Study of Planet forming Systems Orbiting Intermediate-mass Stars Sweta Shah Ithaca College Advisor: Dr. Luke Keller In collaboration with the NASA Spitzer Space Telescope InfraRed Spectrograph Disk’s Team Image credit: Caltech

Theory of Planet formation Adapted from Hogerheide 1998

Why intermediate mass (Herbig Ae Be) stars ? Hot and massive 12, ,000 K 2-10 solar mass Excess thermal (IR) radiation ‘e’ Emission line spectra Circumstellar disks in Orion Nebula (Hubble Space Telescope Image: McCaughrean & O’Dell 1995)

Spectral characteristics of the Accretion Disk Thermal IR excess PAH Dust -silicates Spectral Energy Distribution (Malfait et al. 1998) UV mm

Correlation of SED and disk geometry (Malfait et al. 1998)

Physical structure of the disks: SEDs (UV-mm) IRS SL IRS SL IRS SL IRS SL LL (Malfait et al. 1998)

Spectral features - PAH? Polycyclic Aromatic Hydrocarbon Excited by UV radiation H H H H H H H H H H H H Sloan, Keller, Leibensperger et al very stable

What is the shape of the disk? How do we test this hypothesis?

Measuring the strength of “bumps” in Infrared continuum

Star with no disk Flared disks Flat disks Dust grain growth and settling Keller, Shah et al. 2006, paper in preparation Increasing 6-13  m SED slope Increasing  m SED slope

Ultimate Goal Disk evolution in time I PAH ?!

Thanks! (Any ?)

Spitzer InfraRed Telescope Facility –Background-limited sensitivity 3 – 180  m –85 cm f/12 beryllium R-C telescope, T < 5.5K –Three scientific instruments provide: Imaging/photometry,  m Spectroscopy, 5-40  m (R = 90 & 600) Spectrophotometry,  m –5.5 yr lifetime –Launched on 25 August 2003 –Birth stone: forsterite IRS