Properties of GX Gem After learning the absolute properties of the binary system, the obtained...
1
Properties of GX Gem After learning the absolute properties of the binary system, the obtained values were then used to determine the age and chemical composition of the two stars by interpolation in tables from the Claret and Gimenez evolutionary model. Both the properties and ages of the stars can be found in Figure 4. The X value, or Hydrogen content, was found to be 0.6490, the Y value or Helium content, was 0.321, and the Z value, amount of heavier elements, was 0.0300. While GX Gem’s information can neither prove or disprove current theories of stellar evolution, it can lend credit to one side. Through the remainder of the summer, I hope to explore its bias to one theory or another as well as organizing my findings into a potential publication. GX Gem is a variable star located within the constellation Gemini. Comprised of two stars orbiting each other nearly edge-on from an observer’s viewpoint, the object’s variability results from the stars eclipsing each other and blocking some of the light. GX Gem belongs to a category of binary stars called close binaries since the two stars cannot be individually resolved in a telescope. By studying the variation in light in images taken from November 2001 to April 2006, the properties of the stars as well as of the orbit have been obtained. These values were then used to approximate the age and chemical composition of the stars. By comparing these results with current theories of stellar evolution, I wish to examine whether the stars behave as predicted or, like some other stars, call for a new model of stellar evolution. I would like to thank: •Claud H. Lacy. University of Arkansas. Fayetteville, AR. (Mentor) •Guillermo Torres. Harvard- Smithsonian Center for Astrophysics. Cambridge, MA. (Contributed preliminary radial velocity measurements). •Images of GX Gem were measured by using the Multi-Measure application, including flat field and sky corrections, to measure the magnitudes of variable, comparison, and check stars as displayed in Figure 1. The results were plotted in both a dates plot and phase plot to find whether each eclipse was a primary or secondary. •Reliable dates of minima were obtained from measurements found with Multi-Minima 2.2 and from external papers, then used with the Dates of Minima application to estimate the orbital period accurately, and to learn that the orbit is probably circular. •The orbital ephemeris was determined as HJD Min I = n P + E o with HJD Min I being the Julian date of the primary eclipse, n being the cycle number, P being the period, and E o being an accurate date of primary eclipse, then this ephemeris was used to •A light curve fitter (EBOPP) was used to process the light curve data from Multi-Minima 2.2 to find the central surface brightness of each star, spherical radii, radii ratio, inclination, phase correction, and magnitude outside eclipse, and model the light curve as seen in Figure 2 (solid curve). •Period and ephemeris data were combined with radial velocity data in order to learn, using GLSPL, the binary system radial velocity and semi-amplitudes , resulting in the radial velocity plot shown in Figure 3. •The secondary surface brightness and color index were used to estimate the effective temperatures of the stars (Popper 1980). •Photometric and spectroscopic orbital parameters were used to determine the absolute properties of the stars: masses, radii, Log g, Log L, absolute magnitudes, and synchronous rotational velocities. •Absolute and apparent magnitudes were used to find the distance modulus. Laura Handzel, REU Laura Handzel, REU Student Student Variab le Comparison Check What is GX Gem? What is GX Gem? Finding Finding Eclipses Eclipses Determining Determining Properties Properties Making Making Conclusions Conclusions Acknowledgement Acknowledgement s s GX Gem AbsoluteProperties Primary Uncertainty Secondary Uncertainty M ass(Solar Units) 1.506 0.02 1.495 0.017 Radius(Solar Units) 2.271 0.05 2.237 0.05 LogG (CGS Units) 3.903 0.019 3.913 0.019 LogL (Solar Units) 0.823 0.023 0.802 0.023 AbsoluteM agnitude 2.65 0.05 2.72 0.06 Syn. Rot. Vel. (km/s) 28.2 0.6 27.8 0.6 Temperature(K) 6150 50 6120 50 SurfaceBrightness 3.782 0.001 3.779 0.00275 Age(Billionyrs) 2.376 0.067 2.376 0.067 Eccentricity=0 Inclination=85.8843º+-0.0878 Period=4.037934+-0.000006days Figure 1: CCD image of the variable star GX Gem as Figure 1: CCD image of the variable star GX Gem as well as a comparison and check star of constant well as a comparison and check star of constant brightness with which to compare the variable. brightness with which to compare the variable. Figure 2: Orbital phase diagram with primary Figure 2: Orbital phase diagram with primary mid-eclipse set at 0 phase while mid-secondary mid-eclipse set at 0 phase while mid-secondary eclipse is at 0.5 phase. eclipse is at 0.5 phase. Figure 4: Absolute properties of GX Gem found using Multi- Figure 4: Absolute properties of GX Gem found using Multi- Minima and Terminal. Syn. Rot. Vel. stands for Minima and Terminal. Syn. Rot. Vel. stands for Synchronous Rotational Velocity. Eccentricity, Synchronous Rotational Velocity. Eccentricity, inclination, and period are for the binary system while inclination, and period are for the binary system while the other values are for the individual stars. the other values are for the individual stars. Figure 3: Radial velocity plot; black dots Figure 3: Radial velocity plot; black dots represent measured velocities of primary while represent measured velocities of primary while white dots show velocities of secondary. white dots show velocities of secondary. QuickTime™ and a TIFF (Uncompressed) decompresso are needed to see this pictur QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
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Transcript of Properties of GX Gem After learning the absolute properties of the binary system, the obtained...
Properties of GX Gem
Properties of GX Gem
After learning the absolute properties of the binary system, the obtained values were then used to determine the age and chemical composition of the two stars by interpolation in tables from the Claret and Gimenez evolutionary model. Both the properties and ages of the stars can be found in Figure 4. The X value, or Hydrogen content, was found to be 0.6490, the Y value or Helium content, was 0.321, and the Z value, amount of heavier elements, was 0.0300. While GX Gem’s information can neither prove or disprove current theories of stellar evolution, it can lend credit to one side. Through the remainder of the summer, I hope to explore its bias to one theory or another as well as organizing my findings into a potential publication.
GX Gem is a variable star located within the constellation Gemini. Comprised of two stars orbiting each other nearly edge-on from an observer’s viewpoint, the object’s variability results from the stars eclipsing each other and blocking some of the light. GX Gem belongs to a category of binary stars called close binaries since the two stars cannot be individually resolved in a telescope. By studying the variation in light in images taken from November 2001 to April 2006, the properties of the stars as well as of the orbit have been obtained. These values were then used to approximate the age and chemical composition of the stars. By comparing these results with current theories of stellar evolution, I wish to examine whether the stars behave as predicted or, like some other stars, call for a new model of stellar evolution.
I would like to thank:
•Claud H. Lacy. University of Arkansas. Fayetteville, AR. (Mentor)
•Guillermo Torres. Harvard-Smithsonian Center for Astrophysics. Cambridge, MA. (Contributed preliminary radial velocity measurements).
•Images of GX Gem were measured by using the Multi-Measure application, including flat field and sky corrections, to measure the magnitudes of variable, comparison, and check stars as displayed in Figure 1. The results were plotted in both a dates plot and phase plot to find whether each eclipse was a primary or secondary.
•Reliable dates of minima were obtained from measurements found with Multi-Minima 2.2 and from external papers, then used with the Dates of Minima application to estimate the orbital period accurately, and to learn that the orbit is probably circular.
•The orbital ephemeris was determined as HJD Min I = n P + Eo with HJD Min I being the Julian date of the primary eclipse, n being the cycle number, P being the period, and Eo being an accurate date of primary eclipse, then this ephemeris was used to refine orbital phases with the Multi-Minima 2.2 application.
•A light curve fitter (EBOPP) was used to process the light curve data from Multi-Minima 2.2 to find the central surface brightness of each star, spherical radii, radii ratio, inclination, phase correction, and magnitude outside eclipse, and model the light curve as seen in Figure 2 (solid curve).
•Period and ephemeris data were combined with radial velocity data in order to learn, using GLSPL, the binary system radial velocity and semi-amplitudes , resulting in the radial velocity plot shown in Figure 3.
•The secondary surface brightness and color index were used to estimate the effective temperatures of the stars (Popper 1980).
•Photometric and spectroscopic orbital parameters were used to determine the absolute properties of the stars: masses, radii, Log g, Log L, absolute magnitudes, and synchronous rotational velocities.
•Absolute and apparent magnitudes were used to find the distance modulus.
Laura Handzel, REU Laura Handzel, REU StudentStudent
Variable
Comparison Check
What is GX Gem?What is GX Gem?
Finding Finding EclipsesEclipses
Determining Determining PropertiesProperties
Making Making ConclusionsConclusions
AcknowledgementAcknowledgementss
GX Gem Absolute Properties PrimaryUncertainty SecondaryUncertainty
Mass (Solar Units) 1.506 0.02 1.495 0.017Radius (Solar Units) 2.271 0.05 2.237 0.05LogG (CGS Units) 3.903 0.019 3.913 0.019LogL (Solar Units) 0.823 0.023 0.802 0.023Absolute Magnitude 2.65 0.05 2.72 0.06Syn. Rot. Vel. (km/s) 28.2 0.6 27.8 0.6Temperature (K) 6150 50 6120 50Surface Brightness 3.782 0.001 3.779 0.00275Age (Billion yrs) 2.376 0.067 2.376 0.067 Eccentricity=0 Inclination=85.8843º+-0.0878
Period=4.037934+-0.000006 days
Figure 1: CCD image of the variable star GX Gem as Figure 1: CCD image of the variable star GX Gem as well as a comparison and check star of constant well as a comparison and check star of constant brightness with which to compare the variable.brightness with which to compare the variable.
Figure 2: Orbital phase diagram with primary Figure 2: Orbital phase diagram with primary mid-eclipse set at 0 phase while mid-secondary mid-eclipse set at 0 phase while mid-secondary eclipse is at 0.5 phase.eclipse is at 0.5 phase.
Figure 4: Absolute properties of GX Gem found using Multi-Figure 4: Absolute properties of GX Gem found using Multi-Minima and Terminal. Syn. Rot. Vel. stands for Minima and Terminal. Syn. Rot. Vel. stands for Synchronous Rotational Velocity. Eccentricity, Synchronous Rotational Velocity. Eccentricity, inclination, and period are for the binary system while inclination, and period are for the binary system while the other values are for the individual stars.the other values are for the individual stars.
Figure 3: Radial velocity plot; black dots Figure 3: Radial velocity plot; black dots represent measured velocities of primary while represent measured velocities of primary while white dots show velocities of secondary.white dots show velocities of secondary.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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