Update on the spectroscopic changes at ingress

Thank you for posting this data !!! Is the possible accomplice being a little shy :-) The workshop was fantastic, Hopefully you can make it to the next one !!! Have a good weekend. ~~~ PJ aka Spaceblanket

Hi Robin, Iam extremely pleased at the high quality of your spectra and your coverage of the last few months! A couple of questions for you: 1)If the brightness variations of eps Aur are due to radial pulsations, shouldn't the line centre and shape change with time - on the 60 to 160 day timescales seen in the brightness? 2) In the absence of pulsation of the primary and/or disk rotation of the secondary, there should be no relative radial velocity difference between the secondary and primary gas. Are the KI features supposed to be related to the gas flowing from primary to secondary?If so, that should appear blue-shifted relative to the line of the primary.(Of course, if the centre of the primary KI line is moving around due to pulsation, that would make analysis more complex.) Cheers and keep up the great work! Doug

Hi Doug, Thanks for your kind comments. Your questions areprobably more in Dr Bob's area than mine but this is the information I have gleaned from the literature:- 1) There is evidence that the KI line outside eclipse may in fact be mainly interstellar in origin rather than from the primary. For example theirappears to be no radial velocity change in the line from pre to post eclipse seen in Lambert and Sawyer's data from the last eclipse despite the ~5km/secblueward change seen in lines known to be from the primary photosphere andassumed to be due to the orbital velocity and the system geometry.Also very high resolution spectra of the line outside eclipse show three separate components which may be indicative of separate interstellar clouds. (Welty and Hobbs THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 133:345»393, 2001 April)

It might be possible to follow any primary radial pulsations outside eclipseusing other lines which are known to be from the primary photosphere. I am not sure if the RVchangesat that sort of period would be large enough to be detected by an amateur spectrograph though. I would need to run some numbers. For information here is an example of radial pulsation detection of a shorter period star by an amateur. (RRLyrae by Christian Buil)

http://www.astrosurf.com/buil/rrlyr/obs.htm 2) The doppler shift of the additional KI line component seen last eclipse by Lambert and Sawyer began red shifted by ~20km/sec at 1st contact and moved smoothly toa ~40km/sec blue shift by 4rd contact. See the RV graph posted here. http://www.citizensky.org/sites/default/files/Fig%2027_0.gif Thisis consistent with the absorptionbeing producedby a rotatingdisc of materialpassing in front of the primary. The material producing the KIabsorption may extend beyond more opaquematerial which produces the photometric eclipse.This would explain thepresence of the KI additional absorption componentfor some time before and after the eclipse. Cheers Robin