EB Working Group Charter



Eclipsing binary stars are the cornerstone of stellar astrophysics: their unique geometry allows us to derive the fundamental stellar parameters – temperatures, radii, masses and luminosities – of the binary system components. This unique property, contrasted with other means of determining stellar radii that either apply to only a handful of objects (such as resolving the disk of a star) or are encumbered with a larger uncertainty (i.e. P–L–R relationships), promoted eclipsing binaries as calibrators of stellar properties. Binarity allows us to determine the masses of individual components, and the alignment of a system’s orbit with the line of sight and subsequent eclipses allow us to determine their radii to better than a few percent (Andersen 1991; Torres et al. 2010). To perform such accurate modeling, we need to acquire both photometric and spectroscopic observations. From Kepler photometry we can obtain the relative sizes of both components and their temperature ratio; for individual temperatures we require calibrated multi-band photometry, and for masses and an absolute scale of the system we require spectroscopy. Having these data available, modeling yields the fundamental parameters of the system components that are used to calibrate stars across the H-R diagram (Harmanec 1988), determine accurate distances (Guinan et al. 1998) and study a range of intrinsic phenomena such as pulsations, spots, accretion disks, etc. (Olah 2007).

The Kepler Eclipsing Binary working group is established to promote collaboration and communication within the binary star community interested in reducing, analyzing and modeling Kepler data. This includes acquiring follow-up observations, applying the methods from other fields (i.e. from asteroseismology, exoplanetary science, celestial dynamics, general relativity), and working towards achieving the working group tasks.


Main Working Group Tasks


Kepler's core objective is to detect and characterize extrasolar planets, with special emphasis on the occurrence rate of Earth-sized planets in the habitable zone (𝜂Earth). To support the core Kepler mission, the Eclipsing Binary Working Group assumes the following tasks, in order of priority:
  • maintain a catalog of eclipsing binaries in the Kepler field, including their ephemerides, the derived properties via automated methods, the geometric properties (eclipse widths, depths and separations), and any additional signal (ellipsoidal variability, eclipse timing variations, tertiary events, multiple periodicities) and to find statistical properties of EBs: spatial distributions, multiplicity and orbital properties (eccentricity distributions);

  • detect, validate and analyze circumstellar and circumbinary planets via tertiary events and eclipse timing variations; and

  • determine the occurrence rate of false positives in the KOI catalog, including background (faint) eclipsing binaries that contaminate the target's aperture as well as foreground (bright) eclipsing binaries that bleed into the target's aperture.
Working Group members are expected to contribute to these core tasks.


Other Working Group Tasks


Beyond these core goals, the members of the Working Group are involved in the supplementary goals. These are either individual projects or they can contribute to the core goals.
  • conduct an extensive photometric and spectroscopic follow-up effort to obtain colors, spectra and radial velocities for the Kepler sample of EBs;

  • characterize fundamental physical properties of EBs in the Kepler data-set via precise modeling of Kepler light curves, follow-up photometry and spectroscopy. This is conducted towards two primary goals: (1) determining the mass-radius relationship for low-mass stars where there is a known discrepancy between models and observations, and (2) using the masses and radii of Sun-like stars obtained from EB modeling to compare them to those obtained from asteroseismology; when good agreement is reached, calibrated asteroseismic methods may be used to obtain masses and radii of single stars (crucial for planetary systems where the size of the host star determines the sizes of orbiting planets);

  • study stellar multiplicity: tertiary components, orbital evolution, circularization and synchronization;

  • study intrinsic variability associated with either or both binary system components, such as chromospheric activity, tidally induced oscillations, free body pulsations, pressure and gravity modes, and granulation effects;

  • understand dynamical interactions between components, including disruption due to third body encounters, orbital tightening via Kozai cycles, phase locking, mass transfer and common envelope stages;

  • develop sophisticated modeling codes that enable the analysis of second-order effects in Kepler light curves that have thus far been largely ignored, such as Doppler beaming, spin-to-orbit misalignment, differential rotation, deviations from the Roche equipotentials etc;

  • understand selection biases, systematics and instrumental artifacts of the Kepler data-set.
The supplementary goals are subject to change and refinement and follow individual interests. There is no limitation to adding any personal goals that are not listed above. The core task of cataloging EBs allows for cherry-picking targets with the most promising scientific yield.


Working Group Communication


The main communication is done via the mailing list:

https://lists.nasa.gov/mailman/listinfo/kepler-eb

All members are strongly encouraged to join the mailing list. Subscriptions should be done with a full name and an institutional email. Confirmation is necessary and might take up to 3 days. Please note that all communication is archived and the archives are accessible to all working group members, present and future. All emails to the mailing list must be treated as confidential since sensitive information is discussed and disseminated on a regular basis. To keep the communication open and unhindered, never copy or forward emails to non-members. Please also refrain from posting any programmatic issues and concerns you may have; instead, those should be directed to the Steering Committee.

Working Group's weekly telecons are every Monday at 3pm EST (8pm GMT) and go for 1 hour. The telecons are open to all members. The dial-in information, weekly agenda and minutes are posted on the mailing list.


Publication Policy


The publications that arise from collaborative effort within the Working Group need to follow the basic policy: the first author is the person who led the project from conception to fruition and wrote the bulk of the paper, or the person who was selected by the co-authors to take the lead based on substantial merit. All co-authors must send in a statement that:
  1. they have read the manuscript and agree with the applied methods and conclusions, and
  2. clearly state their contribution to the paper or the mission. Co-authorship based on merit to the mission (i.e. engineering/software work, science office operations, etc) is most welcome and strongly encouraged.


Organizational Structure


EB Working Group is built on open communication, open access and the free flow of data and information. To promote the work towards achieving the main science goals of the working group, a formal structure of the Working Group is organized that consists of:

  • EBWG Chair. The role of the Chair is to serve as a point of contact for the Working Group, to organize the telecons, set up relevant agenda and ensure that the main Working Group tasks are being met. The Chair is elected every 2 years.

  • EBWG Steering Committee. The Steering Committee is tasked to overview the projects, goals, progress and effort towards achieving the core tasks. The Committee consists of the EBWG Chair and 4 EBWG members who are elected from the EBWG membership for a two year term. The Committee reviews membership applications and has authoritative power in case of disputes or violations of the rules of conduct.

  • EBWG KEC Representative. The Kepler Exoplanet Council provides scientific input to the Kepler project. The KEC Representative is a member who acts as a liaison between the Working Group and the Council. The role of the Representative is to serve as the point of contact within the Kepler project: to report the EBWG activities to the Project and to summarize the deliberations of the Project to the EBWG through telecons and/or the mailing list.

  • EBWG membership. Any individual or a group from the broad scientific community may apply for membership in the EBWG. The applications are reviewed by the Steering Committee. An application is an electronic letter that contains the following:

    1. the statement that the applicant has read and agrees with the provisions in the EB Charter;
    2. scientific background, current position and contact information;
    3. research interests and expertise;
    4. expected contribution to the EBWG's goals.

    The membership applications should be sent to the EBWG Chair, who forwards the request to the EBWG Steering Committee. Applications are reviewed and the applicants are typically notified within 1 week of application receipt. The list of members is public and can be accessed here.


Membership Policy


  1. Collaboration and the open exchange of information is vital to the success of the EBWG. To facilitate complete and timely sharing among WG members, members agree to protect all intellectual property shared at telecons, in meetings, via e-mail exchanges, etc. The intent is not to limit information exchange but to enable it. Information is to be taken in its broadest context; it includes data, results, figures, text, code, ideas, plans, goals, speculations, etc.

  2. Members are encouraged to work on whatever project interests them, but they also have a responsibility to contribute to the EBWG's core goals and support the Kepler Extended Mission objectives. While volunteers are always solicited first, on occasion tasks may be delegated to members. Such tasks may be very minor (e.g. taking notes during the EB telecons) or substantial (observing, writing proposals, leading a study).

  3. When a member wishes to lead an investigation, it is their responsibility to make the scope of the project known to the EBWG before the project starts, and to post the information so that others in the EBWG can view it. Others can then offer to contribute to the investigation at the start. Status reports of the investigation are expected. Others may join the investigation at any time, with the only constraint being that they contribute something significant to the project. In general, there is no limitation on numbers of authors on EBWG papers. If a member decides that they no longer wish to lead an investigation, or that time constraints do no permit a timely completion of the paper, the investigation should be offered to others. If two or more members wish to lead the same investigation, every effort will be made by the Steering Committee to fairly decide who will run the investigation and be lead author.

  4. Disputes will be resolved by the EBWG Steering Committee. Violation of the standards for professional behavior will result in dismissal from the EBWG. Improper conduct includes: attempting to publish, present results, or submit proposals independently of the EBWG if they are based on information presented to the EBWG; sharing information with non-EBWG team members without the consent of the EBWG.