Spectra of the Brightest Be stars and Objects Description

1. Spectra of the Brightest Be stars and Objects Description Anatoly Miroshnichenko University of North Carolina at Greensboro USA • Observational Features of Be Stars • Temporal Behavior of Individual Objects • Bright Objects for Monitoring

2.  Cassiopeae discovered in 1866 Be Stars Circumstellar gas has a flattened distribution (disk-like) • Main Properties: • Intermediate luminosity • Emission-line spectra • Rapid rotation

3. What Is Unknown? • How and why the disks evolve? • Disks seem to disappear completely • Mass loss rate seems to be variable • Are Be stars single objects or binary systems? • 25% detected binaries in the brightest 240 Be stars • Weak-lined objects can be single or close binaries • Strong-lined objects can be wide binaries

4. 9 non-overlapping orders, 70 Å each, range 52856600 Å. Includes spectral lines of FeII 5317 & 6383, HeI 5876, NaI 5889 & 5895, SiII 6347 & 6371, and H Spectral resolving power R (/) ~ 26000 Spectroscopy of Be Stars at the Ritter Observatory • 1-meter telescope with a fiberfed echelle spectrograph and a 1150x1150-pixel CCD in the Coude focus • Spectra of stars brighter than 7.5 mag can be obtained in 1 hour with a signal-to-noise ratio of ~100 • ~2000 spectra of ~ 45 Be stars obtained in 19912007

5.  Cassiopeae

6.  Cassiopeae

7. 48 Librae V ~ 4.84.95 mag B4 IIIe D=15717 pc V sin i ~ 400 km/s

8. 48 Librae

9.  Canis Minoris V ~ 2.9 mag B8 Ve D=522 pc V sin i ~ 245 km/s Possible orbital periods: 218.5 days and 3 years Both not confirmed

10.  Canis Minoris

11.  Canis Minoris

12.  Canis Minoris

13.  Persei V ~ 4.2 mag B5 Ve D=21530 pc V sin i ~ 212 km/s

14.  Persei

15. 66 Oph V ~ 4.6 mag B2 Ve D=20740 pc V sin i ~ 240 km/s

16. 66 Oph

17.  Cassiopeae V ~ 4.5 mag B5 IIIe D=28080 pc V sin i ~ 220 km/s No line emission in 1970-s

18.  Cassiopeae

19. Orbital period vs. EW (H) • Conclusions: • Longer orbital period  larger disk  stronger lines • Later spectral type  smaller ionized disk area  weaker lines + - Be/X-ray binaries • - B1 4 Be binaries ° - B5  8 Be binaries

20. What We Get Studying Binaries Most Be binaries are single-lined  secondaries are much fainter than primaries The brightness difference is V ~ 24 magnitudes Orbital periods and spectroscopic masses  companion separation  disk sizes The main disk responsible for the line emission and IR excess is around the primary companion The secondary may have some amount of circumstellar matter around it

21.  Aquarii UB V K BV Polarization EW (H)

22.  Aquarii

23.  Aquarii

24. Be Binary Candidates

25. How and What to Look For • Regular low-resolution spectral observations: • search for dramatic variations (new disk formation or disappearance) • monitoring of long-term changes of the line strength Goals of higher-resolution spectroscopy

26. Galactic Be Stars The only catalog of Galactic Be stars – Jaschek & Egret (1982) It contains 1159 objects down to ~13 mag About 30% of them may not be Be stars (we only know that they have H emission) The brightest part of the catalog has been cleaned: there are ~310 Be stars brighter than ~7.5 mag Fainter ones need to be observed spectroscopically and reclassfied

27. Summary • Monitoring of bright Be star is important for finding the reasons for the phenomenon • Spectral resolution of 500020000 can be enough to search for condition changes in the disk and searching for orbital motion • Frequency of observations: twice a month when the changes are slow and as frequent as possible when rapid changes occur • Observations of objects fainter than ~7 mag are important to clean up the existing catalog of Galactic Be stars