dlzc wrote:
[...]

For the uninitiated: the article in question is "THE HARD X-RAY VIEW OF
REFLECTION, ABSORPTION, AND THE DISK-JET CONNECTION IN THE RADIO-LOUD AGN 3C
33"; D. Evans, et.al., ApJ 710 p859.

The reason I'm bothering is because of an eye raising article, I mean *press
release*, by MIT which happens to make an interesting claim about the source
of jetting for active galactic nuclei (AGN)...

MIT happens to be Evans' hosting institution.

http://web.mit.edu/newsoffice/2010/black-hole-jets.html

I'm highly interested in reading the full scholarly article
but this looks like rather speculative guessing to me. I
might go down to UW just for this.

Let us know what you find. Your shoes need to trod that ground again
anyway...

Walking to UW to borrow their institutional access to ApJ, MNRAS, Phys. Rev.
D, Science, Nature, etc is a part of my weekly ritual.

The Feb. 10 issue of ApJ was already trawled over by me, and I still have a
bunch of articles I downloaded last week that I have not yet read. But the
Evans article is not in that pile, because the blurb on the ApJ site (which
mirrors what they put on print) is not interesting.

ApJ in print form, for an entire month, is roughly 4 inches thick give or
take. The index, double sided, is six pages with a one sentence blurb about
the research. This is something people do not realize.

The observations are based on surveys by X-ray telescopes (Suzaku, XMM-
Newton, Chandra, Swift). This tells you immediately that there are no direct
observations of the region in question like how VLBI imagery directly
surveyed the area around Sgr. A*. There is nothing suspect about the
observations, as far as I can tell. Though I note with perpetual amusement
that there have to be corrections to events recorded by the satellites as
they pass through the South Atlantic Anomaly.

Speculation that there is no inner reflective surface is based on the non-
observation of the Iron-alpha emission lines. For reference, the two lines
are a 6.404 and 6.391 (from my notes..) doublet that show up rather
prominently and have been used for a very long time as a strong diagnostic
of 'what is going on' in accretion regions. Given that the AGN is only at z
=~0.03, there's an expectation of Iron being present.

Though the methodology that says there is no reflection, while not 'wrong',
is certainly up for debate.

Simple fitting of what the telescopes observe are consistent with a power
law spectrum that has some absorbing properties. No big surprise there -
power law spectrae are par for the course when it comes to astrophysics, and
absorbing of light is not a shocker when it comes to ionized locales.

What a straight reading of this one piece of scholarly research does not
indicate is that there is a super, super, SUPER strong coupling between the
inclination angle of the accretion disk and what is observed on Earth.
Furthermore, even a reasonable fit on the angle is ****ing hard to make even
for close and cooperative regions in which a wide variety of wavelengths are
available. So when Evans assumes a 60 degree angle for the inclination,
without sourcing it, it raises an eyebrow.

Also, Evans uses a simulation called 'reflexionx' for modeling the X-ray
spectrum. That raises another eyebrow because in "Measuring the spin of
GRS1915+105 with relativistic disk reflection"; J. Blum et.al., ApJ 706 p60
(the subject should tell you this ties in), it was found that the reflexionx
model was giving results for the spin parameter that were inconsistent with
previous works on the subject using equivalent data sets. So I'll smack
anyone who makes a serious argument using this paper's interpretations of
the data unless some very fancy footwork is done.

This tells you everything you need to know:

"Our results demonstrate that 3C 33 shows no signs of Compton
reflection from neutral material in the inner regions of an
accretion disk: there is no reflection hump at energies 10 keV,
and no evidence for relativistically broadened Fe K? emission
(Model VII)."

I fully expect that the inner part of accretion flow is mostly plasma, and I
thought that before it was later pointed out that all the data is consistent
with an ionized accretion flow.

The thing that I really, really wanted to see was a substantiation of the
claim that retrograde accretion flow with respect to the spin of the black
hole could *happen*, and explain what's seen.

"The X-ray spectrum of 3C 33 is also consistent with the picture
of Garofalo et al. (2009). They argue the jet power of high-
excitation radio galaxies such as 3C 33 is the result of
retrograde black-hole spin with respect to the accreting material.
This configuration results in a larger innermost circular stable
orbit than for a prograde black hole. The weak or absent
signatures of reflection in 3C 33, then, are simply a consequence
of the large inner disk radius."

My opinion on this has not changed. At all. I do not see how it is
physically possible, much less plausible.

Furthermore, the direction in which a Kerr black hole rotates has an
abundance of ****-all to do with the radius of the innermost stable orbit
for massive particles. So it is my very, very strong personal opinion that
the claim that a black hole spinning in one direction versus another
direction has anything to do with the location of the innermost stable
circular orbit.

I really, REALLY wanted to read Garofalo (2009), but it doesn't exist. I'm
substantially irritated that the only substantiation of the theory was a one
paragraph blurb that references an article that doesn't exist yet.

"Garofalo, D., Evans, D. A., & Sambruna, R. M. 2009, MNRAS,
submitted"

That Evans is second author on that reference makes me wonder ever so
slightly. Especially since not once in my ever-larger reading on this
subject have I ever seen the idea that retrograde accretion flow can exist,
much less do what is claimed.

I've made a note in my notebook on this, and I'll keep a lookout for the
article in MNRAS but I'm highly skeptical at this point.

People sometimes wonder how the time I spend on this newsgroup manifests
itself. This oughta clear that up.


David A. Smith