindown behavior of these pulsars

The PSC has made radio observations of all but one
3 detected in radio, others have deep upper limits
Detections immediately give distance measurement!
When combined with LAT upper limits on gamma-ray

Precise Pulsar Timing and Radio Follow-Up of Pulsars Discovered in LAT Blind Periodicity Searches

Paul S. Ray

and the Fermi Pulsar Search Consortium (PSC)

Blind Search Pulsars

➡ Need precise positions!

LAT Pulsar Timing

LAT Pulsar Timing

The Power of Timing

from any radio propagation effects)

2009 May 1

multiwavelength follow up!

position accuracy

LAT Pulsar Search Consortium (Radio)

blind periodicity searches of LAT data), but are they radio quiet?

Fermi PSC

pulsars and unidentified LAT sources (see following talk by Ransom)

Abdo, Wood, Romani, Kramer (Effelsberg), Johnston (Parkes), Theureau, Cognard (Nançay)

PSC Observations

sources

UNID sources

First Two Radio Detections

multibeam data

implies D=400pc

radio pulsar (L~0.025 mJy kpc2)

at half that distance (possibly associated with Cyg OB2)

New Detection: J1907+06!

Radio Upper Limits

➡ 3 detected, 21 upper limits (all <70 µJy), 1 left to observe

What is “Radio Quiet”?

Summary

pulsars

and the spindown behavior of these pulsars

pulsations from radio pulsars population studies will provide interesting constraints on models