Epsilon Aurigae - Two Year Totallity TranspiringBrian Kloppenborg,1 Robert Stencel,1 Jeffrey Hopkins2

1University of Denver, Dept. of Physics and Astronomy; 2 Hopkins Phoenix Observatory

Abstract

The 27 year period eclipsing binary, epsilon Aurigae, exhibits the hallmarks of a classical Algol system,except that the companion to the F supergiant primary star is surprisingly under-luminous for its mass.Eclipse ingress appears to have begun shortly after the predicted time in August 2009, near JD2,455,065. At the University of Denver, we have focused on near-infrared interferometry, spectroscopy,and photometry with the superior instrumentation available today, compared to that of the 1983 eclipse.Previously obtained interferometry indicates that the source is asymmetric (Stencel, et. al. 2009 APLJ)and initial CHARA+MIRC closure-phase imaging shows hints of resolved structures. In parallel, we havepursued SPEX near-IR spectra at NASA IRTF in order to confirm whether CO molecules only seenduring the second half of the 1983 eclipse will reappear on schedule. Additionally, we have obtained Jand H band photometry using an Optec SSP-4 photometer with a newly written control and analysissuite. Our goal is to refine daytime photometric methods in order to provide coverage of the anticipatedmid-eclipse brightening during summer 2010, from our high-altitude observatory atop Mt. Evans,Colorado. Also, many parallel observations are ongoing as part of the epsilon Aurigae internationalcampaign. In this report, we describe the progress of the eclipse and ongoing observations. We inviteinterested parties to get involved with the campaign for coverage of the 2009-2011 eclipse via thecampaign websites.

ε Aurigae Campaign

The international campaign on epsilon Aurigae consists of more than 50 professional and amateurastronomers. The individuals in this collaboration are conducting photometry in a wide array of filters,high and low resolution spectroscopy, polarimetry, and interferometry all with the goal of solving themystery of ε Aurigae. Below we highlight the photometric and spectroscopic data products to-datefrom the campaign.

Photometry

One of the primary efforts of the campaign has resulted in coverage of the eclipse in 10 photometricbands. The data below were provided by Jeffrey Hopkins (UBV) and Brian McCandless (RIJH plusWingABC) and are representative of the extensive photometric coverage during this eclipse cycle.

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Spectroscopy

Several observers are pursuing spectroscopic observations of ε Aur in order to create a longitudinal mapof the eclipsing disk. The spectra and equivalent widths, provided by Robin Leadbeater, show the firsthints of the eclipsing body having regions of differing composition. The photometry by Jeffrey Hopkinsshows an interesting detailed anti-correlation with the KI 7669 EW variation. The individual line profileobservations are shown (right) with Julian date labels.

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SSP-4: Near Infrared Photometry

A new control and analysis suite for Optec’s SSP-4 J and H-band photometer has been programmed byB.K. for the purpose of reliably observing ε Aurigae during the daytime of summer 2010 from our highaltitude observatory atop Mt. Evans. The software and database are available from the website listed inthe bottom-right corner of this poster.

The new control software unleashes the full capabilities of the photometer featuring:

I Integration times between 0.01 to 65.53 seconds in 0.01 sec. increments

I A virtually unlimited number of exposures per scan set

I The Average and Standard Deviation are displayed on screen after each scan

I The ability to add lengthy comments in the data file

I Logging of the detector’s temperature

I Programming that is resilient to losing the connection with the camera (lose wires, etc.)

I Cross-platform compatibility (Windows, Mac, Linux)

New Analysis Software

The new control software and daytime observations precipitated the development of new reductionsoftware. This software, written in Python, will eventually be ported to Java and integrated withAAVSO’s new VStar application.

The new reduction software features:

I Conversion routines from Optec’s format to the new data format

I Automatic dark and sky subtraction using linear regression (for daytime observations)

I Full uncertainty analysis

I Integration with the new JHK calibration database, nearly automatic lookups for calibration stars

JHK Calibration Database

Full uncertainty analysis requires well-characterized calibrators, therefore B.K. transformed the UKIRTbright star catalog into the MKO-NIR filter set, which closely resembles the SSP-4’s filter profiles. Thedatabase consists of 322 stars with magnitude ranges of -3.11 to 6.8 in H and -2.33 to 6.91 in J.

ε Aur Long Term Photometry

ε Aur has been monitored nearly continuously by Louis Boyd and Jeffrey Hopkins since the 1983 eclipsein the U, B, and V photometric bands. Their data is plotted at the bottom of this poster. Gaps are dueto sun avoidance periods in the summer. We using this data to constrain the periodicity of theout-of-eclipse variations. The plots below are weighted wavelet transforms of their data showing that εAur has no dominant period. The changing of periodicity is being investigated further.

ε Aurigae Phase

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Citizen Sky: citizensky.org

R.S. and B.K. are science advisers to the Citizen Sky project, funded under the informal scienceeducation program of the NSF. This project welcomes everyone to become a citizen scientist and equipsour members with the skills and knowledge to conduct variable star observations, analyze the data, andpublish the results in a scientific journal. At present over 1,000 participants have signed up. Weencourage you to get involved and check out the Citizen Sky posters at AAS:

Tuesday 215.03 - Citizen Sky, IYA 2009 and Whats To Come

Wednesday 467.06 - Citizen Sky, Solving the Mystery of epsilon Aurigae

Wednesday 467.07 - Statistical Software Development as an Example of a Citizen Sky Participant Team

CHARA - Interferometric Imaging

The ε Aur Interferometry Team used the MIRC four-telescope beam combiner at the CHARA array toobtain high-resolution (0.5 milliarcsecond) images of epislon Aurigae during autumn 2009. Theseimages and a model for the eclipsing body will be discussed in an upcoming paper. The UV planecoverage for (UT) Nov. 2-4 and Dec. 2-4 are plotted below.

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The eps Aur Interferometry Team consists of Kloppenborg, B.1, Stencel, R.1, Monnier, J.2, Schaefer,G.3, Zhao, M.4, Baron, F.2, McAlister, H.3, ten Brummelaar, T.3, Farrington, C.3, Pedretti, E.5,Sallave-Goldfinger, P.3, Sturman, J.3, Sturman, L.3, Thureau, N.5, Turner, N.3, Che X.2, and Carroll,S.6 from 1The University of Denver, 2The University of Michigan, 3CHARA/Georgia State University,4JPL, 5The University of St. Andrews, Scotland, UK, and 6The California Institute of Technology.

IRTF - IR Spectroscopy

In order to better characterize the eclipsing body in the ε Aur system, two of us (B.K. and R.S.) havepursued infrared spectroscopy at NASA IRTF. Our observations span 0.5 µm to 5.0 µm at R=2500.

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The continuum has been left in the spectra in order to show the clear decrease since the onset of theeclipse. The 2009 Jan. 01 observation was conducted eight months before ingress was detectedphotometrically. These observations are being used to create a longitudinal map of the disk’s structure.Related observational monitoring is underway with BASS and MIRSI by Michael Sitko, with MIRAC byJoseph Hora, and with 2SPEC by William Ketzebak and collaborators.

Acknowledgements

The University of Denver participants are grateful for the bequest of William Hershel Womble in supportof astronomy at the University of Denver. The authors are grateful to Robin Leadbeater and BrianMcCandless for permitting their data to be displayed on this poster.Please see the ε Aur campaign websites at: http://www.hposoft.com/Campaign09.html andhttp://www.du.edu/∼rstencel/epsaur.htm

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Brian.Kloppenborg@du.edu https://portfolio.du.edu/bkloppen