Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/research/pulsar/orange10/pdf/KranavSharmaOrange2010.pdf Дата изменения: Tue Sep 28 18:09:16 2010 Дата индексирования: Mon Feb 14 00:13:59 2011 Кодировка:

High Precision Timing of 20 Millisecond Pulsars
Supervised by Dr Aidan W. Hotan
Presented by Kranav Sharma M.Sc. (2nd year) Physics Curtin University of Technology


Contents
· Introduction · Component Masses and Orbital Inclinations

· Dispersion Measure Variations and Free Electron Densities
· Proper Motion and Velocities · The Four Different Ages of MSPs


Introduction
· The pipeline processed seven years (2003 ­ 2010.5) observational data was acquired from the ATNF pulsar timing array database. · Data Reduction ­ 20CM CPSR2 only. · Further data reduction ­ removing TOAs with greater uncertainties . · 20 MSPs = 13 binary + 7 solitary


J0437-4715

(17.553)

J1024-0719

(1.298)

PSR J1600-3053

(1.637)

PSR J1713+0747

(7.605)

J1744-1134

(3.081)

PSR J1909-3744

(6.564)


Component Masses and Orbital Inclinations
· Shapiro delay chi-squared fitting in the m2sini plane. · Out of 13 binary, 4 showed appreciable Shapiro delays ­ J0437-4715, J1713+0747, J1857-0943 and J1909-3744 · For the rest, lack of Shapiro delay was used to get estimates on m2 and sini.


Chi-squared contours in m2sini plane

PSR J1713+0747

PSR J1909-3744

PSR J1857+0943


PSR J1022+1001

PSR J1600-3053

PSR J2129-5721

PSR J2145-0750


Dispersion Measure Variations over six years
· We used 20 and 50 cm CPSR2 and PDFBs(only for 50CM) observations · All other parameters kept fixed, we fitted for DM at six months intervals. · The resulting data points were used to provide graphical plots showing DM change with time for all 20 MSPs.


Trends showing DM changes

J1909-3744

J0437-4715

J0613-0200

J1022+1001


J1600-3053

J1643-1224

J1713+0747

J1857+0943


J0711-6830

J1024-0719

J1730-2304

J2124-3358


Free Electron Densities


Proper Motions and Velocities
· We were able to obtain proper motion measurements for all the MSPs and Parallax for 18/20 MSPs. · Using µ and we calculated Distances (d), 2D (transverse) spatial velocities (V), scale heights (z), vertical accelerations (a) and vertical velocities (v)

· Final aim ­ to create Aitoff-Hammer projections for all MSPs


MSP kinematic parameters

Mean of binary transverse velocities = 61±12 km/s rms space v = 74±14 km/s Mean of solitary transverse velocities = 119±30 km/s rms space v = 145±37 km/s


Doppler Effects and Observed P1
(LЖhmer et al. 2004)


Longitude vs. Scale Height


The Four Different Ages Of MSPs
· We employed four different methods to calculate MSP ages, namely Characteristic age, True age, Realistic age and Kinematic age.
(Camilo et al. 1994)

Kinematic Age Tk = d/vz Characteristic Age


Equilibrium Spin Period (Peq)

(Kizitlan and Thorsett 2009)

is the pulsar mass (in terms of 1.4 solar mass) is the accretion rate ( in terms of Eddington rate ) is the radius (in terms of 10 kms) As a reasonable assumption, Peq = Po, can be used to find the true age by using.

(Camilo et al. 1994)


Kizitlan and Thorsett (2010) propose a Realistic Age (substituting Po in the true age equation and n =3) using critical magnetic field as a reference

No mass shedding (Kizitlan and Thorsett 2010) Mass Shedding

Is the critical magnetic field ( for P= 1.08 ms , Bc = 3.67 ± 0.6 X10^8 G Mass shedding period (1.08 ms)


Comparing the four different ages

*Possible Mdot for 1603-7202 for which age < 10 Gyr is <= 0.07Medd. Max possible age is 9661.2 Myr **Possible Mdot for 1824-2452 for which age > 0 is <= 1.9Medd. Min age is 3.0148 Myr ***Possible Mdot for 1939 for which age > 0 is 0.3Medd. Min age is 20.43 Myr


Conclusions
· Most companions are low mass(m <0.4Msun) white dwarfs except for 1022+1001 and J2145-0750 (m>0.5msun). · DM changes should/would affect pulsar timing over long periods of time. We do need continuous multi-frequency data to precisely track DM changes. · We did find some difference in transverse velocities between binary and solitary MSPs (contrary to Hobbs et al. 2005 and Toscano et al. 1999), which was unexpected. · We found that Characteristic age is a reasonable assumption for estimating MSP ages as younger MSPs (J1939+2134 and J1824-2452) have greater P1 that older ones.