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The variation in brightness of an eclipsing binary is described by its light curve. This is a graph of how its brightness changes with time. A light curve typically graphs some measure of brightness on the y-axis -- either flux or magnitude. The x-axis uses a variable called phase.

This is a number between 0. The purpose of this page is to develop a good understanding of how photometric data measurements of brightness are used to construct a light curve.

Use the light curve simulator in following the discussion below. There are four distinct sub-panels visible. The panel in the upper right depicts the eclipsing binary system. Click the Start Animating button to set the system in motion.

The orbital period being simulated here is 3. The periods of most binary systems that have been observed are known to a much higher degree of accuracy.

If one were to look up an eclipsing binary period in the General Catalogue of Variable Stars ā€” it would likely be known to a high degree of accuracy ā€” 3. The periods of many eclipsing binary systems have remained constant for long periods of time over many orbital cycles. The panel in the upper left shows the actual variation in brightness of the system. Note that these two upper windows are synchronized. The red dotted line labeled now indicates the present value of light curve brightness manifested by the binary system.

The pattern of brightness values created by the binary system repeats itself over and over again. The panel in the lower right shows how phase is calculated. If one takes the total elapsed time since some arbitrary starting time and divides by the orbital period, one obtains a real number. The part to the left of the decimal tells you how many complete orbital cycles have passed since the starting time. If you watch the binary system progress over time you can watch this number of cycles slowly increment.

The digits to the right of the decimal point indicate phase. This is a decimal between 0. Note that phase is the x-axis in a light curve. When astronomers begin observing a binary system and taking photometric measurements, they ultimately want to determine the light curve of the system. However, they typically are not able to follow a binary through a complete cycle. Due to the object's availability, observing other objects, and the weather it often takes observations from many cycles to form a light curve as shown in the animation below.

However, until they know the orbital period of the system they can't determine the phase of a data point. A discussion of the method by which periods are determined must wait for another NAAP module and from here on we will assume that the period is known.

Modules List Version 2 Beta Resources. Questions Simulations Images Tables Outlines. Moon Pictures Virtual Astronomy Laboratories. Lightcurves of Eclipsing Binary Systems The variation in brightness of an eclipsing binary is described by its light curve.

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EB Working Group Charter. Eclipsing binary stars are the cornerstone of stellar astrophysics: 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.

Pā€”Lā€”R relationships , promoted eclipsing binaries as calibrators of stellar properties. 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 , determine accurate distances Guinan et al.

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. To support the core Kepler mission, the Eclipsing Binary Working Group assumes the following tasks, in order of priority: 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. This is conducted towards two primary goals: 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: 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.

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: All co-authors must send in a statement that: Co-authorship based on merit to the mission i. 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: 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. The Steering Committee is tasked to overview the projects, goals, progress and effort towards achieving the core tasks. The Committee reviews membership applications and has authoritative power in case of disputes or violations of the rules of conduct. The Kepler Exoplanet Council provides scientific input to the Kepler project. The role of the Representative is to serve as the point of contact within the Kepler project: 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: 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.

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.

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. 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. Violation of the standards for professional behavior will result in dismissal from the EBWG.