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We have a star having 1.8 solar mass. Justify any four means (measurable/ observed properties) by which you can identify that the object is a Pulsar and not a white dwarf or a Black Hole.

So one obvious property would be the mass. Since mass > 1.4 solar mass, we can say it is not a white dwarf.

Also the mass is less than 3 solar mass, hence its not a black hole (I'm speaking loosely over here).

Also from periodic radiation patterns, we can say that the object might be a pulsar.

I need help with 2 other means to categorize this object.

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    $\begingroup$ Being a homework question is neither bad nor good, we could recommend how the question could be improved though. Also see Make no prior research or effort a reason to close? $\endgroup$ – uhoh Apr 29 at 2:05
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    $\begingroup$ Please note that many students are being asked to do "at home", uninvigilated exams right now. Please do not answer such questions. $\endgroup$ – Rob Jeffries Apr 29 at 7:44
  • $\begingroup$ This is not an exam, just some assignment, and I am not a school going kid. $\endgroup$ – sanchit krishna Apr 29 at 7:46
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  1. As you said, the mass range of the object indicates that it could be a neutron star, rather than a black hole.

  2. But also the density of the object is a clue. The density of a neutron star is much higher than that of a stable white dwarf.

  3. Extremely regular electromagnetic pulses have to be observed. Known pulsars have a pulse period between 1.4 ms and 8.5 seconds.

  4. The wavelength of the pulses is in the radio range.

  5. Pulsars slow down gradually, at a known rate, so you can measure how the pulse period evolves over time, and check that is compatible with the slow-down rate of a pulsar.

Adapted from this page

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