rainbow
Non-stationary surface structures of CP stars
   published by O. Kochukhov and N. Piskunov
exciting discovery or "technical problem" ?

rainbow


December 3, 2021

It has been well known for some time -- published in high-impact refereed journals although
initially rejected by A&A -- that Zeeman Doppler mapping (ZDM) suffers from a number of
problems. These include imagined abundance spots (Lueftinger et al. 2010a, laid bare by
Stift & Leone 2016), physically impossible abundances (Nesvacil et al. 2012, exposed by
Stift & Leone 2017), non-uniqueness (shown by Stift & Alecian 2009, Stift & Leone 2017),
tests based on breathtakingly artificial magnetic geometries and simplistic distributions
of abundance spots or rings, and the complete lack of theoretical and/or empirical arguments
underpinning many of the key assumptions underlying ZDM.
 
In addition to these serious shortcomings I found yet another error in ZDM papers spread
over 8 years: spots and magnetic fields of CP stars (and in test cases) shifting in longitude.
By no less than about 30 degrees over a whole rotation !! I deemed my findings
disturbing enough to contact the editors of A&A on 12-03-2021, writing the following

Dear editors of A&A,

I recently had a close look at the paper on HD24712 by Lueftinger et al. (2010). All
the Figs. 1, 2, 5, 6, 7, 8 suffer from the same serious problem: the spots are shifting
in longitude from one phase to the next, and so does the strong magnetic pole! This
shift occurs for all elements. The effect is quite easy to detect, at high resolution
(800%) it cannot possibly be missed.

I started to wonder whether this surreal shift was unique to this article but I soon
found several other instances of these strange field and abundance shifts in longitude.
They can already be found in the 2002 A&A paper by Kochukhov & Piskunov, where the
spots used for the tests exhibit substantial longitude changes. They are obvious again in
the A&A paper on 53Cam by Kochukhov et al. (2004), concerning both magnetic field and
abundance spots. Piskunov (2008, Phys.Scr.) also presents changeable spots for 53Cam.
2 images downloaded from Kochukhov's homepage some time ago, viz. 53cam_abn.jpg
and alpha2CVn_abn.jpg in the attachments, feature these strange shifts too.

It is difficult to understand what happened with these maps. Are we faced simply with
a programming error in the plot -- running undetected for at least 8 years (!!) -- or does
the problem run much deeper, involving the inversion itself?

In the interest of scientific probity, A&A should clarify this issue immediately.

After almost 9 months, there has not been the slightest trace of a reaction from
A&A. Shouldn't one expect the major continental European astronomical journal to
speedily investigate such visible, embarrassing, potentially devastating flaws
(oddly enough left undetected for 8 years by the referees of the incriminated
3 A&A articles)?


Notes added:
During these 9 months I have in July 2021 discovered another 2 papers by Kochukhov
with those strange shifting spots. "Non-stationary" spots in HR3831 have been
published by Kochukhov et al. (2003). Tests with shifting spots -- and poor recovery
of these (!) -- are due to Kochukhov (2004).
Towards the end of November 2021 I have become aware of yet another disconcerting
occurrence of shifting spots, presented in a lecture on "Surface cartography of the
Sun and stars", Besancon, 2014. Slide 20, not quite appropriately titled "Stability
of Ap-star spots", reveals -- at each of the 4 epochs shown -- startling changes
with phase in the positions of the spots on 56 Ari. How is it possible that such a
"discovery" or "technical problem" could persist for a staggering 12 years, not
being noted by any of the referees and editors involved?

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