Probing the Structure and Dynamics of B[E] Supergiant Stars' Disks

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions

Probing the structure and dynamics of B[e] supergiant stars’ disks

Michaela Kraus

Tartu Observatory

March 16, 2016

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions

1 Introduction

2 The disks of B[e] supergiants

3 Formation mechanism(s) of B[e] supergiant stars’ disks

4 Conclusions

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Follow-up infrared surveys (Allen & Swings 1972; Allen 1973, 1974; Allen & Glass 1974, 1975) reveal two distinct populations of emission-line stars emission-line stars with normal stellar IR colors emission-line stars with IR excess emission due to hot dust Conti (1976) suggested to call these peculiar B-type emission-line stars with forbidden lines and dust as B[e] stars Identiﬁcation of more and more stars with similar properties Deﬁnition of general criteria is needed.

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Introduction - B[e] Stars

Discovery of B[e] Stars Geisel (1970) found infrared (IR) excess emission in a sample of emission-line stars of spectral type B with low-excitation emission lines (especially Fe II and [Fe III]).

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Conti (1976) suggested to call these peculiar B-type emission-line stars with forbidden lines and dust as B[e] stars Identiﬁcation of more and more stars with similar properties Deﬁnition of general criteria is needed.

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Introduction - B[e] Stars

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Identiﬁcation of more and more stars with similar properties Deﬁnition of general criteria is needed.

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Introduction - B[e] Stars

Discovery of B[e] Stars Geisel (1970) found infrared (IR) excess emission in a sample of emission-line stars of spectral type B with low-excitation emission lines (especially Fe II and [Fe III]). Follow-up infrared surveys (Allen & Swings 1972; Allen 1973, 1974; Allen & Glass 1974, 1975) reveal two distinct populations of emission-line stars emission-line stars with normal stellar IR colors emission-line stars with IR excess emission due to hot dust Conti (1976) suggested to call these peculiar B-type emission-line stars with forbidden lines and dust as B[e] stars

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Deﬁnition of general criteria is needed.

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Introduction - B[e] Stars

Deﬁning criteria for B[e] stars strong Balmer emission lines low-excitation permitted emission lines, predominantly of singly ionized metals, in particular of Fe II;

forbidden emission lines of [O I] and [Fe II]; a strong near/mid IR excess due to hot (T 1000 K) circumstellar dust. '

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks ⇓ Characteristics can be found in stars in various evolutionary stages! Classiﬁcation of the stars with the B[e] phenomenon by Lamers et al. (1998)

⇓ ⇓ ⇓ ⇓ pre-MS stars: post-MS stars: post-MS stars: interacting binaries: Herbig B[e] compact PNe B[e] B[e] supergiants symbiotic stars

The remaining 50% could not be classiﬁed and are kept as a separate group of unclassiﬁed∼ B[e] stars.

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Introduction - B[e] Stars

Criteria are mainly based on emission features seen in optical spectra These features represent speciﬁc physical conditions within the circumstellar material, but contain no information on the star itself !

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks ⇓ ⇓ ⇓ ⇓ pre-MS stars: post-MS stars: post-MS stars: interacting binaries: Herbig B[e] compact PNe B[e] B[e] supergiants symbiotic stars

The remaining 50% could not be classiﬁed and are kept as a separate group of unclassiﬁed∼ B[e] stars.

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Introduction - B[e] Stars

⇓ Characteristics can be found in stars in various evolutionary stages! Classiﬁcation of the stars with the B[e] phenomenon by Lamers et al. (1998)

⇓ ⇓ ⇓ ⇓ pre-MS stars: post-MS stars: post-MS stars: interacting binaries: Herbig B[e] compact PNe B[e] B[e] supergiants symbiotic stars

The remaining 50% could not be classiﬁed and are kept as a separate group of unclassiﬁed∼ B[e] stars.

Herbig B[e] cPNe B[e] B[e] supergiant symbiotic B[e] B-type B-type obscured O-type B-type obscured hot spectrum PMS star white dwarf supergiant compact obj. forbidden reﬂection PN nebula high-density associated emission nebula non-spherical nebula lines wind dust and PMS high-density high-density accretion Balmer accretion dusty disk (outﬂowing ?) disk lines disk disk

(d)

V921 Sco-A Hen 2-90 Artist’s view Ant nebula Herbig B[e] cPNe supergiant symbiotic

Additional characteristics of B[e] supergiants: Stars are supergiants, i.e. log L /L 4.0 ∗ ≥ Chemically processed materiel indicating an evolved evolutionary phase Hybrid spectra, i.e. simultaneously narrow low-excitation emission lines and broad absorption features of higher-excitation lines Density contrast between equatorial and polar wind of 100 – 1000

LMC B[e] supergiant R 126 (IUE spectrum) Si IV Si IV

1 Hot stellar wind with v 1800 km s− (Zickgraf et al.∞ 1985)' 1 Lines with FWHM of 20 – 30 km s−

Hybrid wind model suggested by Zickgraf et al. (1985).

Observational evidence for the disk 1. strong infrared excess emission due to hot dust

(from Bonanos et al. 2009)

Observational evidence for the disk 2. high intrinsic polarization due to electron scattering in a wind with density contrast of 1000 between equatorial and polar wind.

τ 0 0.2 0.4 0.6 0.8 64 Cohen et al. 3

a R 66 1. 2. 3. b R 50 h i = 90 O c S 18 d R 126 e S 12 f S 134 g R 82 2 h S 22

i = 60 O 1.Figure No 3. polarization Schematic view of polarization production in various CSE ge- ometries. When the CSE is unresolved, the net polarization observed will be

the co-addition of all polarization produced. Left: A spherical, homogeneous P (%) 2.distribution Perhaps of scatterers polarization will produce zero net polarization. Center: A non- spherical, non-homogeneous, “blobby” distribution of scatterers may produce g i = 45 O a net polarization, but it will depend on the number, spatial distribution, and e relative densities of the blobs. If the blobs are time-variable, the observed 3.polarization Definitely will also be variable.polarization Right: A disk-like distribution of scatterers 1 will produce a net polarization with a position angle perpendicular to the b disk, because there is little or no cancellation due to polar material. d f i = 30 O CSEs are not spatially resolved, the observed signal is the coadded net polarization. As a result, the polarization position angle gives a measurement of the S 111 c orientation of the disk on the sky, even when the disk is not resolved. While the electron scattering polarization is wavelength independent, the ob- a served polarization does show a wavelength dependence. This happens because of the pre- and post-scattering attenuation of polarized light by the disk material (measurementsas the photons work their way through the disk from (Wood & Bjorkman 1995; Wood 0 et al. 1996a,b). When the absorption cross sections are larger, less polarized flux 0 2 4 6 will escape from the disk, and so the net polarization measured will be smaller 2 1/2 9 -3 Melgarejoat those wavelengths. This et effect al. means 2001) that the polarization “spectrum” can (x10 cm ) provide a direct probe of the physical conditions of the disk material, including temperature and density. Thus, the measured intrinsic polarization depends on the disk geometry, density, and temperature (which affects the opacity). As an example, we show an observation of ζ Tau in Fig. 4, along with Monte Carlo model calculations of the percent polarization versus disk opening angle. As this figure shows,M. there Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks is a degeneracy in the opening angle determination. However, when combined with Hα interferometry (Quirrenbach et al. 1997), the large opening angle can be ruled out, and the small opening angle value is determined to be the correct one. The results from the types of studies described above show that Be star disks are surprisingly thin, with typical opening angles of only 2.5 degrees. These opening angles are consistent with disk thicknesses that would be predicted by models of pressure-supported (Keplerian) disks, although the polarization observations do not themselves provide direct evidence that the disks are Keplerian. Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

Observational evidence for the disk 3. detection of molecular emission fromCO (McGregor et al. 1988a,b; 1989; Morris et al. 1996; Oksala et al. 2013) and possibly TiO (Zickgraf et al. 1989; Torres et al. 2012)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks

!"# ! !

v T R

term e

R T

T R R

M yr

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

Observational evidence for the disk ω 4. intense [O I] lines, which fast imply: CAK−type (broad UV lines) polar wind hydrogen is predominantly neutral in the line formation region CO H I α outflowing dust [O I] disk the density of the TiO environment must be high to have sufﬁcient free electrons for collisional excitation of 3000 T[K] < 1500 ~ 7000 (Kraus et al. 2007; 2010) the levels. − 5000

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks The B[e] supergiant puzzle How do B[e] supergiants create circumstellar disks that are dense enough to provide a cool environment for efﬁcient molecule and dust condensation?

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

The dusty disk of CPD-57 2847 resolved by interferometry (VLTI/MIDI, Domiciano de Souza et al. 2011)

Intensity map at 10 µm

The dusty disk of CPD-57 2847 resolved by interferometry (VLTI/MIDI, Domiciano de Souza et al. The B[e] supergiant 2011) puzzle How do B[e] supergiants create circumstellar disks that are dense enough to provide a cool environment for efﬁcient molecule and dust condensation?

Intensity map at 10 µm

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Rapidly rotating stars will have non-spherical winds!

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

Proposed scenarios Rapid stellar rotation: Information on v sin i exists for only 4 objects (Gummersbach et al. 1995; Zickgraf 2000, 2006; Kraus et al. 2010). But all 4 stars rotate at a substantial fraction (> 40%) of their critical velocity !

Rapidly rotating stars will have non-spherical winds!

Wind-compressed disk model of Bjorkman & Cassinelli (1993)

However: Proper inclusion of the non-radial forces due to surface distortion...

...prevents the formation of a disk (Owocki et al. 1996).

Considering rotationally distorted surface: Mass ﬂux, escape velocity, and surface density decrease from pole to equator with increasing rotation velocity

= Stars lose more mass in polar direction ! ⇒ (Maeder & Desjacques 2001)

However: Effective temperature decreases as well !

Fig. 1. E ective temperature distribution on the surface of a rotating Ionization structure calculations reveal recombination close to the stellar surface ! But for a depleted equatorial plane. (Kraus 2006)

Change in Teﬀ with θ causes a change in ionization in the wind This bistability (recombination Fe IV Fe III) occurs around 25 000 K. → Results in a sudden increase in mass ﬂux (Pelupessy et al. 2000)

Fm (M /yr)

However, a density contrast between equator and pole of only 10 is achieved!∼

Slow-wind solution Cure´ (2004) showed that the classical CAK wind solution ceases for Ω > 0.6 and another, slow solution exists. Slow-wind solution in combination with the bistability (Cure´ et al. 2005) is capable to produce high density contrasts in the equatorial wind

10 4

10 3 p Ρ e Ρ 10 2

10 1

10 -2 10 0 10 2 rR* -1 Fig. 4. m-CAK model: density contrastM. Kraus versus Probingr/R the1, structure dashed-line and dynamics is of B[e] supergiant stars’ disks ∗ − for Ω = 0.6 and continuous-line are for Ω = 0.7, 0 .8, 0 .9, 0 .99. The higher is Ω, the higher is the density contrast. BUT: Prevented by the non-radial forces (Owocki et al. 1996) Bi-stability mechanism (Pelupessy et al. 2000) BUT: Does not deliver high enough density contrast Existence of a slow solution in line-driven winds (Cure´ 2004) combined with the bi-stability mechanism produces equatorial density enhancements of the right order (Cure´ et al. 2005)

1 BUT: Terminal velocities of the slow-wind (200 - 300 km s− ) are more than 10 1 times higher than observed (10 - 30 km s− )

⇓ To unveil possible mechanism(s) that form B[e] supergiant stars’ disks, we need to know their structure and kinematics

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

Problems in formation of high-density disks - summarized wind-compressed disk (Bjorkman & Cassinelli, 1993)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Bi-stability mechanism (Pelupessy et al. 2000) BUT: Does not deliver high enough density contrast Existence of a slow solution in line-driven winds (Cure´ 2004) combined with the bi-stability mechanism produces equatorial density enhancements of the right order (Cure´ et al. 2005)

1 BUT: Terminal velocities of the slow-wind (200 - 300 km s− ) are more than 10 1 times higher than observed (10 - 30 km s− )

⇓ To unveil possible mechanism(s) that form B[e] supergiant stars’ disks, we need to know their structure and kinematics

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

Problems in formation of high-density disks - summarized wind-compressed disk (Bjorkman & Cassinelli, 1993) BUT: Prevented by the non-radial forces (Owocki et al. 1996)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks BUT: Does not deliver high enough density contrast Existence of a slow solution in line-driven winds (Cure´ 2004) combined with the bi-stability mechanism produces equatorial density enhancements of the right order (Cure´ et al. 2005)

1 BUT: Terminal velocities of the slow-wind (200 - 300 km s− ) are more than 10 1 times higher than observed (10 - 30 km s− )

⇓ To unveil possible mechanism(s) that form B[e] supergiant stars’ disks, we need to know their structure and kinematics

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Existence of a slow solution in line-driven winds (Cure´ 2004) combined with the bi-stability mechanism produces equatorial density enhancements of the right order (Cure´ et al. 2005)

1 BUT: Terminal velocities of the slow-wind (200 - 300 km s− ) are more than 10 1 times higher than observed (10 - 30 km s− )

⇓ To unveil possible mechanism(s) that form B[e] supergiant stars’ disks, we need to know their structure and kinematics

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks 1 BUT: Terminal velocities of the slow-wind (200 - 300 km s− ) are more than 10 1 times higher than observed (10 - 30 km s− )

⇓ To unveil possible mechanism(s) that form B[e] supergiant stars’ disks, we need to know their structure and kinematics

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

Problems in formation of high-density disks - summarized wind-compressed disk (Bjorkman & Cassinelli, 1993) BUT: Prevented by the non-radial forces (Owocki et al. 1996) Bi-stability mechanism (Pelupessy et al. 2000) BUT: Does not deliver high enough density contrast Existence of a slow solution in line-driven winds (Cure´ 2004) combined with the bi-stability mechanism produces equatorial density enhancements of the right order (Cure´ et al. 2005)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks ⇓ To unveil possible mechanism(s) that form B[e] supergiant stars’ disks, we need to know their structure and kinematics

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants

1 BUT: Terminal velocities of the slow-wind (200 - 300 km s− ) are more than 10 1 times higher than observed (10 - 30 km s− )

⇓ To unveil possible mechanism(s) that form B[e] supergiant stars’ disks, we need to know their structure and kinematics

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks CO rings are detached structures (Oksala et al. 2013)

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants - resolving structure and kinematics

Medium-resolution K-band spectra (SINFONI) Model assumptions: Ring of gas with constant TCO and NCO

Surprisingly low TCO values

21 2 Object TCO(K) N (10 cm− ) S 6 2200 200 5 2 S 18 2000±200 8±3 S 65 3200±300 1.5±0.5 S 12 2800±500 2.5±0.5 S 35 3000±200 2 ±0.5 S 73 2800±500 3.5± 0.5 S 134 2200±200 2±1 MWC 137 1900±200 3±2 GG Car 3200±200 5±3 Hen 3-298 2000±200 0.8±0.4 ± ±

Medium-resolution K-band spectra (SINFONI) Model assumptions: Ring of gas with constant TCO and NCO

Surprisingly low TCO values

Discovery of kinematically broadened CO band heads in high-resolution CRIRES K-band spectra of Galactic B[e] supergiants

rotation center of mass

vibration

Tracers for the molecular regions CO band heads form via the superposition of many individual rotation-vibration transitions Convolution with, e.g., a proﬁle from a Keplerian rotating disk creates characteristic band head structure with a blue shoulder and a red peak (Fig. from Carr 1995 for a YSO).

Fits to the CRIRES spectra (Muratore et al. 2012). Model calculations require solely one ring with constant velocity !

CRIRES plus PHOENIX spectra for CPD-52 9243 (Cidale et al. 2012)

Line proﬁles Line proﬁle originating from a narrow rotating ring and a narrow expanding ring are indistinguishable !

v = 30 km/s v = 30 km/s out rot

We need to ﬁnd complementary tracers for the kinematics !

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks EB[kJ /mole ] H C N O Si Mg Fe S Al Ca Ni Na

1100 CO CO 1000 HC ≡CH N2 900 SiO SiO 800 CN CN = 700 H2C CH 2 CS CS NO NO SiS SiS 600 C2 CO-O SO SO 500 H-OH AlO NS O2 SiO-O NS H2 SiC SiN OH SiN S 400 OH SiC Mg-OH FeO 2 CaO H C-CH MgO AlS NiO HS CH 3 3 Si FeS HS CaS NiS CH NH 2 M S 300 SiH NH SiH g FeSi AlH AlN NaO AlSi NiH 200 MgH Ni 2 FeH CaH NaH Al 100 2 Fe 2 0 Mg2 EB[kJ /mole ] Cr P Mn Cl K Ti Co Zn F Cu V Zr 1100 1000 900

800 TiO ZrO 700 AlF VO 600 PO PN ZrF TiF HF VF ZrS SiF ZrC ZrN PC AlCl TiCl NaF CaF 500 PS KF VCl VN CrF F HCl TiN MgF VS CrO P MnF KCl TiC CoF NiF 400 P2 MnO NaCl SiCl CoCl CuF VC CrCl CrN NiCl CaCl TiS CoO ZnF CuCl Si P MnCl FeCl CrS NCl CoS SF NF 300 PH MnS MgCl CrH Cl P SCl KO CoSi CuS CuH V2 MnH OCl CoH ZnCl ClF CuO Al P Cl 2 TiH 200 KH ZnS OF Co 2 ZnO F Cu2 Cr 2 Ti 2 2 100 ZnH K2 0 Mn 2 Zn 2

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Chemistry in the disks of B[e] supergiants

lolog 12 H

11 He

9 O C Ne 8 N Mg SiSi FeFe S 7 ArAr AlAl CaCa NiNi Na 6 CrCr P MnMn ClCl K 5 TiTi CoCo ZnZn F Cu 4 V

EB[kJ /mole ] H C N O Si M Fe S Al Ca Ni Na lolo g g 1100 CO CO 12 H 1000 HC ≡CH N2 900 SiO SiO He 800 CN CN 11 = 700 H2C CH 2 CS CS NO NO SiS SiS 600 C2 CO-O SO SO 500 H-OH AlO 10 NS O2 SiO-O NS H2 SiC SiN OH SiN S 400 OH SiC Mg-OH FeO 2 CaO H C-CH MgO AlS NiO HS CH 3 3 Si FeS HS CaS NiS CH NH 2 M S 300 SiH NH SiH g FeSi AlH AlN NaO 9 AlSi NiH 200 MgH Ni 2 O FeH CaH NaH Al C 100 2 Fe 2 Ne Mg2 8 0 N EB[kJ /mole ] Mg SiSi FeFe Cr P Mn Cl K Ti Co Zn F Cu V Zr S 1100 7 1000 ArAr AlAl CaCa NiNi 900 Na TiO 6 800 ZrO CrCr 700 P MnMn AlF VO ClCl 600 PO PN ZrF TiF HF VF ZrS K SiF ZrC ZrN C CaF 5 TiTi CoCo 500 P S AlCl KF TiCl NaF P TiN VCl VN CrF FP MnF HCl MgF VS CrO KCl TiC CoF NiF C F VC ZnZn F 400 P2 MnO NaCl SiCl CoCl u CrCl CrN NiCl CaCl TiS CoO ZnF CuCl Si P MnCl FeCl Cu CrS NCl CoS SF NF 300 PH MnS MgCl V CrH Cl P SCl KO CoSi CuS CuH V2 4 MnH OCl CoH ZnCl ClF CuO Al P Cl 2 TiH 200 KH ZnS OF Co 2 ZnO F Cu2 Cr 2 Ti 2 2 100 ZnH K2 0 Mn 2 Zn 2

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Chemistry in the disks of B[e] supergiants Searching for SiO band emission Computation of theoretical band structures to localize the wavelength region of the expected emission High-resolution (CRIRES, R = 50 000) L-band observations centered on the ﬁrst four SiO band heads for 4 B[e] supergiants with conﬁrmed CO band emission

First three SiO band heads detected in CPD-52 9243 (Kraus et al. 2015)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Object i vrot(CO) vrot(SiO) CPD-52 9243 46 36 35.5 CPD-57 2874 60 130 110 HD 327083 50 86 78 HD 62623 38 53 48

Decrease in velocity with distance from the star suggests Keplerian rotation of the disk.

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Chemistry in the disks of B[e] supergiants

SiO band heads Detection of the ﬁrst SiO band head in three more B[e] supergiants.

Object i vrot(CO) vrot(SiO) CPD-52 9243 46 36 35.5 CPD-57 2874 60 130 110 HD 327083 50 86 78 HD 62623 38 53 48

Decrease in velocity with distance from the star suggests Keplerian rotation of the disk.

Spectrally and spatially resolved AMBER/VLTI observations reveal a Keplerian rotating disconnected gas disk around HD 62623 (Millour et al. 2011).

pole−onedge−on intermediate spiral arm

Disk tracers in FEROS spectra of Magellanic Cloud B[e] supergiants (from Aret et al. 2012)

CPD-52 9243 CPD-57 2874 GG Car HD 62623 Hen 3-298 1.4 1.2 1.15 [OI] [OI] [OI] [OI] 2.2 [OI] 1.3 1.20 6300 6300 6300 1.10 6300 6300 1.2 1.1 1.8 1.10 1.05 1.1 1.4 1.0 1.0 1.00 1.00 1.0 4.0 1.8 [CaII] [CaII] 1.15 [CaII] [CaII] [CaII] 7291 1.3 7291 7291 7291 7291 1.6 1.40 3.0 1.2 1.10 1.4 1.20 2.0 1.2 1.1 1.05 1.0 1.0 1.00 1.00 1.0 4.0 1.8 [CaII] [CaII] 1.15 [CaII] [CaII] [CaII] Normalized ﬂux Normalized 7324 1.3 7324 7324 7324 7324 1.6 1.40 3.0 1.2 1.10 1.4 1.20 2.0 1.2 1.1 1.05 1.0 1.0 1.00 1.00 1.0 −80 −40 0 40 80 −150 −50 0 50 150 −150 −50 0 50 150 −100 −50 0 50 100 −60−40−20 0 20 40 60 Radial velocity (km s-1)

Disk tracers in FEROS spectra of Galactic B[e] supergiants suggesting multiple components

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Table: Ring distances for M = 27 M . ∗ 1 Ring Element(s) 3rot (km s− ) r (AU) 1 [Ca II] & [O I] λ 5577 39 15.7 2 [O I] λ 6300 & CO 34 20.7 3 [Ca II] & [O I] λ 5577 22 45.3 4 [O I] λ 6300 16 93.6

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants - resolving structure and kinematics

Multiple rings around LHA 120-S 73 ! Line proﬁles consist of two ring components !

4 rings of⇓ alternating density (Kraus et al., submitted)

Multiple rings around LHA 120-S 73 ! Line proﬁles consist of two ring components !

4 rings of⇓ alternating density (Kraus et al., submitted)

Table: Ring distances for M = 27 M . ∗ 1 Ring Element(s) 3rot (km s− ) r (AU) 1 [Ca II] & [O I] λ 5577 39 15.7 2 [O I] λ 6300 & CO 34 20.7 3 [Ca II] & [O I] λ 5577 22 45.3 4 [O I] λ 6300 16 93.6

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Variable CO band intensity of LHA 120-S 73 (Kraus et al. submitted)

⇓ Inhomogeneities in CO density!

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants - CO band variability

Change in CO band head structure in HD 327083 within 1 month (Kraus et al. 2013)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks ⇓ Inhomogeneities in CO density!

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants - CO band variability

Change in CO band head structure in HD 327083 within 1 month (Kraus et al. 2013)

Variable CO band intensity of LHA 120-S 73 (Kraus et al. submitted)

Change in CO band head structure in HD 327083 within 1 month (Kraus et al. 2013)

Variable CO band intensity of LHA 120-S 73 (Kraus et al. submitted)

⇓ Inhomogeneities in CO density!

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Rotating clumpy CO rings (Kraus et al. in prep.) ⇑ ⇓

142

0.4 114

0.2 67

0.0 32

19 Arcseconds Offset (North) −0.2 9

-3 −0.4

0.4 0.2 0.0 −0.2 −0.4 -4 Arcseconds Offset (East)

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants - CO band variability The Galactic B[e] supergiant MWC 137

Narrow band Hα image. Ring nebula diameter: 7000. (Marston & McCollum 2008)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Rotating clumpy CO rings (Kraus et al. in prep.) ⇑ ⇓

142

0.4 114

0.2 67

0.0 32

19 Arcseconds Offset (North) −0.2 9

-3 −0.4

0.4 0.2 0.0 −0.2 −0.4 -4 Arcseconds Offset (East)

Narrow band Hα image. Ring nebula diameter: 7000. (Marston & McCollum 2008)

Rotating clumpy CO rings (Kraus et al. in prep.) ⇑ ⇓

142

0.4 114

0.2 67

0.0 32

Narrow band Hα image. Ring 19 Arcseconds Offset (North) nebula diameter: 7000. −0.2 9 (Marston & McCollum 2008) 1

-3 −0.4

0.4 0.2 0.0 −0.2 −0.4 -4 Arcseconds Offset (East)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks No CO band emission is seen in observations from 2010 - 2013 (Liermann et al. 2014).

1.3 MWC 84 CO (2-0) CO (3-1) CO (2-0) 12 12 13 1.2 LBT/Luci I 2010 (nflux + c)

1.1

Gemini/GNIRS 2011 (nflux + c)

normalized flux1.0 [a.u.] Gemini/GNIRS 2013 2.28 2.30 2.32 2.34 λ [µm]

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants - CO band variability

sion and longer wavelength data is sparse. Additional sources of error include the distance estimate, and the extrapolated value 18 for the mass absorption coefﬁcient (where the mass absorption m; Soifer et al. 1986). Assuming a gas to dust ratio of 100:1 we 16 for the total mass of ejecta associated with the cold dust. Adopting a mass loss rate for the (e.g. Waters 1986) such a mass 14 years to accumulate. Given the lifetime for years such a mass could be lost 2.3 2.35 2.4 2.45 2.5

CI Cam displays CO band emission one month after its outburst in March 1998 (Clark et al. 1999)

No CO band emission is seen in observations from 2010 - 2013 (Liermann sion and longer wavelength data is sparse. Additional sources of error include the distance estimate, and the extrapolated value et al. 2014). 18 for the mass absorption coefﬁcient (where the mass absorption m; Soifer et al. 1986). Assuming a gas to dust ratio of 100:1 we 16 1.3 for the total mass of ejecta as- MWC 84 CO (2-0) CO (3-1) CO (2-0) sociated with the cold dust. Adopting a mass loss rate for the 12 12 13 14 (e.g. Waters 1986) such a mass 1.2 years to accumulate. Given the lifetime for LBT/Luci I 2010 (nflux + c) years such a mass could be lost 2.3 2.35 2.4 2.45 2.5

1.1

Gemini/GNIRS 2011 (nflux + c)

normalized flux1.0 [a.u.] CI Cam displays CO band emission one Gemini/GNIRS 2013 month after its outburst in March 1998 2.28 2.30 2.32 2.34 (Clark et al. 1999) λ [µm]

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Sudden appearance of pronounced CO bands in October 2011 (Oksala et al. 2012).

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions The disks of B[e] supergiants - CO band variability

LHA 115-S 65 did not show CO band emission during the past 30 years (McGregor et al. 1989) and also not in January 2011.

Sudden appearance of pronounced CO bands in October 2011 (Oksala et al. 2012).

LHA 115-S 65 did not show CO band emission during the past 30 years (McGregor et al. 1989) and also not in January 2011.

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Binary interaction 16 B[e] supergiant candidates in the Galaxy. ∼ Only 4 are found in close binaries MWC 300 (Wang et al. 2012) GG Car (Marchiano et al. 2012; Kraus et al. 2013) HD 62623 (Millour et al. 2011) HD 327083 (Wheelwright 2013) In these systems the rings were found to be circumbinary MWC 314 was found to be a semi-detached binary, in which the primary (the B[e] component) is now re-classiﬁed as LBV (Lobel et al. 2013)

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Formation mechanism(s) of B[e] supergiant stars’ disks

Diversity in observed variabilities speaks in favor of different mechanisms leading to the disk/ring formation interaction (up to merging) in a close binary system phases of eruptions, similar to LBVs, but with concentration towards equatorial regions

Binary interaction 16 B[e] supergiant candidates in the Galaxy. ∼ Only 4 are found in close binaries MWC 300 (Wang et al. 2012) GG Car (Marchiano et al. 2012; Kraus et al. 2013) HD 62623 (Millour et al. 2011) HD 327083 (Wheelwright 2013) In these systems the rings were found to be circumbinary MWC 314 was found to be a semi-detached binary, in which the primary (the B[e] component) is now re-classiﬁed as LBV (Lobel et al. 2013)

Binary without interaction The object HD 87643 was resolved by interferometry to be a binary, but the disk is circumprimary (Millour et al. 2009)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks However, one SMC object, LHA 115-S 6, has a companion, which appears less massive but more evolved than the B[e] component

B[e] component as a result of binary merger in a triple system? (Zickgraf et al. 1996; Podsiadlowski 2006)

Z ! !!"

B V

M M

" "

a a

R R

B A

M sin i M

sin i log g

log g R R

sin i

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Formation mechanism(s) of B[e] supergiant stars’ disks B[e] supergiants in the Magellanic Clouds 11 conﬁrmed and 3 new candidates in the LMC 4 conﬁrmed and 4 new candidates in the SMC None of them was found to be in a close binary.

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks B[e] component as a result of binary merger in a triple system? (Zickgraf et al. 1996; Podsiadlowski 2006)

Z ! !!"

B V

M M

" "

a a

R R

B A

M sin i M

sin i log g

log g R R

sin i

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks B[e] component as a result of binary merger in a triple system? (Zickgraf et al. 1996; Podsiadlowski 2006)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks

Z ! !!"

B V

M M

" "

a a

R R

B A

M sin i M

sin i log g

log g R R

sin i

sin i Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Formation mechanism(s) of B[e] supergiant stars’ disks B[e] supergiants in the Magellanic Clouds 11 conﬁrmed and 3 new candidates in the LMC 4 conﬁrmed and 4 new candidates in the SMC None of them was found to be in a close binary. However, one SMC object, LHA 115-S 6, has a companion, which appears less massive but more evolved than the B[e] component

B[e] component as a result of binary merger in a triple system? (Zickgraf et al. 1996; Podsiadlowski 2006)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks

Z ! !!"

B V

M M

" "

a a

R R

B A

M sin i M

sin i log g

log g R R

sin i

sin i Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Formation mechanism(s) of B[e] supergiant stars’ disks B[e] supergiants in the Magellanic Clouds The SMC star LHA 115-S 18 displays strong variability, similar to LBVs It is a conﬁrmed X-ray source (Clark et al. 2013, Maravelias et al. 2014) It displays Raman scattered emission (Torres et al. 2012), which is typically seen only in symbiotic systems (e.g., Leedjarv¨ et al. 2016)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks B[e] supergiants are⇓ surrounded by detached, often multiple and/or clumpy rings of gas and dust. Gaps in the disks and Keplerian rotation is also conﬁrmed by spectrally and spatially resolved interferometric observations (Meilland et al. 2013; Wheelwright et al. 2012, 2013; Cidale et al. 2012).

⇓ Disks of B[e] supergiants are not formed by an equatorially outﬂowing wind. Other scenarios: binary interaction (merger ?), or (pulsationally-triggered ?) LBV-like eruptions, or something else we did not consider yet...

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Conclusions

Combined kinematics obtained from different tracers ([CaII], [OI], CO, SiO, ...) indicate Keplerian rotation of the gas. CO band emission marks the inner edge of the molecular disk region.

In all objects, temperatures are low (TCO 3000 K) compared to the CO dissociation temperature (T 5000 K)≤ CO,diss '

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Gaps in the disks and Keplerian rotation is also conﬁrmed by spectrally and spatially resolved interferometric observations (Meilland et al. 2013; Wheelwright et al. 2012, 2013; Cidale et al. 2012).

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Conclusions

Combined kinematics obtained from different tracers ([CaII], [OI], CO, SiO, ...) indicate Keplerian rotation of the gas. CO band emission marks the inner edge of the molecular disk region.

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks ⇓ Disks of B[e] supergiants are not formed by an equatorially outﬂowing wind. Other scenarios: binary interaction (merger ?), or (pulsationally-triggered ?) LBV-like eruptions, or something else we did not consider yet...

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Conclusions

Combined kinematics obtained from different tracers ([CaII], [OI], CO, SiO, ...) indicate Keplerian rotation of the gas. CO band emission marks the inner edge of the molecular disk region.

In all objects, temperatures are low (TCO 3000 K) compared to the CO dissociation temperature (T 5000 K)≤ CO,diss ' B[e] supergiants are⇓ surrounded by detached, often multiple and/or clumpy rings of gas and dust. Gaps in the disks and Keplerian rotation is also conﬁrmed by spectrally and spatially resolved interferometric observations (Meilland et al. 2013; Wheelwright et al. 2012, 2013; Cidale et al. 2012).

Combined kinematics obtained from different tracers ([CaII], [OI], CO, SiO, ...) indicate Keplerian rotation of the gas. CO band emission marks the inner edge of the molecular disk region.

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Kinematical information from more tracers (molecules!) is needed Computation of molecule condensation sequences in the environments/disks IFU observations to spatially resolve the geometry and structure of the gas (Galactic objects) Time-series of high-resolution observations of the CO band emission to constrain the distribution of gaps/clumps (extragalactic objects) Development of new scenarios for mass loss (ejection) and mass accumulation in the environments (equatorial plane) of evolved massive stars

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Conclusions

Outlook and future work Homogeneous set of observations for all objects is needed!

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Computation of molecule condensation sequences in the environments/disks IFU observations to spatially resolve the geometry and structure of the gas (Galactic objects) Time-series of high-resolution observations of the CO band emission to constrain the distribution of gaps/clumps (extragalactic objects) Development of new scenarios for mass loss (ejection) and mass accumulation in the environments (equatorial plane) of evolved massive stars

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Conclusions

Outlook and future work Homogeneous set of observations for all objects is needed! Kinematical information from more tracers (molecules!) is needed

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks IFU observations to spatially resolve the geometry and structure of the gas (Galactic objects) Time-series of high-resolution observations of the CO band emission to constrain the distribution of gaps/clumps (extragalactic objects) Development of new scenarios for mass loss (ejection) and mass accumulation in the environments (equatorial plane) of evolved massive stars

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Conclusions

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Time-series of high-resolution observations of the CO band emission to constrain the distribution of gaps/clumps (extragalactic objects) Development of new scenarios for mass loss (ejection) and mass accumulation in the environments (equatorial plane) of evolved massive stars

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Conclusions

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks Development of new scenarios for mass loss (ejection) and mass accumulation in the environments (equatorial plane) of evolved massive stars

Outline Introduction The disks of B[e] supergiants Formation mechanism(s) of B[e] supergiant stars’ disks Conclusions Conclusions

Outlook and future work Homogeneous set of observations for all objects is needed! Kinematical information from more tracers (molecules!) is needed Computation of molecule condensation sequences in the environments/disks IFU observations to spatially resolve the geometry and structure of the gas (Galactic objects) Time-series of high-resolution observations of the CO band emission to constrain the distribution of gaps/clumps (extragalactic objects)

M. Kraus Probing the structure and dynamics of B[e] supergiant stars’ disks