Pulsars and neutron stars/Related objects

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-scale 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

Name	Dispersion measure (cm-3pc)	R.A.	Dec.	UTC	Telescope	Year	Reference
010621	746	18:52	-08:29	13:02:10.795	Parkes	2011	[1]
010724	375	01:18	-75:12	19:50:01.630	Parkes	2007	[2]
010125	790	19:06	-40:37	00:29:13.230	Parkes	2014	[3]
110220	944	22:34	-12:24	01:55:48.957	Parkes	2013	[4]
110627	723	21:03	-44:44	21:33:17.474	Parkes	2013	[5]
110703	1104	23:30	-02:52	18:59:40.591	Parkes	2013	[6]
120127	553	23:15	-18:25	08:11:21.723	Parkes	2013	[7]
121002	1629	18:14	-85:11	13:09:18.402	Parkes	2013	[8]
121102	557	05:32	+33:05	06:35:53.243	Arecibo	2014	[9]
131104	779	06:44	-51:16	18:04:01.200	Parkes	2014	[10]
140514	562	22:34	-12:18	17:14:11.06	Parkes	2014	[11]

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.