COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 780 Konkoly Observatory Budapest 1973 April 12 POLARIMETRY OF SELECTED SPECTROSCOPIC BINARIES In an ongoing broad-band photoelectric investigation of linear polarization, eighteen spectroscopic binaries have been surveyed to date. All observations have been made with the Pennsylvania two-channel polarimeter (Wolf 1972) attached to the 72- cm cassegrain reflector. The observational and reduction methods are adaptations of those of Clarke (1965). The results have been freed of the instrumental polarization by the usual technique of observing standard unpolarized stars (Serkowski 1965, 1968). In the accompanying table we summarize the limits of the observations obtained thus far. The successive columns give: 1, the HD number if available; 2, the binary name; 3 and 4, the filter and the number of observations with that filter, respectively; 5, the minimum observed polarization and its probable error; 6, the maximum observed polarization and its probable error; 7, the minimum observed angle of the plane of polarization in the equatorial system and its probable error; and 8, the maximum observed angle of the plane of polarization in the equatorial system and its probable error. For a given filter, the values of theta^m_E and theta^M_E do not necessarily correspond to the tabulated values of P_m and P_M. The intention here is to demonstrate the ranges in measured values of P and theta_E in order to indicate whether an object displays variable polarization. If P is very small or has a large probable error, the result is an indeterminate value for theta_E The observations suggest that LY Aur, SZ Cam, RS CVn, SX Cas, AO Cas, KS Per, o Per, phi Per, nu Sgr, and zeta Tau exhibit time - dependent polarization. This is interpreted to mean that in addition to any interstellar component, these systems possess at least one intrinsic component of polarization. Variable components of polarization for LY Aur, SZ Cam, RS CVn, SX Cas, AO Cas, KS Per, and o Per have not been detected before. For AO Cas, the observations indicate that this binary possesses an asymmetric, homogeneous, systemic electron-scattering envelope and that the change in polarization arises from a combination of the variations in the stellar flux and apparent geometry of the envelope as the system revolves and rotates. Although the observations are few, there are intimations that WW Aur, YY Gem, and Plaskett's star may also possess time-dependent intrinsic components of polarization and hence some sorts of distribution of scattering circumstellar material. In the case of YY Gem, a variable component of intrinsic polarization may be indicative of some vestige of pre-main-sequence activity. Within the observational errors, alpha And, beta Aur, beta Per, BD+16d516, and TX UMa appear to have no variable component of polarization. In fact, beta Aur and beta Per seem to possess negligibly small polarization. The wavelength dependences of the polarization for nu Sgr and zeta Tau agree with Coyne and Kruszewski's (1969) results but at this time we make no comment concerning the dependence for AO Cas and LY Aur. Polarimetric observations are continuing for all the above systems and additional objects are being added to the survey. R.J. PFEIFFER R.H. KOCH Department of Astronomy University of Pennsylvania Philadelphia, Pennsylvania 19104 References: Clarke, D. 1965, M.N.R.A.S. 129, 71. [BIBCODE 1965MNRAS.129...71C ] Coyne, G.V. and Kruszewski, A. 1969, Astron.J. 74. 528. [BIBCODE 1969AJ.....74..528C ] Serkowski, K. 1965, Astrophys.J. 141, 1340. [BIBCODE 1965ApJ...141.1340S ] Serkowski, K. 1968, ibid. 154, 115. [BIBCODE 1968ApJ...154..115S ] Wolf, G.W. 1972, Astron.J. 77, 576. [BIBCODE 1972AJ.....77..576W ] ------------------------------------------------------------------------------------------- HD BINARY FIL. n P_m(%) P_M(%) theta^m_E theta^M_E Remarks ------------------------------------------------------------------------------------------- 358 alpha And V 3 0.17+-0.08 0.32+-0.05 4d+-13d 176d+-4d 1337 AO Cas U 2 0.52 0.08 0.66 0.04 42 2 49 3 1337 AO Cas B 7 0.55 0.09 0.73 0.07 30 4 43 2 var. 1337 AO Cas V 16 0.58 0.05 0.87 0.05 41 3 57 3 var. 1337 AO Cas R 1 0.41 0.07 ---- 38 4 ---- 10516 phi Per V 10 0.77 0.07 1.42 0.12 32 2 83 3 var. 19356 beta Per V 2 0.08 0.07 0.14 0.06 69 12 93 24 23180 o Per B 3 0.46 0.05 0.76 0.08 23 5 25 3 var. 23180 o Per V 10 0.31 0.07 0.58 0.06 17 4 34 4 var. --- +16d516 R 2 0.20 0.21 0.40 0.15 28 31 159 11 25638 SZ Cam V 4 6.20 0.07 6.44 0.07 140.2 0.3 141.1 0.3 var. 30353 KS Per V 6 1.84 0.09 2.18 0.12 147 1 161 1 var. 35921 LY Aur U 1 1.75 0.11 ---- 147 2 -- - 35921 LY Aur B 1 2.12 0.10 -- - 144 1 - 35921 LY Aur V 10 1.49 0.07 2.01 0.06 140 1 147.4 0.7 var. 35921 LY Aur R 2 1.37 0.12 1.78 0.11 140 2 144 2 var. 37202 zeta Tau U 2 1.08 0.09 1.13 0.06 26 2 28 2 37202 zeta Tau B 2 1.44 0.06 1.45 0.06 29 1 34 1 37202 zeta Tau V 11 0.93 0.08 1.35 0.04 23 3 34 1 var. 37202 zeta Tau R 9 1.03 0.05 1.34 0.06 29 2 36 1 var. 40183 beta Aur V 2 0.05 0.08 0.12 0.06 78 43 91 13 40183 beta Aur R 1 0.03 0.06 - -- 83 55 -- - 46052 WW Aur V 3 0.08 0.05 0.25 0.04 27 15 126 10 var. 47129 Plaskett's V 3 0.88 0.08 0.99 0.05 141 3 158 3 var. --- YY Gem R 2 0.27 0.08 0.97 0.11 65 8 132 3 var. 93033 TX UMa B 2 0.08 0.07 0.15 0.03 16 30 167 6 93033 TX UMa V 3 0.07 0.07 0.23 0.06 23 11 80 34 114519 RS CVn V 8 0.06 0.06 0.58 0.11 46 12 143 20 var. 181615 nu Sgr U 2 0.72 0.13 0.89 0.05 163 2 172 5 181615 nu Sgr B 3 0.93+-0.08 1.10+-0.11 157+-2 172+-3 var. 181615 nu Sgr V 3 0.82+-0.07 1.01+-0.05 173+-3 176+-2 var. 181615 nu Sgr R 2 0.73 0.07 0.80 0.08 176 3 177 3 232121 SX Cas B 1 0.76 0.15 -- - 61 5 --- 232121 SX Cas V 4 0.36 0.08 0.77 0.10 0 6 47 5 var. 232121 SX Cas R 16 0.27+-0.10 0.88+-0.08 22d+-5d 59d+-10d var. -------------------------------------------------------------------------------------------