Pulsars and Timing. Lucas Guillemot, Ismaël Cognard.!! Rencontre CTA, Observatoire de Paris, 28/11/13

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1 Pulsars and Timing Lucas Guillemot, Ismaël Cognard Rencontre CTA, Observatoire de Paris, 28/11/13

2 Pulsars radio emission cone γ-ray emission fan beam Pulsars are rapidly rotating highly magnetized neutron stars, born in supernova explosions of massive stars. Masses: M, Radii ~ km. Dense plasma co-rotating with the star. Magnetosphere extending to the light cylinder, where Ω x RLC = c. Emission (radio, optical, X-ray, gamma rays ) produced in beams around the star. Pulsars are cosmic lighthouses 2

3 132 GeV γ-ray pulsars (< before Fermi) 42 young radio- and X-ray-selected (green circles, cyan crosses) 36 young γ-ray-selected (white squares) 50 radio-selected MSPs (red diamonds) + 1 γ-ray-selected MSP (yellow diamond) (~15 more to be published)

4 Which pulsars are seen in GeV γ rays? From the Second Fermi LAT Catalog of Gamma-ray Pulsars (2PC), ApJ Suppl. 208, 17 (2013) Ė = I =4 2 I P P 3 Crab pulsar ulsar L. spindown Guillemot, rate, 28/11/13 P, vs. therotationperiodp. Green dots indicate the 42 young, radio-loud gamma-ray pulsars and blue squares show 4 the pulsars, defined as S < 30 µjy, where S is the radio flux density at 1400 MHz. Red triangles are the 40 millisecond gamma-ray pu

5 > (and even >25) GeV pulsars The Astrophysical Journal Supplement Series, 209:34 (34pp), 2013 December From the First Fermi LAT Catalog of Sources above GeV (1FHL), ApJ Suppl. 209, 34 (2013) Among the 514 sources seen by Fermi LAT in 3 years above GeV, 27 are associated with pulsars. Of these 27, 20 (12) have significant > (>25) GeV pulsations 5

6 Pulsed VHE emission from the Crab pulsar Extrapolations above GeV of Fermi LAT spectral results notoriously unreliable How many pulsars can be seen at VHE energies? At least one Pulsed emission from the Crab detected by MAGIC above 25 GeV (Aliu et al. 2008) and by VERITAS above 0 GeV (Aliu et al. 2011). How unique is the Crab? What phenomenon causes the VHE emission? (Other mechanism(s) at work) What fraction of the energy budget? More detections needed Counts per Bin Counts per Bin s -1 ) -2 df/de (MeV cm 2 E χ VERITAS > 120 GeV Fermi > 0 MeV 1500 Phase Phase Crab light curve and spectrum, from Aliu et al., Science (2011) VERITAS, this work Fermi (Abdo et al, 20) MAGIC (Aliu et al. 2008) MAGIC (Albert et al. 2008) CELESTE (De Naurois et al. 2002) STACEE (Oser et al. 2001) HEGRA (Aharonian et al. 2004) Whipple (Lessard et al. 2000) Broken power law fit Exponential cutoff fit 3 Power law with exponential cutoff Broken power law Energy (MeV) Energy (MeV)

7 Constraining Lorentz invariance (LIV) with pulsars cf. e.g. Otte, Proc. ICRC 2011; McCann, Proc. 4 th Fermi Symposium 2012 Does speed of light depend on the photon energy? Linear term: t = dist (E 2 E 1 ) Crab pulsar: peaks seen by Fermi LAT and VERITAS appear to align in phase. ce QG If intrinsic to the pulsar: can be used to constrain LIV. Advantages of LIV experiments using pulsars: limit keeps improving with exposure; does not rely on a transient event; a putative time delay would introduce a phase shift as the pulsar spins down, etc. VERITAS > 120 GeV 1 ms Fermi > 0 MeV 7

8 The pulsar detection problem High-energy data: typically sparse, many pulsar rotations blind search difficult. Earth and satellite motion around the SSB: α, δ Pulsar rotation and spin-down: f 0, f 1, Goal: phase-fold the data with a timing model accounting for every single pulsar rotation over a given interval. Parameters: - right ascension α and declination δ, for converting the photon times to the Solar System Barycenter (SSB). - rotational frequency and time derivatives: f 0, f 1,... - orbital parameters for pulsars in binary systems. Such timing models are easier obtained from radio timing observations, e.g. with the Nançay radio telescope. Binary motion? P b, a, e, T 0, PSR J (P = ms) as seen with Fermi LAT. Left: valid timing model, right: wrong timing model. 8

9 The Nançay Radio Telescope ~94-m equivalent meridian telescope, located in Sologne, 180 km South of Paris. Minimum declination: -39 Pulsar observations at 1.4 and 2 GHz, with 512 MHz bandwidth. Realtime coherent dedispersion of the data. Uncertainty on individual times of arrival of pulsations at the telescope: ~30 ns for some pulsars such as J Pulsar observations represent ~50% of the total telescope time (precision timing for GW searches, timing in support of Fermi, pulsar searches, double pulsar, etc.). 9

10 A key contribution to the success of high-energy pulsar studies Nançay: vital contribution to the success of Fermi LAT pulsar studies > 20 LAT publications used Nançay data. Many pulsars in 2PC (>50% of MSPs) had ephemerides based on Nançay timing measurements. 3 MSPs found in LAT unassociated sources. Also X-rays: RXTE, XMM (e.g. Pancrazi et al. 2012). Nançay could support CTA studies of pulsars by conducting contemporaneous timing observations. How many targets? Observation strategy? Radio, X-ray, and gamma-ray observations of B A (Johnson et al. ApJ 778, 6, 2013) Figure 2. Timing residuals as a function of time for the model given in Table 1 (upper panel), and after whitening of the residuals using eight harmonically related sinusoids (lower panel). The arrow (red in the online version) indicates X-ray ground The tered ephem ing an 1998; incorp each e Event in Sec Pas calibra portan scribe tal and ( 1% Thi in sev

11 CTA will open a new window on the study of pulsars at the highest energies. Nançay can help by supplying contemporaneous timing. Please send questions / comments to: lucas.guillemot at cnrs-orleans.fr icognard at cnrs-orleans.fr