Explaining the ring-like waves of X-ray emission around the Crab pulsar

X-ray map of the inner portion of the Crab Nebula.

Credit: NASA/CXC/MSFC/M.Weisskopf et al & A.Hobart

Click below to view video

In a recent comment, gmagee inquired about the rings of X-ray emission that are seen to be expanding away from the Crab pulsar and whether this activity might be more likely interpreted as being intrinsic to the pulsar wind rather than to an impacting galactic cosmic ray volley.  This ring motion was reported in the news today, one story appearing in PhysOrg (http://www.physorg.com/news/2011-05-crab-nebula-action-case-dog.html).
In answer to this question, I would respond, no.  The expanding ring of emission is most likely produced by the superwave, not by the Crab pulsar.  Much of the misconception on interpreting this phenomenon concerns the all too common belief that the Crab pulsar lies near the geometrical center of the Crab Nebula.  This misconception is perpetuated not only in technical papers but in media news reports such as the above cited report.  To the contrary, as I had proposed in chapter 5 of my 1983 Ph.D. dissertation (see in particular pp. 179 – 180 of the dissertation update), a careful analysis of the kinematics of the Crab pulsar and of the high velocity filaments traveling outward from the explosion center shows that the Crab pulsar is most likely situated at the forefront of the Nebula (4 – 5 light years from the center) and is traveling almost directly towards us at ~1500 km/s (2° angle deviation from our line of sight).  Only when viewed in projection from our vantage point does it “appear” to lie at the geometrical center of the Nebula.  I would rather not go into the details of this explanation here since it is rather extensive, but refer readers to my dissertation.  Also the peripheral nebular placement of the Crab pulsar is to a much less extent dealt with on page 74 of Decoding the Message of the Pulsars.  Other reasons why the pulsar is not the source of the cosmic rays energizing the Crab Nebula are given in my dissertation, in my 1987 Earth, Moon, and Planets paper, and in chapter 10 of my book Earth Under Fire.

This high velocity scenario I am proposing suggests either that 1) the Crab supernova explosion was asymmetrical in such a manner as to eject its central neutron star outward in our direction, or 2) that the Crab neutron star progenitor was part of a close binary and that its partner star destroyed itself in the explosion and simultaneously ejected and propelled its neutron star partner outward along the pulsar’s current trajectory.  Examples of such hyperfast pulsars are PSR B1508+55 and B1757-24.  An example of B1757-24 is shown in the image below.  If this were the Crab pulsar, we would be far off to the right viewing the pulsar and its nebula face on.

Pulsar B1757-24 in the constellation of Sagittarius

As I pointed out 28 years ago in my dissertation, an impacting superwave would create a bow shock region around the Crab pulsar.  Hence waves of superwave cosmic rays hitting this shock region, travelling way from us into the plane of the sky at the Crab location, would give the appearance to us of concentric rings of X-ray emission expanding away from the Crab pulsar as they proceded in the anticenter direction to the rear of the pulsar.  The shock front generating these moving X-ray rings (in the vicinity of the Nebula’s luminous wisps) may not necessarily correspond with the shock region that I have suggested is responsible for producing the gamma ray synchrotron emission flares.  There may be several such emission nodes in the supernova shell that would be emitting high energy radiation.  But they may not necessarily all be at the same distance relative to a given cosmic ray front in the superwave.  So although the Crab pulsar X-ray rings and the gamma ray flares are both being energized by superwave cosmic rays, they would not necessarily be impacted simultaneously by a given front.  This would explain why no correlative results are seen for the two emission phenomena.

[I would like to point out here that in giving the above explanation I am not constructing a model a posteriori to  fit the data.  My model was proposed 28 years ago and I see no reason to change it.  I am simply explaining how this apriori proposed model would produce the observed results.  In short, findings which astronomers say seem very mysterious, are seen not really to be that mysterious after all.]

Viewing coherent gamma synchrotron emission from the Crab Nebula

In a comment to the previous posting, gmagee has asked why a superwave hitting the entire remnant would  cause us to see a flare, given that the remnant is many light years in size.  He wonders why the emission due to a brief rise in superwave cosmic ray intensity would not average out over the entire remnant, thus preventing us from seeing an intensity change lasting only a few days.

The reason is that we are seeing gamma radiation from a very small area of the Nebula.  We don’t see the majority of the gamma ray emission radiated by the entire Nebula during a gamma ray flare; we only see the gamma emission that is directed precisely in our direction.  In other words, this gamma emission is coherent synchrotron emission, rather than incoherent synchrotron emission.  Consider that the cosmic rays producing this gamma emission are normally considered to have energies of between 1015 to 1016 ev.  This means that the cosmic ray electrons have Lorentz factors (γ) of between 109 and 1010.  Electrons of such high energy beam their gamma synchrotron emission in a narrow cone in the forward direction of their travel where the cone aperture has a half diameter of: θ =  1/γ radians = 10-9 – 10-10 radians.  This equals just 0.2 to 0.02 milliarc seconds!  So when these gamma rays are orbit around magnetic field lines encountered in the Crab’s magnetized plasma sheath, they will beam their radiation in a very limited direction which we will see only when those electrons are aimed towards us in their gyration orbit.  A deviation of more than this angle and their radiation will be entirely invisible to us.  The actual radiation cone that will be beamed out will be wider than this because the superwave cosmic rays impacting the Nebula will have some degree of angular dispersion.  Let us say that the incident volley has an angular variation of 1 degree of arc.  Then cosmic ray electrons spiralling around Nebula field lines a short distance away which beam their radiation, let us say two degrees away from our line of sight will be totally invisible to us.
If you calculate the depth of the Nebula in the line of site (considering that the superwave cosmic rays are travelling away from us toward the Galactic anticenter) then this calculates to d = r (1 – cos θ), where r = 4 light years, the approximate radius of the Nebula.  For θ = 1 degree this calculates to 0.0006 ly, or a depth of 0.2 light days.  So variations in cosmic ray intensity lasting 1 light day or more should certainly be reflected in gamma ray intensity variations of comparable duration.

In 1977 W. Kundt wrote that the incoherent synchrotron emission can only account for ~1% of the optical luminosity in the Crab Nebula’s wisp region and neither can it account for the 1% fraction of the optical emission which is circularly polarized.  This led him to propose that the Crab Nebula was being energized by a cosmic ray “beam” that was producing coherent synchrotron emission, the mechanism we are proposing above.  In particular, he proposed that the emission was being produced by stimulated synchro-Compton emission being beamed toward the observer.  As I pointed out in 1983 (p.177 – 179 of my Ph.d. dissertation), this emission is most likely stimulated by superwave cosmic rays propagating along our line of sight toward the Galactic anticenter and impacting the Crab Nebula.  The pulsar is an unlikely origin for the beamed emission comiing from the wisps since the vector from the pulsar to the wisps makes a large angle with respect to our line of sight.  The superwave source is left as the more plausible alternative.

Kundt, W. “The Wisps in the Crab Nebula: A Cosmic Laser?” Astronomy and Astrophysics 60 (1977):L19.


Crab Nebula flares again

Update to our previous posting about gamma ray flares being observed from the Crab Nebula, ongoing evidence that the nebula is being impacted by superwave cosmic ray electrons.

The Crab Nebula in the constellation of Taurus

BBC News story
PhysOrg.com news story

On April 12th, 2011, the Crab Nebula emitted a gamma ray flare lasting six days that was five times more intense than any of the others that were previously observed and 30 times brighter than the nebula’s normal gamma ray intensity.  On April 16th an even brighter flare occurred but faded out over a period of two days.

As stated in the previous post, I had predicted this high energy variability of the Crab Nebula almost 30 years ago in my Ph.d dissertation and in a subsequent 1987 journal publication.  It is only recently with the launching of the Swift gamma ray telescope that regular measurements of the Crab Nebula at gamma ray frequencies have been made possible.  As I proposed then, the Crab Nebula’s unusually strong luminosity does not originate from its associated neutron star but from a volley of galactic cosmic rays that are striking it face on.  Since this volley can change its intensity quite rapidly, so too the intensity of the Crab Nebula’s emission will change in step.  This would be most noticeable at gamma ray frequencies since the very high energy cosmic rays producing the gamma synchrotron radiation lose their energy quite rapidly, hence intensity changes become more noticeable than at, for example, optical frequencies where the lower energy cosmic rays have lifetimes of many years and hence smooth out any flare activity.

Current claims that the flares are attributable to the Crab’s neutron star are entirely off the mark.  In fact, there is no evidence of any correlated activity in the immediate vicinity of the Crab pulsar.  For example, NASA scientist Martin Weisskopf who was part of a team observing the pulsar with the Chandra X-ray telescope is quoted as stating:

 “Thanks to the Fermi alert, we were fortunate that our planned observations actually occurred when the flares were brightest in gamma rays,” Weisskopf said. “Despite Chandra’s excellent resolution, we detected no obvious changes in the X-ray structures in the nebula and surrounding the pulsar that could be clearly associated with the flare.”

Astronomers are currently at a loss to explain what they are seeing simply because they are ignorant of the superwave theory.  Do your part and inform them.

Gamma/X-ray source GRB 110328A still active

In response to Nick Darby’s comment on the previous post, a few days ago I checked with one of the Swift team astronomers, Jamie Kennea, who said that the source is “still well detected.” Swift observes this source daily and posts the data on the following page on their website (http://swift.gsfc.nasa.gov). Enter 110328A in the homepage search box and refer to found links. As seen from the X-ray light curve posted at http://www.swift.ac.uk/xrt_curves/00450158/, the source is still very active with no indication it is dying down, as some astronomers had expected; see graph below.

BAT X-ray intensity from GRB 110328A as of May 10, 2011

This shows that as of the date of this May 10th posting quasar source GRB 110328A has been active for one and a half months. So time is rapidly running out for the black hole snack theory. Those wishing to follow its progress on the Swift website, note that the source is also referred to as Swift J164449.3+573451.