1. Spectral Monitoring of UXORs with Interference Filters V. Strelnitski, L. Weiss, M. Davidson, & G. Walker Maria Mitchell Association AAVSO Meeting, 10-17-08 V3798 Sgr

2. UXORs Herbig AeBe stars Herbig AeBe stars Deep irregular drops of brightness Deep irregular drops of brightness Small dust cloudlets [in a disk] ? Small dust cloudlets [in a disk] ?

4. RR Tau: Photometry and Spectroscopy

5. RR Tau, Spectra

6. Line Flux versus Continuum Brightness

7. V3798 Sgr R.A.: 18 15 25.73 DEC: -19 39 15.1 (2000.0)

8. V3798 Sgr H α (6563Å) Ri (6450Å)

9. A drop of theory… Differential Photometry: S (adu) T / (adu) C 1. Emission line flux correlates with the observed continuum flux S(H α ) = βγ * κS(Ri), β [f T (6563) * Δλ T (H α ) / f T (6450) * Δλ T (Ri)] * [f C (6450) * Δλ C (Ri)] ] / [ f C (6563) * Δλ C (H α )] γ 1 – (W a – W e ) / Δλ T (H α ) κ = exp [τ(6450) - τ (6563)] = exp [0.0158 Δm(Ri)]. 2. Emission line flux does not correlate with the dimming due to dust S(H α ) = βγ * κS(Ri) + E / [ f C (6563)]*Δλ(H α )], γ 1 – W a / Δλ T (H α )

10. Period 1 Period 2

11. R CrB

12. Period 1 Period 2 Are UXORs intrinsically variable?

13. S(H α ) versus κS(Ri)

14. V3798 Sgr: Ri and Hα Emission Period 1 Period 2 Period 1 Period 2

15. Conclusions Interference filter photometry of UXORs allows for separation of emission line variability from continuum variability Interference filter photometry of UXORs allows for separation of emission line variability from continuum variability V3798 Sgr is a new UXOR and it may be intrinsically variable V3798 Sgr is a new UXOR and it may be intrinsically variable MMO starts an extensive program of monitoring UXORs with interference filters MMO starts an extensive program of monitoring UXORs with interference filters