< Pulsars and neutron stars

Introduction

There are many objects that (probably) are not directly related to pulsars and yet are either found in pulsar surveys (such as the Fast Radio Bursts; FRBs) or have some similarities (such as the pulsing brown dwarfs) and, hence, are studied by pulsar astronomers.

Fast radio bursts

The first discovered fast radio burst (FRB)

Fast radio bursts (FRBs) were first discovered by Lorimer et al. (2007). They are very bright (~Jy peak flux densities) short (millisecond-duration) single pulses with dispersion measures that seem to place the source outside of the Galaxy. A recent reprocessing of the initial discovery (stored in the file SMC021_00861) is shown in the Figure. The x-axis is simply time. The y-axis is the observing frequency and the grey-sale represents the intensity of the signal. Note that this data set is recorded with 1-bit sampling and so the signal is either black (above a threshold) or white (below the threshold). The horizontal line around 1500 MHz is an RFI signal. The FRB is the curve that goes from the bottom to the top of the plot. The "white" region after the pulse is caused by the level setting procedure used to ensure that the 1-bit digitiser does not saturate.

Subsequent discoveries have been described in Thornton et al. (2013), Burke-Spolaor & Bannister (2014) and Spitler et al. (2014).

The following table (based initially on this page) lists the currently known FRBs


NameDispersion
measure
(cm-3pc)
R.A.Dec.UTCTelescopeYearReference
01062174618:52-08:2913:02:10.795Parkes2011
01072437501:18-75:1219:50:01.630Parkes2007
01012579019:06-40:3700:29:13.230Parkes2014
11022094422:34-12:2401:55:48.957Parkes2013
11062772321:03-44:4421:33:17.474Parkes2013
110703110423:30-02:5218:59:40.591Parkes2013
12012755323:15-18:2508:11:21.723Parkes2013
121002162918:14-85:1113:09:18.402Parkes2013
12110255705:32+33:0506:35:53.243Arecibo2014
13110477906:44-51:1618:04:01.200Parkes2014
14051456222:34-12:1817:14:11.06Parkes2014


Some models of FRBs originating in our Galaxy do exist (GIVE REFs), but most theoretical work has concentrated on extragalactic sources (GIVE REFS).


The peryton story

Burke-Spolaor et al. (2011) described a source similar in (some) characteristics to an FRB, but seemed to have a terrestrial origin. These were termed perytons. These have since been shown to be caused by a microwave at the Parkes site.

A peryton event that occurred during a PULSE@Parkes observing session

Ultra-cool dwarfs

Some ultra-cool dwarf stars are observed to have strong radio flares that can be periodic. Hallinan et al. (2006) studied TVLM 513-46546 and found persistent, period radio emission with a period of ~2 hours which agrees with the estimates of the rotational period of the dwarf. The radio emission indicates a high brightness temperature and exhibits circular polarization. They conclude that the radiation is likely to be coherent, electron cyclotron maser emission from above the magnetic poles.

Pulsations from main sequence stars

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