Search for Close Binaries of Herbig Ae/Be Stars

1. Search for Close Binaries of Herbig Ae/Be Stars Maria Jose Cordero, Sandrine Thomas, Nicole van der Bliek, Greg Doppman, Bernadette Rodgers, Anne Sweet CTIO PIA PROGRAM

2. Pre-MS stars with masses between 2-8 • Spectral types ranging from B to F • Emission lines and NIR excess associated to a circumstellar disk Characteristics HAEBE stars Why study HAEBE stars? To understand the star formation as function of the mass

3. Observations indicates that HAEBE stars: • They have been found in large associations, small clusters or isolated stars (Testi et al 1997) • Shown binary fraction greater than T Tauri stars (Bouvier et al 2001) • Had companions between 3-5 magnitudes fainter than the primary star (Testi et al 1997) • Correlation between clustering and spectral type (Testi et al 1997) • HAEBE stars are in between high mass and low mass formation mode Small samples (~ 20)  need bigger sample (150)

4. How does it restrict the formation model? • Stellar density as function of the mass • Companions properties • Binary mass ratio (indirectly) • GOAL: Search for close binaries of HAEBE stars • Separation, position angle, magnitudes differences, detection limit.

5. Difficulties? • The angular separation decreases as the distance increases • Faint companions: 3 to 5 magnitudes fainter Using AO it is possible to detect closer, fainter objects

6. Feedback AO system Distorted wavefront Corrected wavefront Imager DM WFS

7. NIRI/Altair • With this configuration it would be possible to detect companions as close as 0.1” and about 5 mag. fainter in the best conditions. • The images were taken the last semester in queue mode using: • 100 images with short exposure time (0.5-3 s) • 4 Dithering • K or BrGamma filter

8. 4 Dithering Each dithering contains 100 images with a short exposure time (1-3 s)

9. My work: IR data reduction • To remove sky background from each image • To subtract Flat Field Off from Flat Field On • To shift the images and add all 4 images

10. Result data reduction: example Before reduction After reduction 1 image All 4 images

11. Fitting the PSF Once the images are reduced, the PSF must be obtain: • To make concentric aperture photometry on primary star • To create the PSF of the primary star • To apply the PSF on the possible companions HD235495 ρ = 2.084 " K = 4.712 PA = 297 ° HK Ori ρ = 0.349 " K = 1.647 PA = 40.9 °

12. Detection Limit 5 HBC 217 ρ > 0.087 " K < 9.7 Companion: If K ~ 5 then ρ > 0.3 " 0 K -5 -10 -15 0.01 0.10 1.00 10.00 Separation in arcsec

13. Detection Limit 5 HBC 531 0 ρ > 0.087 " K < 8.48 Companion: If K ~ 5 then ρ > 0.3 " K -5 -10 -15 0.01 0.10 1.00 10.00 Separation in arcsec

14. Binaries systems 22 binary candidates were found out of 42 B = 10 A = 3 F = 1 G = 3 UNK = 5

15. Future work • Photometry (SEDs) • Spectroscopy to the companions • Increases the sample to do meaningful statistical analysis

16. Conclusions • I reduced 42 stars and I found 22 stars with companions • The detection limit that was obtained is: • ρ > 0.087 ’’ for small K • K < 9.7 for larger ρ • If K = 5, then ρ > 0.3 ’’ • Preliminary histogram frecuency of binary v/s spectral type

17. Gracias….. • A CTIO por hacer posible esta investigacion • A Nicole y Sandrine por su paciencia y por mostrarme todo lo que aprendi • A Stella por preocuparse de nosotros • A Petri por responder mis estupidas dudas con Linux • Al team REU y PIA: chiquillos ustedes son los mejores!!!!