Gamma-ray Observations of Pulsars in the Fermi Era Paul S. Ray - PowerPoint PPT Presentation

Gamma-ray Observations of Pulsars in the Fermi Era Paul S. Ray (NRL) for the Fermi LAT Collaboration, Fermi Pulsar Timing Consortium and Fermi Pulsar Search Consortium Pablo Saz Parkinson Santa Cruz Institute for Particle Physics (SCIPP), UCSC 2013 July 8 FAN4 - University of Hong Kong Thursday, July 11, 13

Fermi Gamma-ray Space Telescope Large AreaTelescope (LAT) 20 MeV - >300 GeV Gamma-ray Burst Monitor (GBM) NaI and BGO Detectors 8 keV - 40 MeV Key LAT Features for Pulsars Large area: 8000 cm 2 area (at 1 GeV) Broad band: 20 MeV to >300 GeV Good localization: 0.6–0.8 deg radius PSF (1 GeV) Continuous sky survey mode of operation with wide FOV (Atwood et al. 2009, ApJ, 697, 1071) Thursday, July 11, 13

Fermi in Space Launch from Cape Canaveral 11 June 2008. Circular orbit, 565 km altitude (96 min period), 25.6 deg inclination. Soon to complete 5 years of survey observations, with a planned mission of 10 years. Usual mode of operation is scanning, so that the entire sky is viewed every two orbits. Thursday, July 11, 13

LAT Gamma-ray Candidate Event LAT is a pair conversion telescope For each event, the ground-based reconstruction algorithms measures three quantities: arrival direction, energy, and arrival time. Thursday, July 11, 13

Four years of LAT survey data 5 Thursday, July 11, 13

Three+ Ways to Detect Pulsars with the LAT • Folding gamma-ray photons according to a known pulsar timing model, from radio or X-rays All 6 EGRET pulsars were detected this way (but Geminga, Crab and Vela could have been discovered in blind searches; Ziegler 2008, Chandler et al. 2001) • Blind searches for pulsations directly in the gamma-ray data Spectacularly successful for young pulsars Really hard for MSPs! • Radio pulsar searches of LAT unidentified sources Sensitivity to MSPs, binaries, very noisy pulsars + New : Optical studies of LAT source locations to find binary pulsar counterparts Still need a blind frequency search to detect pulsations Thursday, July 11, 13

Folding With Ephemerides Large campaign to provide radio and X-ray timing models for all (~200) pulsars with Ė > 1 x 10 34 erg/s (Smith et al. 2008 A&A, 492, 923) Thanks to all members of the Pulsar Timing Consortium! Folded LAT photons for 762 pulsars About 40 new γ -ray pulsars discovered in this way Thursday, July 11, 13

Bright gamma-ray pulsars with Fermi High signal-to-noise and good timing models allow study of fine features in the light curve and evolution of profile shapes with energy Phase-resolved spectroscopy reveals rapid changes is spectral parameters (e.g. cutoff Preliminary energy) within gamma-ray peaks Many pulsars have sub-exponential phase- averaged spectra from superposition of range of exponential cutoffs. Phase resolved spectroscopy is important for proper modeling. (DeCesar et al. 2012) Thursday, July 11, 13

from 1 to 8 MSP γ -ray profiles Kuiper et al. 2000, A&A, 359, 615 Most MSP profiles (peak separation & radio lags) look very much like the young (Abdo et al. 2009, Science, 325, 848) pulsars Thursday, July 11, 13

from 8 to many γ -ray MSPs Kuiper et al. 2000, A&A, 359, 615 Fig. 1. MLR map for energies MeV of a sky region centered Thursday, July 11, 13

where to search for more ? in globular clusters toward LAT unidentified sources: radio/blind searches toward “pulsar-like” LAT sources toward potential X-ray/opt counterparts Thursday, July 11, 13

γ -ray MSPs in Globular Clusters in M28: B1821-24 + N MSP ∼ 50 in NGC6624: J1823–3021A + N MSP < 32 160 160 see also Wu et al. arXiV:1302.0610v1 > 0.1 GeV J1823-3021A 140 140 120 120 100 100 Counts Counts 80 80 60 60 40 40 20 20 40 > 1.0 GeV 35 > 3.0 GeV Freire+ 2010 Science, 334, 1107 30 Counts 25 20 highest L γ ∼ 8.4 10 34 erg/s 15 high L γ ∼ 3 10 34 erg/s 10 5 120 0.1 - 1.0 GeV 100 Counts 80 at 8.4 kpc at 5.5 kpc 60 40 20 Radio Flux (au) 1 1.4 GHz 0.8 0.6 0.4 0.2 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Pulsar Phase Thursday, July 11, 13

radio searches in γ -ray Globular Clusters in NGC6652: J1839–3259 LAT glob. clusters with no known radio MSP Long S-band GBT observations, using coherent dedispersion mode of GUPPI DM 63.35 pc cm–3, much less than expected from NE2001 highly (e ∼ 0.95) eccentric 9.25 day orbit, confirming association (rare eccentric binaries in the field) Thursday, July 11, 13

Using LAT to Find Radio Pulsars 575 unassociated 2FGL sources 2FGL Catalog (Nolan et al. 2012) pulsar likeness low variability expo-cut-off spectra multiple techniques for ranking sources Ackermann et al., ApJ 753, 83 (2012) Lee et al., MNRAS 424, 2832 (2012) + patience ! ∼ a year to get orbit, position, Pdot, longer to evaluate pulsar timing array potential and get proper motions (Shlovskii effect) Thursday, July 11, 13

Success! >48 MSPs found! Ray+‘arXiv 1205.3089 Nançay (France) GMRT (India) GreenBank (USA) Parkes (Asutralia) Effelsberg (Germany) Thursday, July 11, 13

blind searches Einstein@Home “guided” searches toward LAT sources 300,000 people have contributed X-ray, optical counterparts perfect for LAT MSP searches (tiny binary orbital parameters flux > data volumes, repetitive computing only sensitive to isolated MSP (1/4 of the total population) currently searching 100 best LAT candidates up to 1200 Hz Romani+ 2012 ApJL 754, 25 Thursday, July 11, 13

X-ray + Optical Studies of bright UNIDs J2339–0533 2 Romani deep X-ray, optical and radio imaging observations to look for likely counterparts Romani et al. 2011, ApJL, 743, 26 only a handful remain to explore Orbital periods identified in optical J2339–0533 : P orb = 4.6 hours J1311–3430 : P orb = 1.56 hours F IG . 1.— HET/SSO/WIYN measurements of J2339 0533. Upper panel: Thursday, July 11, 13

Blind Search MSP Discovery! PSR J1311-3430 Optical: orbital P orb and T asc > 0.1 GeV Search space (free trials): pulsation F 0 (10 8 ), F 1 (10 2 ), X, and orbit 250 P orb and T asc : (10 7 ) 200 Weighted counts 150 extreme black widow Pletsch et al. 2012 100 50 < 0.3 GeV W. counts 80 60 40 20 0.3 − 1 GeV W. counts 90 60 30 1 − 3 GeV W. counts 70 50 30 10 P orb = 1.56 hr 3 − 7 GeV W. counts 12 9 M comp > 8 M Jupiter 6 3 5 > 7 GeV W. c. 3 1 0 0.5 1 1.5 2 Pulse phase Thursday, July 11, 13

But Not Radio Quiet... Ray et al. (2013) Thursday, July 11, 13

Breaking News: J2339–0533! 2.88 ms pulsations discovered in 1.6hr GBT observation at 820 MHz DM 8.72 gives D = 450 pc Measured semimajor axis 0.611 lt-s, larger than expected M C > 0.26 M ⊙◉☊ Redback, not black widow Often not visible LAT pulsations now detected (Ray et al. 2013, in prep) Thursday, July 11, 13

Black Widows & Redbacks Characterize the `weather’ in the system Eclipse mechanism? Understand evolutionary paths Connection to isolated millisecond pulsars? Thursday, July 11, 13

Black Widows & Redbacks Characterize the `weather’ in the system Eclipse mechanism? Understand evolutionary paths Connection to isolated millisecond pulsars? ablated transition companions LMXB → MSP Thursday, July 11, 13

Selecting for Energetic MSPs? Many of these are isolated Thursday, July 11, 13

Second LAT Pulsar Catalog (2PC) (ApJS, accepted: arXiv: 1305.4385) 117 pulsars in 3-yr data light curve, spectra, distances, off-pulse flux, X-ray data, 117 pulsars in 2PC Schlovskii corrections, etc… PRELIMINARY available online 2PC, LAT collaboration, in preparation Thursday, July 11, 13

Second LAT Pulsar Catalog (2PC) (ApJS, accepted: arXiv: 1305.4385) 117 pulsars in 3-yr data light curve, spectra, distances, off-pulse flux, X-ray data, 117 pulsars in 2PC Schlovskii corrections, etc… PRELIMINARY available online 1/3 young + radio-loud 1/3 young + radio-quiet 2PC, LAT collaboration, in preparation 1/3 MSPs Thursday, July 11, 13

▲ Second LAT Pulsar Catalog (2PC) (ApJS, accepted: arXiv: 1305.4385) 117 pulsars in 3-yr data light curve, spectra, distances, off-pulse flux, X-ray data, 117 pulsars in 2PC Schlovskii corrections, etc… PRELIMINARY available online 1/3 young + radio-loud 1/3 young + radio-quiet MSP in globular 2PC, LAT collaboration, in preparation cluster double pulsar 1/3 MSPs Thursday, July 11, 13

radio silent, quiet, faint … loud γ -ray pulsars Thursday, July 11, 13

evolutionary trends in 2PC PRELIMINARY +Xray the older, the more efficient, the 2PC, LAT Colllaboration‘2013, in prep harder 2PC, LAT Colllaboration‘2013, PRELIMINARY in preparation Thursday, July 11, 13

radiation pattern trends in 2PC 2PC, LAT Colllaboration‘2013, in preparation suggestive of one pole seen in γ rays opposite pole in radio no marked evolution of peak separation Δ with Ė Thursday, July 11, 13