Timing Analysis of The Geminga Pulsar Huang Hsiu-hui Institute of Physics, NTHU

Outline Motivation Introduction Observations Data reduction Timing analysis Future work Reference

Motivation As proposed by some authors, waves may exist on neutron star surfaces due to the tidal force of their companion stars or the return current from their magnetosphere. These possible waves may propagate on the stellar surface, periodically affect the emission mechanisms and leave some indelible signatures. If these waves can be detected, they will be very helpful to probe the structure of neutron stars.

Introduction First discovered in 1972 by the SAS-2 satellite. It was detected in x-ray by Einstein Observatory in An optical counterpart of the Geminga was found by Bignami et al. (1987). It was found to be a rotation-powered pulsar with a period of 237 ms in x-rays by ROSAT (Halpern & Holt 1992) and in γ-rays by the EGRET on the CGRO (Bertch et al. 1992).

RA: 6h33m54s; Dec: +17 º 46 ’ 12 ” (J2000) PSR J ; 2CG195+14; 1E The parallax distance measured by HST is about /-34 pc (Caraveo et al. 1996) RA. proper motion (mas/yr): 138 Dec. proper motion (mas/yr): 97

Period: ~237ms The period derivative: 1.1x10^-14 The characteristic age: ~3.4x10^5 yr The spin-down power: 3.3x10^34 erg/s The magnetic field: 3-5x10^11G A glitch in γ-rays : MJD~50382 ( )

Observations 1994 & 1999 ASCA GIS data 1996 RXTE PCA data 2002 XMM data

ASCA Lifetime : February 20, March 2, 2001 Four X-ray telescopes (1) Gas Imaging Spectrometer (GIS; keV) (2)Solid-state Imaging Spectrometer (SIS; keV)

1994 ( ) 1. Date: Total exposure time: ~73.6 ksec 3. Time resolution: E-3 sec 1999 ( ) 1. Date: Total exposure time: ~180 ksec 3. Time resolution: E-3 sec

RXTE Livetime : 30 December 1995 to the present Payload : 1. Proportional Counter Array (PCA) energy range: 2-60 keV, time resolution 1 microsec 2. High Energy X-ray Timing Experiment (HEXTE) keV energy range 3. All-Sky Monitor (ASM) 2-10 keV energy range

RXTE PCA data (10213) 1. Date: (22 pointing) 2. Total exposure time: ~118 ksec 3. Time resolution: E-7 s

XMM-Newton The X-ray Multi-Mirror Mission Lifetime : December 1999 to the present Energy Range : keV Payload : 1. European Photon Imaging Camera (MOS & PN) 2. Reflection Grating Spectrometer 3. Optical Monitor

XMM (MOS, PN mode) 1. Date: Total exposure time: ~103 ksec 3. Time resolution: ~ms

Data Reduction ASCA 1. Region: 4 (94) /3 (99)arcmin 2. GTI filter 3. Barycentric correction 4. Select channel: KeV (15~129)

1994, gis2, 4 ‘

3 ‘ 5 ’ 6.25 ‘ ASCA GIS (1999) 3 arcmin 2002 ApJ

1999, gis2, 3 ‘

1994, gis2

1999, gis2

RXTE XMM

Timing analysis The Fourier Transform Epoch folding H-test

The best-fit period is ±0.1μs ROSAT PSPC (1991)

EGRET data

*Comparison of background-subtracted pulse profiles in the 0.5 – 4.0 keV band from 1994 and 1999 ASCA GIS observations of Geminga. *It was determined that the light curves do not differ significantly.

1994

1999

1994

1994, H-test

1999

1999, H-test

Future work Search for signature of waves on the surface of neutron stars. How?? * Our strategies: 1. Eliminate (time resolution, period) 2. Consider the signals with the low random probability 3. Confirm (from another data: RXTE & XMM) 4. Neutron star oscillation ( )

Reference Discovery of soft x-ray pulsations from the γ- ray source Geminga. (1992 Nature) A BROADBAND X-RAY STUDY OF THE GEMINGA PULSAR. (1997 ApJ) A HIGH-ENERGY STUDY OF THE GEMINGA PULSAR. (2002 ApJ) HST/FOC observations confirm the presence of a spectral feature in the optical spectrum of Geminga. (1998 A&A)