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I know this is a simplistic question, but I cannot find a straight answer...

Also, is it possible most or all neutron stars are magnetars and/or pulsars? It's just hard to see all of their properties from our vantage point, etc.?

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  • $\begingroup$ magnetars are only a small special case fraction of neutron stars, but are all magnetars also pulsars, hmmm.... Nice article (and video) here but no explicit sentences saying that. phys.org/news/2016-08-magnetars.html I don't know if a "pulsar" is something that is observed in some way to pulse, or if its any rotating strongly magnetized object likely to pulse, that would be expected to pulse if one were to measure it. $\endgroup$
    – uhoh
    Commented Oct 20, 2020 at 2:08
  • $\begingroup$ According to Wikipedia magnetars are one of the 3 categories of pulsars. It's not easy to detect a neutron star if it's not a pulsar, and if the beam doesn't sweep the Earth. OTOH, I suppose we may be able to see non-beamed radiation if the neutron star has an active accretion disk, or if the beam creates a tell-tale signature in a nearby gas cloud. $\endgroup$
    – PM 2Ring
    Commented Oct 20, 2020 at 7:48
  • $\begingroup$ Also, from en.wikipedia.org/wiki/Neutron_star There are thought to be around one billion neutron stars in the Milky Way [...] However, most are old and cold and radiate very little; most neutron stars that have been detected occur only in certain situations in which they do radiate, such as if they are a pulsar or part of a binary system. Slow-rotating and non-accreting neutron stars are almost undetectable. $\endgroup$
    – PM 2Ring
    Commented Oct 20, 2020 at 7:53

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Magnetars are the most widely-accepted explanations for two observed classes of objects:

Under the magnetar hypothesis, these classes of objects are explained as highly magnetised neutron stars, evolving from a soft gamma repeater (expected lifetime ~10000 years) to an anomalous X-ray pulsar (expected lifetime ~10000 years) as the rotation period lengthens and the magnetic field decays.

The AXPs are pulsars, and at least some SGRs have been identified with pulsars (e.g. Sgr 0526-26 = PSR B0525-26). So under the magnetar hypothesis, magnetars can indeed be pulsars.

It's worth noting that the magnetar hypothesis may not explain (all?) SGRs and AXPs: there does seem to be evidence that some of these objects do not have especially strong magnetic fields compared to pulsars, e.g. SGR 0418+5729 (Rea et al. 2010), and there have been suggestions that some of these objects may actually be white dwarfs (Lobato et al. 2016), perhaps somewhat similar to the white dwarf pulsar in AR Scorpii.

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Magnetars are a type of pulsar and pulsars are a type of neutron star. So all magnetars are neutron stars, but some neutron stars are not pulsars, and some pulsars are not magnetars.

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However, neutron stars that aren't pulsars are very difficult to observe. And even among the pulsars, there are only 12% of them that we can actually see.

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  • $\begingroup$ The ATNF pulsar catalogue contains about 3000 pulsars. If we assume these represent the 10% that can be observed because of a small beam width, then there are more like 30,000 pulsars. But there are expected to be a billion neutron stars in the Galaxy. Maybe my 1 in 10,000 is too big; I'm not sure how complete the ATNF catalogue will be. $\endgroup$
    – ProfRob
    Commented Oct 20, 2020 at 20:38
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    $\begingroup$ A better way is to note that the lifetime of the pulsar phenomenon is about 1-10 million years. Even if pulsars are born at a constant rate then there would be 1000-10,000 times as many "dead" pulsars. $\endgroup$
    – ProfRob
    Commented Oct 20, 2020 at 20:39
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    $\begingroup$ To add to what Rob said, the beaming fraction isn't the fraction of neutron stars which are pulsars, but the fraction of pulsars which are observable as pulsars to us. $\endgroup$
    – HDE 226868 ♦
    Commented Oct 20, 2020 at 21:30
  • $\begingroup$ "Pulsars are a type of neutron star." This is not strictly true, AR Scorpii shows that occasionally white dwarfs can be pulsars. $\endgroup$
    – user24157
    Commented Oct 22, 2020 at 10:57

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