Forums / The Science / Data Analysis / First Publication: CBET #1885!

First Publication: CBET #1885!

Citizen Sky is now officially permanent part of the AAVSO. In the coming weeks we will be moving additional content to the AAVSO site and freezing this site as an archive of the 1st three years of the project. Please visit the new landing page for future updates.
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On July 27, 2009 the IAU's Central Bureau of Astronomical Telegrams (CBAT) issued a Central Bureau Electronic Telegram (CBET) announcing our most recent observations. CBAT is located at the Harvard-Smithsonian Center for Astrophysics and is charged by the IAU to distribute important announcements and discoveries to the scientific community. The discoveries are usually time sensitive so can't wait for a formal paper to be written and published in a journal. CBAT has two publications they can use for stellar discoveries: the IAU Circular and the CBET. The latter is issued more frequently, so is used when timing is critical. Both are publications of record in the astronomical community.

Thus, CBET #1885 is the first publication of the Citizen Sky project! Congrats to Robin and all the observers who submitted data for the publication. It is important to let the rest of the community to know that the eclipse may have begun (in some wavelengths). Many astronomers are interested in this star so they now begin scheduling observations and paying closer attention to the star.

As activity commenses, we may submit other reports to CBAT. We can't guarantee they will publish them - CBAT is a referee'd publication. But we will send reports of important events that our participants detect. Also, when an event is reported, CBAT also likes to report latest observations of the star. I believe this is intended to  help astronomers plan their observations. You can see an example of such a list at the bottom of this CBET. So don't be surprised if one of your regular observations makes it into the publication.

                                                  Electronic Telegram No. 1885
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://www.cfa.harvard.edu/iau/cbat.html

EPSILON AURIGAE
     E. O. Waagen, AAVSO, writes that R. Leadbeater, Wigton, U.K., reported
(via the AAVSO Discussion Group) the spectroscopic detection of the start of
a predicted eclipse for the long-period binary star epsilon Aur.  The last
eclipse was in 1982-1984.  A redshifted component in the K I 769.9-nm line
has appeared in LHIRES III observations obtained on July 20.081 UT, offset by
+15 km/s and with 62-mA equivalent width.  This emerging feature is uniquely
associated with eclipse phases, wherein visual light declines by 0.75 mag
over 18 months.  Information on the international epsilon Aur eclipse
campaign may be found at website URL http://www.citizensky.org.  Selected
visual magnitude estimates submitted to the AAVSO International Database:
Apr. 28.818 UT, 2.9 (M. Rzepka, Krosno, Poland); May 23.233, 2.9 (P. Abbott,
Leduc, Alberta, Canada); June 21.924, 2.9 (V. Makela, Helsinki, Finland);
July 3.078, 2.9 (S. Baroni, Milan, Italy); 22.035, 3.0 (P. Maurer, Bad
Friedichshall, Germany).  H and J magnitudes submitted to the AAVSO
International Database:  Apr. 24.022, J = 1.77 (B. McCandless, Elkton, MD,
U.S.A.); 24.043, H = 1.50 (McCandless); May 13.053, J = 1.83 (T. Rutherford,
Blountville, TN, U.S.A.); 13.065, H = 1.53 (McCandless); 30.06, J = 1.85,
H = 1.61 (Rutherford).  BVRI magnitudes submitted to the AAVSO International
Database:  Apr. 24.07, V = 2.92, R = 2.51 (McCandless); 24.078, B = 3.45
(G. Samolyk, Greenfield, WI, U.S.A.); May 13.055, R = 2.38 (McCandless);
July 3.961, V = 2.87, I_c = 2.21 (R. Miles, Stourton Caundle, Dorset,
England); 20.026, I_c = 2.33 (Miles); 20.044, V = 3.03 (Miles).

NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.
                         (C) Copyright 2009 CBAT
2009 July 27                     (CBET 1885)              Daniel W. E. Green

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Those interested canview the spectra that show the contribution from the eclipsing object on my website here www.threehillsobservatory.co.uk/astro/spectra_40.htm Robin

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Hi Robin, Can you please explain for us what there is about the spectrum that indicates the start of the eclipse? I know the spectrum changed, but I have seen significant changes in other areas of the spectrum well out-of-eclipse. Thanks.

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Hi Jeff, Yes variations independent of the eclipse are a potential problem, particularly in lineslikeH alpha which has components due to circumstellar material as well as fromthe primary star itself. To be able to estimate what changes can becanattributedto absorption by the eclipsing secondary we need good coverage pre and post eclipse. The KI line (which out of eclipsemay either be from the primary star or may becaused byinterstellar material between us and the star) has varied slightly in intensity on the run up to the eclipse but the shape of the line and its wavelength has been essentially constant. An explanation of what we are seeing now is the appearance of an additional componentfromabsorptionby the leading edge of the eclipsing object as it crosses in front of the primary star. Because the eclipsing object is rotating, the leading edge has a velocity component away from us, relative to the primary star.This causes the additional contributionto bered shifted due to the Doppler effect. (Measuring this in the spectrum, it works out at a velocity of 19km/sec) You can see anestimate of the primary/interstellar and eclipsing object contributions to the KI line as of 19/20th July hereon my website. http://www.threehillsobservatory.co.uk/astro/epsaur_KI_19jul09_components_heliocor_normcontin_annot.png As the eclipse progresses, the new componentwould beexpected to strengthen and then shift to the blue side of the line as thetrailing edge of the eclipsing object moves in front of the star, similar to the changesseen by Lambert and Sawyer during the last eclipse. http://adsabs.harvard.edu/abs/1986PASP...98..389L Ihope I have got this right. If notI am sure Dr Bob will put us straight It looks like spectroscopy has turned out to be a more sensitive tool than broad band photometry in detecting the presumably tenuous outerregions of the eclipsing object.Photometric changes are likely to be imminent though.

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Great work Robin! Jeff

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