Predicting the BRAING INDEX OF INTERMITTENT AND NULLING PULSARS Speaker Abdujappar rusul From CCNU

Content: Introduction to a pulsar and its braking index Intermittent PSR B1931+24 A study of the braking index of intermittent pulsars and nulling pulsar conclusions

Observations revealed that its spin axe and magnetic axe is not aligned in usual。 Observations confirmed that pulsar is a remnant of supernova explosion (Crab pulsar) Pulsar magnetosphere is believed to be surrounded with charged plasma, which is created by the pair cascade near the star surface The observed pulsar radio emission features showed that pulsar is broadband coherent radio emitting source

Emission prosperities Vela pulsar 4min J1646-6831 J1647-36 J1226-32 4 minute time series

Standard model of pulsar magnetosphere According to the observed features, researchers proposed that pulsar emission is magnetic dipole radiation to see whether it is truly magnetic dipole radiation field or not, we always measure a parameter know as braking index

Measuring the braking index In observation, the unresolved glitch in the data and unknown timing noise would not allow a precise measurement of spin frequency second derivatives; this results in unreliable braking index (Hobbs 2010) Because the above reason, observers only measured 7-8 pulsars’ braking index among 2328 (From a talk of Lorimer) pulsars population

Measured Braking Indices

BRAKING INDEXTELLS……… Observed braking indices are all smaller than３ But the magnetic dipole field expected it as 3 This indicates that, in addition to magnetic dipole radiation, another physical process must contribute to the torque acting on pulsars (Livingstone et al. 2007). Scientist believe that there must be additional energy loss by the out flowing charged plasma

Intermittent pulsar

“on”》“off” Intermittent pulsar the difference between the “on” and “off” state rotational slow-down energy loss Where T is torque generated by out flowing plasma current and magnetic field

Theorists have their luck!

The out flowing plasma current – pulsar wind Intermittent pulsar The observations of intermittent pulsar B1931+24 confirmed the existence of out flowing current and provide us the relationship between the pulsar wind torque and magnetic dipole field torque Later observations of intermittent PSR J1841-0500, PSR J1832+0029 and nulling PSR B0823+26 manifest the same feature as PSR B1931+24

significance because we need to know We need further study about “on” and “off” state magnetosphere configuration Intermittent pulsar Like many other pulsars, for the intermittent pulsar, the importance of the measurement of braking index has its significance because we need to know 1. Dose “on” state braking index smaller than 3 2. Dose “off” state braking index equals 3 or not Yet, observers could not measure the braking index of PSR B1931+24 even after 13 yr of observation because of the lack of data about its transition into (or out of) a radio-on phase (Young et al. 2013).

The braking index of intermittent pulsars It looks like, at least, we need a model to study about the braking index

The braking index of intermittent pulsars We need to take time derivative to this equation When we assume and are constant

The braking index of intermittent pulsars We have the variables polar cap radius and charge density With this 2 variables, we discussed 3 different cases 1. Charged density is constant 2. Polar cap radius is constant 3. both of them are variables

The braking index of intermittent pulsars

The braking index of intermittent pulsars For the first case Here, for simplicity, we only discuss the case 1

Observations show different “on”//”off” ratios in different observing epochs

The braking index of intermittent pulsars Observations revealed that the braking index is constant in relatively short observing period, for example 0.5% in 21, ~2% in 40 years for Crab So, we assume that the braking indices in “on” and “off” of neighboring observations are constant,

Results The braking index of intermittent pulsars The calculated braking indices（0.5-3.7）are all almost within the observed domain（0.9-2.8）.

Results Brake index changes with the spin-down ratio

conclusions 1. Under our model, we can predict the braking index of intermittent pulsar with their spin-down ratios 2. Results show that pulsar’s magnetosphere, may never become entirely depleted of plasma during the “off” state and/or we probably missed another energy losing factor in our approach to study the intermittent pulsars.

Thanks 谢谢大家