A Study of Accretion Disks Around Young Binary Star Systems Paula Johns, Northern Arizona University Mentor: Lisa Prato, Lowell Observatory http://www.shatters.net

Why is the Study of Accretion Disks Important? Can determine parameters such as efective temperatures, spectral types, luminosities, And masses, as well as accretion properties and near-infrared excesses for the individual binary components. Contain the material for the formation of planetary systems. Is evolution different than for single star systems? http://www.universetoday.com

What are T Tauri Stars? Characterized by… Vigorous activity Strong stellar winds Variable and irregular light curves Found in nebulous regions < 2 solar masses < 10 million years old Newly formed low-mass stars that have recently become visible in the optical range Pre main sequence First one percent

Data Collection University of Hawaii 88” 800 spectral resolution in K-band Low resolution infrared spectroscopy and photometry Talk about moving telescope to center on object, grating changes wavelengths received, talk about how system works Kspec=name of spectrograph http://www.ifa.hawaii.edu

Aspects to Take into Consideration… Extinction ~ Reddening attributable to dust Infrared Excess~ Infrared flux in excess of that expected by assuming star is a black body Veiling~ Filling in of spectral absorption lines by an IR excess Rk=veiling, star is not perfect black body as a result of the dust in disk Extinction=dust absorbs/scatters more frequently at shorter wavelengths http://www.ok4me2.net

Spectra result from a combination of the young star photosphere and excess IR radiation from circumstellar disk material and IR emission from accretion processes and interstellar extinction along the line of sight

Spectral Standards Hotter Cooler Create a model spectra of the underlying young star photosphere, beginning with an observed young star spectrum and varying the parameters of extinction amplitude of the k band excess and in some cases the slope of the excess Water lines “eat” away at line on right side causing curve Av affects shape of line, increase in extinction increases slope Cooler

Br gamma line (Hydrogen) emission indicates that objects have active accreting circumstellar disks Larger Rk(veiling) make spectra flatter Mention that physically separated to see difference

LK Ca 7 Secondary K5 M5 Top is K5, av= 9.2, cc=.66, rk=0 Bottom is M5, av=0, cc=1.62, rk=0 Black line is Lk Ca 7 Least squares fit / X fit

LK Ca 7 Secondary Averaged K5 and M5 Lk Ca 7 2* M5,K5 spectral type Av=0, rk=0, ratio=.24 Ang sep 0.25” fcn of telescope, .22wavelength/D

Results Determined the spectral types of stars in 11 systems by comparing them to spectral standards Determined extinction and K band excess No significant correlation has been found between stellar spectral type and the K band excess, implying that the mass of a star is independent of the size or presence of a circumstellar disk Future work: Mass and age of stars will be determined by comparing fit to H-R diagram Luminosities, and effective temperature?

Acknowledgments N.A.S.A. Space Grant Consortium Lowell Observatory Northern Arizona University Tom Greene

Thank You