Rotational periods of the components in Symbiotic Binary

Stars

Radoslav K. ZamanovInstitute of Astronomy, Bulgarian Academy of Sciences

in collaboration withM.F. Bode (Liverpool, UK),

C.H.F. Melo (ESO, Chile)A. Gomboc (Ljubliana, Slovenia),

R. Bachev, I. K. Stateva, R.Konstantinova-Antova (Sofia, Bulgaria)

03'2012

Symbiotic binary star = Red Giant + White Dwarf

Symbiotic stars are interacting binaries consisting of red giant transferring mass onto a white dwarf.

We are investigating the projected rotational velocities of the mass donors. Our aims are:

• To check theoretical prediction that the red giants in these binaries are co-rotating (for objects with known periods).

• To perform comparative analysis and to check if they are faster rotators (comparing with isolated giants and those in wide binary systems).

• To give clues for binary periods, individual mass loss rates, select candidates for X-ray observations.

Observations: 40 symbiotic stars have been observed with the 2.2m telescope

(ESO, La Silla) + FEROS spectrograph at resolution 50000.

Our sample: All objects from the Symbiotic star catalogue with

0h<R.A.<24h, Declination < 00, and brighter than V< 12.5 mag.

From literature -12 northern symbiotics. Our sample is flux limited, there should be no biases in

rotation.

ESO – La Silla

Altitude H=2340 m

ESO La Silla - 2.2 m telescope

OPTICON gives possibility of the Bulgarian astronomers to use the ESO facilities !!!

Observations: the 2.2m telescope + FEROS spectrograph

FEROS spectrograph

The 39 orders cover wavelengths from 3600 A up to 8900 A.

Observations: the 2.2m telescope + FEROS spectrograph

- resolution 48000; dispersion=0.03 A/pixel

- wavelength coverage: 6300 A in a single exposure (3600 – 8900 AA)

- signal-to-noise ratio = 50; exposure=30 min; V=12 mag;

Comparison – 2.0m telescope Rozhen, Coude spectrograph 0.2 A/px, 200 A in one exposure, S/N=50, exposure=30 min; V=11.3

Fig. Theoretical spectrum and spectra of a few symbiotic in the near IR: wavelength 8760-8850 AA

Fig. Numerical mask and spectra of a few symbiotic in Wavelength interval 8760-8850 AA.

Two examples of the Cross-Correlation Function and the fitting gaussian. Left – AS 316 – v sin i = 9.8 ± 1.5 km/sRight – rapid rotator V417 Cen – v sin i = 75 ± 7.5 km/s

To measure the projected rotational velocity (v sin i) we used the CCF method and numerical template. The width of the CCF is connected (calibrated for FEROS) with the v sin i.

Fig. Check of our methods. The measurements of v-sin-iwith FWHM and CCF methods are in good agreement.

On the basis of their infrared (IR) properties, the symbiotic stars have been classified into stellar continuum (S) and dusty (D or D' ) types.

IR types

S-type - stellar continuum - mass donor is K-M giant

D-type - dusty mass donor is Mira

D'-type – dusty mass donor is F-G giant

D' type v sin i Vcrit critical

[km/s] [km/s]

HD 330036 D' F8III 107.0 160 67%Hen 3-1591 S,D' K1III 23.7 144 StHa190 D' G4III/IV 105.0 191 54%V417 Cen D' G9Ib-II 75.0 105 71%AS 201 D' F9III 25.0 150

Comparison with catalogs

de Medeiros et al. (2002) rotation of Ib supergiant stars 16 supergiant stars G8-K0 Ib-II, v sin i = 1-20 km/s. V417 Cen (G9Ib) - 75 km/s extreme case of very fast rotation.

The catalogue of rotational velocities for evolved stars (de Medeiros et al. 1999) catalogue of rotational velocities for evolved stars100 K1III 90% - vsini< 8 km/s, only 5% - vsini>20 km/s Hen3-1591 23.7 km/s is in the top 5.

F8III-F9III - 5 objects – 10-35 km/s AS 201 (25 km/s) is well within in this range.HD330036 (107 km/s) is an extremely fast rotator.

G3,G4,G5 III-IV – 60 objects - <24 km/sStHa190 (105 km/s) - is again an extremely fast rotator.

D’-type symbiotics are characterized by an earlier spectral type

giant (F-K) and lower dust temperatures. Rotational velocities have been measured for five such stars (Zamanov et al. 2006).

Four of these five objects appeared to be very fast rotators, compared with the catalogues of v sini for the corresponding spectral types. At least three of them rotate at a substantial fraction (≥ 0.5) of the critical velocity. Hence, in D’-type symbiotics, the cool components rotate faster than the isolated giants of the same spectral class (as predicted by Soker 2002).

As a result of rapid rotation, they must have larger mass loss rate, probable enhanced in the equatorial regions. In addition, as a result of the fast rotation, magnetic activity is expected to exist in these giants.

The rotational period of the red giant versus the orbit period for 17 symbiotic stars in our sample with known orbital periods (all they are S-type).

The solid line represents synchronization (Porb=Prot).

Among these 17 objects there are 3, which deviate considerably from co-rotation: MWC560, CD-43 14304 and RS Oph.

Possible reasons for non co-rotation: MWC560 - highly eccentric orbit e=0.70 (+/- 0.05)

CD-43 14304 - highly eccentric orbit e>0.5 ?

RS Oph - ???.

Fig. v sin i versus the spectral type:symbiotic stars – red crosses, black – single giants.

Results:

238 K2III-K5III stars: v sin i = 1.0 - 6.7 km/s mean v sin i =1.70 km/s)The K giants in symbiotic stars: v sin i = 4.5 - 8.9 km/s mean v sin i =7.42 km/s)

The Koslmogorov-Smirnov test gives a probability of 10-4 (K-S statistics =0.60)

K-giant mass donors of symbiotic stars rotate faster than isolated K-giants !!!

Isolated giants spectral classes K2-K5 III (238 objects from catalogues of v sin i)

K2-K5 III giants in symbiotic stars (7 objects, our measurements)

isolated M giants: 1.8 < v sin i < 18 km/s (mean vsini=5.54 km/s)M-giants in symbio 3.0 < v sin i < 52 km/s (mean vsini=9.07 km/s)

The tests gives a probability of 0.09-0.01 that both distributions are coming from the same parent population.

Isolated giants spectral classes M2-M5 III (12 objects from catalogues of v sin i)

M2-M5 III giants in symbiotic stars(28 objects, our measurements mostly)

isolated M giants: 1.8 < v sin i < 18 km/s (mean vsini=5.54 km/s)M-giants in symbio 3.0 < v sin i < 52 km/s (mean vsini=9.07 km/s)

The tests gives a probability of 0.09-0.01 that both distributions are coming from the same parent population.

Isolated giants spectral classes M2-M5 III (12 objects from catalogues of v sin i)

M2-M5 III giants in symbiotic stars(28 objects, our measurements mostly)

isolated M giants: 1.8 < v sin i < 18 km/s (mean vsini=5.54 km/s)M-giants in symbio 3.0 < v sin i < 52 km/s (mean vsini=9.07 km/s)

The tests gives a probability of 0.09-0.01 that both distributions are coming from the same parent population.

Isolated giants spectral classes M2-M5 III (12 objects from catalogues of v sin i)

M2-M5 III giants in symbiotic stars(28 objects, our measurements mostly)

Results of statistical tests:

mean v sin i field symbiotic Kolmogorov-SmirnovK2III-K5III 2.2 km/s 9.5 km/s 7.10-6 (KS statistics =0.90)

M0III-M6III 4.8 9.2 4.10 -7 (KS statistics =0.60)

M0III – M4III 1.10 -9 (KS statistics =0.64)M0III – M3III 2.10 -5 (KS statistics =0.83) M4III-M6III 0.1 (KS statistics =0.44)

Mean v sin i

mean v sin i field symbiotic Kolmogorov-SmirnovM0III-M6III 4.8 9.2 4.10 -7 (KS statistics =0.60)

field symbiotics km/s (N) km/s (N)M0-M1 III 3.7±1.9 (23) 9.9± 2.6 (2)M1.5-M2 III 4.8±4.1 (14) 8.3± 1.1 (3) M2.5-M3 III 5.5 2.0 (8) 6.5 1.8 (4) M3.5-M4 III 2.2 1.0 (3) 7.7 3.3 (7) M4.5-M5 III 5.5 4.0 (5) 7.9 1.7 (9) M5.5-M6 III 12.1 5.1 (4) 7.6 2.0 (6)

±

Discussion:

The reasons for faster rotation in giants in symbiotic systems could be:

- synchronization, if the time spent by the mass-losing star on the giant branch is longer than the synchronization time. In all symbiotic systems with orbital period Porb ≤ 100 years tidal interaction overcomes the angular momentum loss by the wind (Soker 2002).

- accretion during the MS phase of the present red giant: the more massive star in the system, the present WD, had transferred material at the stage when it had been red giant.

- backflowing material: hot component prevents part of the mass blown by the giant from acquiring the escape velocity for the binary system. This fraction of mass may acquire angular momentum, and if it is accreted back by the giant, it spins-up its envelope.

- angular momentum dredge-up when convective envelope approaches the core region of the giant.

- planet engulfment during the giant phase.

• We have measured the projected rotational velocities of 40 symbiotic stars (v sin i) by the means of CCF and FWHM.

• Among 16 symbiotics with known orbit and rotation, there is only one (RS Oph) which is very likely not synchronized.

• Our results show that the mass donors in the symbiotic stars rotate faster than isolated giants. The faster rotation is undoubted for D’-type (yellow) symbiotics and for those harbouring K-giant as mass donor. For those with M giant it is valid till M4III.

CONCLUSIONS:

FUTURE WORK:To strengthen our results, more data on M-type isolated giants and more v sin i measurements of K-type mass donors in symbiotics are desirable. We intend to expand our sample with northern and fainter symbiotic stars.

Open questions:

1. Is there a bimodal distribution of v sin i of the isolated giants?

2. Hen 3-1674 rotates very fast v sin i = 52 km/s

M5III - R=139 Rsun, and mass 1-3 Msun, Vcrit=40-60 km/s. What is this object? a monster? or just an error somewhere?

3. Is there a connection between the rotation of the red giant and the density of the circum binary nebula and mass accretion rate?

What is the rotation of the white dwarfs in symbiotic stars?

What is the rotation of the white dwarfs in symbiotic stars?

MWD RWD

dM TNR P rot

[MꙨ] [km] [MꙨ] []

0.2 14000 1.47e-2 67 sec 0.3 11480 5.46e-3 172 sec 0.4 10440 2.80e-3 334 sec 0.5 9220 1.36e-3 10 min 0.6 8350 7.64e-4 17 min 0.7 7660 4.62e-4 27 min 0.8 6820 2.55e-4 45 min 0.9 6120 1.47e-4 71 min 1.0 5360 7.77e-5 116 min 1.1 4660 4.05e-5 190 min 1.2 3830 1.68e-5 6 h 1.3 2780 4.35e-6 15 h 1.35 2090 1.33e-6 32 h 1.38 1400 2.56e-7 4 days

    

Zamanov R.K., Bode M.F., Melo C.H.F., Stateva I.K., Bachev R., Gomboc A., Konstantinova-Antova R., Stoyanov, K. A. Rotational velocities of the giants in symbiotic stars - III. Evidence of fast rotation in S-type symbiotics 2008 MNRAS.390..377

Zamanov R. K., Bode M. F., Melo C. H. F., Stateva I.K., Bachev R., Gomboc A., Konstantinova-Antova, R.; Stoyanov, K. A. Rotational velocities of the giants in symbiotic stars - III. Evidence of fast rotation in S-type symbiotics 2007 MNRAS.380.1053

Zamanov, R. K.; Bode, M. F.; Melo, C. H. F.; Porter, J.; Gomboc, A.; Konstantinova-Antova, R. Rotational velocities of the giants in symbiotic stars - I. D'-type symbiotics 2006 MNRAS.365.1215

Zamanov, R. K.; Konstantinova-Antova, R.; Bode, M. F.; Melo, C. H. F.; Gomboc A., Bachev R., Rotation of the mass donors in symbiotic stars

V Bulgarian Serbian astronomical conference Zamanov R., Tidal Interaction in High Mass X-ray Binaries and Symbiotic Stars

2011 BlgAJ..15...19Z

in collaboration with

N. A. Tomov (NAO Rozhen, BG), M.F. Bode (Liverpool, UK),

C.H.F. Melo (ESO, Chile)A. Gomboc (Ljubliana, Slovenia),

R. Bachev, I. K. Stateva, K.A. Stoyanov, R.Konstantinova-Antova (Sofia, Bulgaria)

THE END