1. Binarity among objects with the Be and B[e] phenomena
Anatoly Miroshnichenko
Dept. of Physics & Astronomy, University of North Carolina at Greensboro, USA
Pulkovo Observatory, Saint-Petersburg, Russia
Fesenkov Astrophysical Institute, Almaty, Kazakhstan
S. Zharikov (Inst. Astronomy, Univ. Nacional Autónoma de México)
N. Manset (CFHT Corp., HI, USA)
D. Korčáková (Charles University, Czech Republic)
S. Danford (University of North Carolina at Greensboro, USA)
A. Raj (Indian Institute of Astrophysics, Bangalore, India)
O. Zakhozhay (Main Astron. Observatory, Ukranian Academy of Sciences)

2. Outline Be and B[e] Phenomena Basis for the Binary Hypothesis
Examples of Be and B[e] Binary Systems
Current State of the Problem
Observational Program at the Three College Observatory (TCO) of the University of North Carolina at Greensboro
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3. Be and B[e] Phenomena
Common: B-type dwarfs/giants (Teff = 9000 – K) + emission lines and IR excess
Feature Be
B[e]
Emission lines
Permitted transitions
HI, FeII – all except coolest
He I, Si II, OI – Sp.T.B0–B2
HeII – Sp.T. B0
Both permitted and forbidden transitions
[OI], [FeII], [NII], [SII], NaI
[OIII] – Sp.T. B0–B2
IR excess
free-free + free-bound gas emission
gas +dust
Rotation
close to critical velocity
slower than Be’s

4. Be Stars/The Be Phenomenon
Line emission was discovered in 1866 by A. Secchi
Temperature and gravity at poles are higher than at the equator

5. Reasons for the Be Phenomenon
Rapid rotation: intrinsic (from birth) or induced (mass-transfer in a binary system – Křiž & Harmanec 1975)
Star may speed up on its own due to transfer of momentum from its core to the surface
Mass loss (disk formation): triggered by non-radial pulsations or by close passages in binaries
Disk material orbits the star and moves outward by viscosity but can also fall back onto the star
If mass loss from the star exceeds mass loss from the disk, the material is accumulated near the star

6. Discovery − Allen & Swings(1976, A&A, 47, 293)
The B[e] Phenomenon
Discovery − Allen & Swings(1976, A&A, 47, 293)
65 B-type stars (out of 700) with forbidden line emission ([Fe II], [O I], [O III]) and IR excess at =2 m
5 groups of B[e] stars: supergiant B[e], pre-main-sequence B[e], compact Planetary Nebulae B[e], symbiotic B[e], and unclassified B[e] – Lamers et al. (1998, A&A, 340, 117)
32 unclassified B[e] – no reliable distances OR mixture of features from different groups. Most of them became FS CMa objects + ~50 newly found
The group of FS CMa objects (Miroshnichenko 2007, ApJ, 667, 497) has NOT replaced the “Unclassified B[e]” group but rather rejected some explanations about the objects’ nature.
Only B[e]sg and FS CMa objects seem to create dust due to binary interaction, the other groups have dust created earlier

7. Be vs. B[e]
Be stars lose and replenish circumprimary disks on time scales of years (randomly).
B[e] stars have never been reported to get rid of the disk.
There are hundreds of Be stars with 1 kpc from the Sun.
Only a few B[e] objects have been found in this region (easy to discover due to a strong IR excess).
Both, Be and B[e], typically have secondary components, which are much fainter than the B-star (ΔV ≥ 2 mag).
Orbital periods: Be – from ~1 week to ~1 year
B[e] – 19.4, 27.5, 31.0, days

8. Be vs. B[e] Brightness distribution
Be stars occupy the entire region of the Main Sequence
Miroshnichenko (2008, ASP Conf. Ser., 388, 205)

9. Binary Statistics Be B[e]
Pavlovski et al. (1997, A&AS, 125, 75) : 16 sp. binaries
Gies (2000, ASP Conf. Ser, 214, 668) : 40 objects (13 unconfirmed)
Harmanec (2001, Bull.Astron.Inst.Czech., 89, 9):165 objects (19 Be)
Current: 14 binaries out of 24 stars brighter than 4m
Current: 75 binaries out of 237 stars brighter than 7.5m
B[e]
Subgroup
Allen & Swings(1976)
Current
Binaries
HAeB[e] 6
~100
<50
sgB[e] 7
~15
~10
cPNB[e] 13
>100
~30
symB[e]
all
unclB[e]
32 (23 FS CMa + 9 uncl)
~70 FS CMa + 7 uncl
~20

10. Be Star Phases (π Aqr) Diskless Active
Bjorkman, Miroshnichenko, et al. 2002, ApJ, 573, 812

11.  Aquarii Density structure of the disk Plus sign − the center of mass
V/R variations of the Hα line for ~40 orbits/~10 years (Zharikov et al. 2013, A&A, 560, A30)
Density structure of the disk
Plus sign − the center of mass
Near maximum of the active phase
Near the end of the active phase

12. ν Gem Mass function f(m) = 0.12 M Parameter Rivinius+ (2006) TCO
Period, d
53.73±0.02
53.76±0.03
RV, semiA
km/s
38±8
27.4±2.7 e
0.11±0.05

13. 48 Librae
V ~ 4.8−4.95 mag, B4 IIIe, V sin i ~ 400 km/s

14. Be Stars with Disks in Transition
φ And, 66 Oph, λ Eri – very weak Hα emission
θ CrB – a new disk formation?

15. Properties of FS CMa objects
Comparison of a hot (B1) and a cool (A1) FS CMa object.
Hα line profiles of some FS CMa objects.

16. FS CMa Objects: IR excess
Coolest (A-type) stars
B3−B5 stars
Spitzer Space Observatory data – proof of dust (Miroshnichenko et al. (2011, IAU Symposium 272, p.412)

17. The B[e] Binary MWC 728
MWC 728 (B5Ve+G8 III) Miroshnichenko+ 2015, ApJ, 809, 129
Orb. period 27.5 days, RV semi-amplitude 20 km/s
Distance ~1 kpc, angular separation ~20-30 mas
A flat continuum was added to the spectrum of the Li-rich giant HD to match the line strengths of MWC 728

18. CI Cam Vr amplitude ~230 km/s Orbital period = 19.4 days
Secondary is a compact object

19. A Unique Object: FBS0022021 b = −64o ! V = 15 mag V−K= 4 mag
AV= 0.2 mag
SpT B5 from the optical continuum slope (Zharikov et al. 2004), Too faint for IRAS
If main-sequence luminosity  distance 7.5 kpc!
No HeI lines detected
Was suggested to be a U Gem-type CV, but no brightness variations detected for the last 15 years

20. HD – a 6.6-mag FS CMa Object
Possible periodicity on a timescale of 10−15 years
Further monitoring is important

21. A Binary B[e] Object Sketch

22. Conclusions A large fraction of Be stars can be binary systems
It is already >50% for the brightest Be’s
Analysis of the available ProAm data (e.g., BeSS database) needs to be done to search for fainter binaries
Be’s with always weak-line emission may be single
Most if not all B[e] stars should be binaries (mergers may exist as well – no proof yet)
Spectroscopic monitoring of relatively faint objects (V ~ mag) is strongly needed to search for binaries
Be and B[e] phenomena may represent subsequent evolutionary stages of certain intermediate-mass binaries

23. Three College Observatory (TCO)
Operated by the University of North Carolina at Greensboro
Location: latitude +35°56’, longitude 79°24’ West
Telescope: 0.81-m Cassegrain, F/13.6, installed in 1981
Equipment: échelle-spectrograph, Shelyak Instr., France, CCD: SBIG ST7XMEI (2011−2013) , ATIK−460EX (from 2013)

24. TCO Telescope & Echelle Spectrograph
Shelyak Instr.: Fibers (F/5): 50-m object (10-meter long) and a 200-m calibration
Spectral coverage: 31 orders, 3800 − 7900 Ǻ
Resolving power: λ/Δλ ~ 12,000
Threshold: V ~ 10 mag; 6-mag star S/N~100 for 30 min

25. TCO Observing Program
Types of object being observed: Be stars, objects with the B[e] Phenomenon, early-type dwarfs and supergiants, binary systems, horizontal branch stars, pre-main sequence Herbig Ae/Be stars, radial velocity standards.
Statistics: 542 nights in 7.5 years, over 4000 spectra of over 400 objects.
Be stars: ψ Per (224 spectra), β CMi (218), ν Gem (151), EW Lac (137), β Psc (28), 10 Cas (40), γ Cas (29), φ And (91), BK Cam (12), Pleione (33), 105 Tau (16), ζ Tau (19), HD (34), κ Dra (43), θ CrB (12), 48 Lib (38), δ Sco (61), χ Oph (33), 66 Oph (37), ε Cap (20), π Aqr (84), V777 Cas (6), 48 Per (21)

26.  Sco B0 IV + B3: V:
Binarity discovered in 1901 through lunar occultation
Secondary resolved by interferometry in the 1970s
Primary component was used as a spectral classification standard throughout the 20th century.
Secondary is ~1.5 mag fainter
Orbital eccentricity e = 0.94±0.01
Showed temporary Hα line emission in the 1990s
Started developing a steady disk in the summer of 2000
V = 2.32 mag in the 20th century with no disk
V = 1.6 – 2.2 mag in the 21st century with the disk
Component separation from 6 to 200 mas

27. δ Sco at periastron of 2011
Part of the spectrum at a resolution of ~ taken at the 3.6-meter Canada-France-Hawaii Telescope
Radial velocity curve for the He II 4686 Å line near periastron time. Solid line – orbit 2000
Dashed line – orbit 2011
From Miroshnichenko et al. (2013, ApJ, 766, 119)
Pro-Am campaign including 10 clear night at a 0.8-m telescope on Tenerife

28. δ Sco at R ~ 12000 Spectra taken at the 0.81-meter TCO telescope
Eshel (from Shelyak Instr.) + ATIK460EX
Star altitude angle ~ 20° − 30° above the horizon

29. δ Sco – Next Periastron Orbital period : 10.8092 ± 0.0005 years
: ± 1.8 days
Next periastron: 2022 April 22 – 26
: JD ± 1.8
Can be observed between late January and late September
A new campaign from the Spring of 2021 till Fall of 2022
Goals (at least):
Monitor spectral line variations in profiles and radial velocity (most important – Hα and He II 4686 Å)
Search for signatures of the secondary

30. Conference announcement
“Hot Stars: Life with Circumstellar Matter”
Almaty, Kazakhstan, July 19-24, 2020
Main focus on hot stars with circumstellar material, which shows up as spectral line emission, excess radiation in the visual and infrared regions, stellar spectrum veiling, nebulocities, brightness and spectrum variations.
Classes of object: pre-main-sequence Herbig Ae/Be stars, Be stars, objects with the B[e] phenomenon, hot supergiants, Wolf-Rayet stars, Luminous Blue Variables, and planetary nebulae.
Website:

31. Scientific Organizing Committee
Marcelo Borges Fernandes (Brazil)
Alex Carciofi (Brazil)
Daniela Korcakova (Czech Republic)
Michaela Kraus (Czech Republic)
Alex Lobel (Belgium)
Ronald Mennickent (Chile)
Anatoly Miroshnichenko, Chair (USA)
Rene Oudmaijer (UK)
Jorick Vink (UK)
Zeinulla Zhanabaev (Kazakhstan)
Sergei Zharikov (Mexico)

32. Former Capital of Kazakhstan
City of Almaty
Former Capital of Kazakhstan

33. Al-Farabi Kazakh National University

34. Tien-Shan Astronomical Observatory
elevation 2800 m
Two 1-meter Carl Zeiss telescope, built 1988

35. Assy – Turgen Astronomical Observatory
elevation 2700 meters
1-meter Carl Zeiss telescope (1980)

36. Assy – Turgen Astronomical Observatory
elevation 2700 meters
1.5-meter telescope (assembled 1992, first light 2017)