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Fraser
2010-Apr-11, 09:00 PM
"The most exciting phrase to hear in science, the one that heralds new discoveries, is not Eureka! (I found it!) but rather, 'hmm… that's funny…'" (Isaac Asimov) A few short years ago, Zooite Hanny van Arkel discovered Hanny's Voorwerp in an SDSS image of a galaxy ("What's the blue stuff below? Anyone?"), and a new term [...]

More... (http://www.universetoday.com/2010/04/11/mitchs-mystery-star-curiouser-and-curiouser/)

John Jaksich
2010-Apr-11, 09:13 PM
Thanks for the post, Fraser

ngc3314
2010-Apr-12, 01:23 AM
I should also point out that we've had very interesting input from Zooite eigenstate, experienced in high-resolution molecular spectroscopy, regarding possible identifications for a spectral band (as far as I know not yet identified) which is very prominent around 6100 A and has all the hallmarks of a molecular feature.

I remember that line from Asimov from many years ago. May or may not still have the book downstairs...

EigenState
2010-Apr-16, 03:22 AM
Greetings,


I should also point out that we've had very interesting input from Zooite eigenstate, experienced in high-resolution molecular spectroscopy, regarding possible identifications for a spectral band (as far as I know not yet identified) which is very prominent around 6100 A and has all the hallmarks of a molecular feature.

Interesting is one thing, relevant quite another. I can only hope that my thoughts have contributed in some positive manner.

I must agree that the asymmetry on the blue wing of the 6100A band appears to be congestion characteristic of rotational band heads. I have yet to come up with what I consider reasonable candidate molecules, although I admit that I only seriously thought about diatomics. The lack of any apparent vibrational bands is curious to me as well.

Best regards,
EigenState

slang
2010-Apr-17, 05:02 PM
Welcome to BAUT, EigenState!

trinitree88
2010-Apr-17, 05:35 PM
I should also point out that we've had very interesting input from Zooite eigenstate, experienced in high-resolution molecular spectroscopy, regarding possible identifications for a spectral band (as far as I know not yet identified) which is very prominent around 6100 A and has all the hallmarks of a molecular feature.

I remember that line from Asimov from many years ago. May or may not still have the book downstairs...


ngc...I resemble that remark. Actually, I'll take a wild guess. I've been looking for a strange star for a while. Here's the rationale. Just as the occasional passage of a star through our Oort cloud can disrupt orbits and send a rain of comets later on into the inner solar system, the passage of a pulsar can disrupt planets and their moons, raining them in on their host star. This is not a highly likely scenario, but with the kinematics of pulsars being such that the majority of them are ejected from their host progenitors with velocities that do not exceed galactic escape velocity (~400 km/sec), and with most type 2's in a galaxy having their axisymmetric orientations related to the host galaxy's magnetic field, we can expect a circulation of ~ 100,000 pulsars intermittently through the galactic disk and perpendicular to it. (I draw the numerical inferences from ~ 30 years of reading supernovae articles, and the numbers may be off by ~ a magnitude with contemporay searches of the data, but the principles I believe are physically coherent). With the universe being a big place, that which is not forbidden, will eventually occur, hence a planet or Earth-like moon will be thrown into Roche limits with it's host star....possibly into a white dwarf. What will that produce as a result? The salt in the putative ocean will show up as an emission feature initially during the merger, and then as some of it ends up the white dwarf's atmosphere, as an absorption feature. Note that the spectrum has a distinct signature of both potassium and sodium, and chlorine,with a characteristic absorption feature of NaD just blueward of 6000A. In addition, the metallic Earth-like core could be making the strong absorption at ~ 6100A by FeIII, and 13 ionized iron gives our sun a weak green flash, but a lot more iron would make Hanny's green optically. (Fillipenko, SEE:http://arxiv.org/abs/astro-ph/9907172). Wild enough? Hence, Hanny's Voorwerp. pete

...and you thought the Death Star in Star Wars was bad, this baby could have been populated..

EigenState
2010-Apr-17, 07:19 PM
Greetings,

Thank you slang for the kind welcome.


Note that the spectrum has a distinct signature of both potassium and sodium, and chlorine,with a characteristic absorption feature of NaD just blueward of 6000A. In addition, the metallic Earth-like core could be making the strong absorption at ~ 6100A by FeIII

There is little doubt regarding the presence of absorption features that can be assigned reliably to NaI and KI. To me, the assertion that there is a distinct signature indicating the presence of chlorine remains highly problematic. Perhaps you would be kind enough to indicate the wavelength(s) for that assignment.

I am highly suspect of the presence of Na2H. Based upon data supplied to the discussions at the GalaxyZoo forum, Professor Dufour indicated that the stellar atmosphere is strongly dominated by He, with an H abundance of the order of 10-3 that of He. Those relative population densities make it difficult to comprehend an abundance of Na2H sufficient to cause an absorption feature as strong as the one observed.

To avoid any ambiguity, the recent discussions at the GalaxyZoo forum relevant to the star in question have focused on attempts to understand the asymmetry in the feature in the region of 6100. Barring consideration of data not yet available to me, I must agree with my friend ngc3314 that the band in question does indeed show the "hallmarks of a molecular feature" in that it appears totally consistent with rotational band head congestion. I also admit that I have proposed an alternative hypothesis focused on collisional broadening.

Best regards,
EigenState

trinitree88
2010-Apr-20, 07:50 PM
Greetings,

Thank you slang for the kind welcome.



There is little doubt regarding the presence of absorption features that can be assigned reliably to NaI and KI. To me, the assertion that there is a distinct signature indicating the presence of chlorine remains highly problematic. Perhaps you would be kind enough to indicate the wavelength(s) for that assignment.

I am highly suspect of the presence of Na2H. Based upon data supplied to the discussions at the GalaxyZoo forum, Professor Dufour indicated that the stellar atmosphere is strongly dominated by He, with an H abundance of the order of 10-3 that of He. Those relative population densities make it difficult to comprehend an abundance of Na2H sufficient to cause an absorption feature as strong as the one observed.

To avoid any ambiguity, the recent discussions at the GalaxyZoo forum relevant to the star in question have focused on attempts to understand the asymmetry in the feature in the region of 6100. Barring consideration of data not yet available to me, I must agree with my friend ngc3314 that the band in question does indeed show the "hallmarks of a molecular feature" in that it appears totally consistent with rotational band head congestion. I also admit that I have proposed an alternative hypothesis focused on collisional broadening.

Best regards,
EigenState

Eigenstate. My humbles. I glanced at the area near ~ 6300 and ~ 6375 and mistook the OI for a blurry Cl on my monitor. To err is human..... pete

EigenState
2010-Apr-20, 08:07 PM
Greetings,


Eigenstate. My humbles. I glanced at the area near ~ 6300 and ~ 6375 and mistook the OI for a blurry Cl on my monitor. To err is human..... pete

Not a problem, and it is not easy to read the SDSS spectrum. If I am correct that you are referring to that small blob, I do not think it is OI either, but based on the synthetic spectrum a weak CaI transition.

I should apologize for using the word "blob", but to me these spectra are exceedingly low resolution--I do sub-Doppler stuff.

Best regards,
EigenState

EigenState
2010-Oct-29, 06:19 PM
Greetings,

A progress report: The cool end of the DZ sequence in the SDSS (http://arxiv.org/abs/1010.4698). Detlev Koester, Jonathan Girven, Boris Gaensicke, Patrick Dufour, to appear in the proceedings of the "17th European Workshop on White Dwarfs", Tuebingen, Germany, August 16-20, 2010.

In that discussion, Mitch's Mystery Star is SDSS0916+2540. Regarding a possible explanation of the asymmetrically broadened 6100 line profile:


The CaI and CaII resonance lines between 3900 and 4250 A are so strong that they completely cut off all the flux below 4500 A. Our profiles assume a van der Waals r−6 dependence for the perturbation energy, which has been shown by [6] to be a very poor approximation for the Ca-He interaction. This assumption has to be replaced by a more sophisticated potential for each individual line. The current profiles are not a satisfactory approximation.

Although details are missing from the discussion, this appears to be a state-selective, collisional broadening mechanism as first proposed at the GalaxyZoo forum.

Best regards,
EigenState