nevans@cfa.harvard.edu

September 1999

This seemed like an appropriate time to summarize the results of the Cepheid radial velocity studies which I have been carrying out at DDO for nearly 30 years now. The main thrust of the program has been radial velocity measurements of Cepheids, particularly binaries. This has been combined with satellite (IUE and HST) velocity work to measure Cepheid masses. These are still the best fiducial for testing evolutionary tracks of evolved objects, as well as quantitative measurements of primary distance indicators. In addition the program has produced a definitive distribution of mass ratios in intermediate mass binaries, important information on star formation. Finally the combined ground-based and satellite studies leave us poised to make use of newly resolved binary systems. The one program which I am currently working on is to try to measure the velocities of the bright companions of 3 Cepheids near 4000 A. This is particularly well-suited to DDO, since it requires spectral subtraction. If we (Evans, Vinko, Kiss, and Beattie) succeed - and I did many years ago with SU Cyg--three systems will be strong candidates for both resolution and HST velocity work. The program started in the 1970's and is still continuing. In 1989, a new mode of service observing has been started when I was associated with the Institute for Space and Terrestrial Science in Toronto. The first papers from this mode started appearing in 1994; since then we have had 6 papers in refereed journals and 9 papers in conference proceedings. The following persons contibuted to the program: Tom Bolton, John Percy, Ben Sugars, Jozsef Vinko, Ron Lyons, Jim Thomson, Irina Dashevsky and Andrzej Udalski. Below I include a list of publications, those either containing DDO data, or very directly following from DDO results such as orbits. (A couple of Southern stars are thrown in because they complete the Cepheid information.) DDO has been a wonderful facility to work on the multi-year orbits of Cepheids, and without the orbits, the breakthrough satellite results (double-lined spectroscopic binaries) would not have been possible. Nancy

- Evans, N.R. Light and Radial Velocity Observations of Classical Cepheids, ApJS, 32, 399-407, 1976.
- Evans, N.R. Wesselink Radii for Classical Cepheids, ApJ, 209, 135-40, 1976.
- Evans, N.R. An Observational Check on the Phase Shifts Determined by the Angular Diameter Method of Distance Determination for Classical Cepheids, MNRAS, 181, 85-87, 1977.
- Percy, J.R. and Evans, N.R. HR 7308: A Unique Cepheid, AJ, Journal, 85, 1509-1512, 1980.
- Evans, N.R. A Search for Radial-Velocity Variations in Epsilon Leonis (HD 84441), PASP, 94, 564-66, 1982.
- Evans, N.R. A Search for Light-Time Effects in Binary Cepheids: AW Persei, ApJ, 272, 214, 1983.
- Evans, N.R. X Cygni: Duplicity, Period Stability, and Atmospheric Velocity Structure, ApJ, 281, 760, 1984.
- Turner, D.G. and Evans, N.R. An Investigation of the Stellar Association Containing the 1.95 Day Cepheid SU Cassiopeiae, ApJ, 283, 254, 1984.
- Kamper, K.W., Evans, N.R. and Lyons, R.W. Confirmation of the Decreased Pulsational Amplitude of Polaris, JRASC, 78, 173, 1984.
- Evans, N.R. and Lyons, R.W. Radial Velocity Curves for the Classical Cepheids T Vulpeculae, TT Aquilae, and Y Ophiuchi, AJ, 92, 436, 1986.
- Welch, D.L., Evans, N.R., Lyons, R.W., Harris, H.C., Barnes, T.G. III, Slovak, M.H., Moffett, T.J. The Orbit of the Classical Cepheid U Aquilae, PASP, 99, 610, 1987.
- Evans, N.R. The Orbit of the Classical Cepheid SU Cygni, ApJS, 66, 343, 1988.
- Evans, N.R. A Search for the Binary Companion of Polaris, PASP, 100, 724, 1988.
- Welch, D.L. and Evans, N.R., The Orbit of the Classical Cepheid AW Persei, AJ, 97, 1153, 1989.
- Evans, N.R. The Binary Companion of the Classical Cepheid AW Per, AJ, 97, 1737, 1989.
- Evans, N.R., Welch, D.L., Scarfe, C.D. and Teays, T.J., The Orbit and Companions of the Classical Cepheid FF Aql, AJ, 99, 1598, 1990.
- Evans, N. R. and Bolton, C.T. , The Mass of the Classical Cepheid SU Cygni, ApJ, 356, 630, 1990.
- Evans, N.R., The Orbit and Colors of the Cepheid S Mus, PASP, 102, 551, 1990.
- Udalski, A. and Evans, N.R., The Visual Companion of the Classical Cepheid FF Aql, AJ, 106, 348, 1993.
- Evans, N.R., Welch, D.L., Slovak, M. H., Barnes, T.G., and Moffett, T.J., The Orbit and Companion of the Cepheid S Sge: A Probable Triple System, AJ, 106, 1599, 1993.
- Evans, N. R. and Lyons, R. The Binary System Containing the Classical Cepheid T Mon, AJ, 107, 2164, 1994.
- Evans, N. R., Massa, D., and Teays, T. J. S Mus B Revisited, AJ, 108, 2251, 1994.
- Evans, N. R. and Udalski, A. Resolved Companions of Classical Cepheids, AJ, 108, 653, 1994.
- Evans, N. R. The Mass Ratios of Cepheid Binaries, ApJ, 445, 393, 1995.
- Evans, N. R., Holberg, J. B., and Polidan, R. S. Voyager Observations of the Companion of the Classical Cepheid S Muscae, AJ, 112, 264, 1996
- Sugars, B. J. A. and Evans, N. R. Z Lac: Orbital Circularization in Supergiants, AJ, 112, 1670, 1996.
- B"ohm--Vitense, E., Evans, N. R., Carpenter, K., Beck--Winshatz, B., and Robinson, R. The Mass of the Classical Cepheid S Muscae'', ApJ, 477, 916, 1997.
- Evans, N. R. and Sugars, B. J. A. The Orbit of the Classical Cepheid V350 Sgr, AJ, 113, 792, 1997.
- N. R. Evans, E. B"ohm-Vitense, K. Carpenter, B. Beck-Winchatz, and R. Robinson, The Mass of the Classical Cepheid V350 Sgr, PASP, 109, 789, 1997.
- B"ohm-Vitense, E., Evans, N. R. Carpenter, K., Beck-Winchatz, B., Morgan, S., and R. Robinson, The Dynamical Mass of the Beat Cepheid Y Carinae and Stellar Opacities, AJ, 114, 1176, 1997.
- Vinko, J., Evans, N. R., Kiss, L. L., and Szabados, L., Spectroscopic Survey of Field Type II Cepheids", MNRAS, 296, 824, 1998.
- N. R. Evans, E. B"ohm-Vitense, K. Carpenter, B. Beck-Winchatz, and R. Robinson, The Mass of the Classical Cepheid U Aql, ApJ, 494, 768, 1998.
- E. Bohm-Vitense, N.R. Evans, K. Carpenter, M. Albrow, P. Cottrell, R., Robinson, and B. Beck-Winchatz, The Mass of the Cepheid Binary V 636 Sco, ApJ, 505, 903, 1998.
- Wahlgren, G. M. and Evans, N. R. A HgMn Companion to the Cepheid SU Cyg, A&A, 332, L33, 1998.
- Evans, N. R., Carpenter, K., Robinson, R., Massa, D., Wahlgren, G. M., Vinko, J., and Szabados, L. Toward an Orbit for the High Luminosity Cepheid T Mon, Ap.J., in press., Oct. 1999

- Evans, N.R. Microturbulence and Wesselink Radii, in Current Problems in Stellar Pulsation Instabilities, Eds. Fischel, D., Lesh,J.R. and Sparks, W.M., 237-46, Washington, D.C.: NASA Technical Memorandum 80652, 1980.
- Turner, D.G. and Evans, N.R. A Detailed Investigation of the R Association Containing the 1.95 Day Cepheid SU Cassiopeiae, Journal of the Royal Astronomical Society of Canada, abstract, 74, 360, 1980.
- Percy, J.R. and Evans, N.R. HR 7308: A Unique Cepheid. Journal of the Royal Astronomical Society of Canada, abstract, 74, 360, 1980.
- Evans, N.R. Preliminary Orbit and Mass Estimate for the 3.8 Day Classical Cepheid SU Cygni, Bulletin of the American Astronomical Society, 12, 862, 1980
- Turner, D.G. and Evans, N.R. A Detailed Investigation of the R Association Containing the 1.95 Day Cepheid SU Cassiopeia, Bulletin of the American Astronomical Society, 12, 863, 1980.
- Percy, J.R. and Evans, N.R. HR 7308: A Unique Cepheid, Space Science Reviews, 27, 3-4, 1980.
- Evans, N.R. A Search for Light-Time Effects in Binary Cepheids: AW Persei, Journal of the Royal Astronomical Society of Canada, 75 247, 1981.
- Evans, N.R. IAU Circular, 3615, 1981.
- Evans, N.R. A Search for Light-Time Effects in Binary Cepheids: AW Persei Bulletin of the American Astronomical Society, abstract, 14, 634, 1982.
- Evans, N.R. X Cygni: Duplicity, Period Stability, and Atmospheric Velocity Structure, Bulletin of the American Astronomical Society, 15, 876, 1983.
- Evans, N.R. A Search for the Spectroscopic Binary Companion of Polaris using IUE Spectra in 6 Years of IUE, Eds. Kondo, Y. and Mead, J.M., p.428, 1984.
- Evans, N.R. A Search for Cepheid Binaries Using the CaII H and K Lines IAU Colloquium 82, 79, 1984.
- Evans, N.R., Bohm-Vitense, E. and Bolton, C.T. Ultraviolet Observations of the System Containing the Cepheid SU Cygni, Bulletin of the American Astronomical Society, 17, 559, 1985.
- Evans, N.R. and Bolton, C.T. The Mass of the Classical Cepheid SU Cygni in 8 Years of UV Astronomy with IUE, ESA SP-263, p.405, 1986.
- Evans, N.R. and Bolton, C.T. The Mass of the Cepheid SU Cygni, Stellar Pulsations - A Memorial to John P. Cox, Eds. A.N. Cox, W.M. Sparks and S.G. Starrfield. (New York: Springer-Verlag), p.163. 1986.
- Evans, N.R. and Arellano-Ferro, A. The Luminosities of the Binary Cepheids SU Cyg, SU Cas and W Sgr, Stellar Pulsations - A Memorial to John P. Cox, Eds. A.N. Cox, W.M. Sparks and S.G. Starrfield, (New York: Springer-Verlag) p.183, 1986.
- Welch, D.L. and Evans, N.R. The Orbit of the Cepheid AW Per, Bulletin of the American Astronomical Society, 19, 710, 1987.
- Evans, N.R. Cepheid Binaries with Large Mass Radios (M
_{1}/M_{2}) in A Decade of UV Astronomy with the IUE Satellite, (ESA SP-281) 1, 237-239, 1988. - Evans, N.R. and Welch, D.L. The Orbit of the Cepheid AW Per in A Decade of UV Astronomy with the IUE Satellite, (ESA-SP-281) 1, 241-243, 1988.
- Evans, N.R., Cepheid Binaries with Large Mass Ratios, J.R.A.S.C., 82, 281, 1988
- Evans, N.R., Welch, D.L. and Scarfe, C.D., The Orbit and Companions of the Classical Cepheid FF Aql, J.R.A.S.C., 83, 309, 1989.
- Evans, N.R., Slovak, M.H., and Welch, D.L. S Sge: A Cepheid Triple System in The Use of Pulsating Stars in Fundamental Problems in Astronomy, E.G. Schmidt, Ed. (New York: Cambridge Univ. Press), p. 260, 1989.
- Slovak, M.H., Barnes III, T.G., Evans, N.R., Welch, D.L., and Moffett, T.J. The Binary Cepheid S Sagittae Revisited in The Use of Pulsating Stars in Fundamental Problems in Astronomy, E.G. Schmidt, Ed. (New York: Cambridge Univ. Press), p. 284, 1989.
- Evans, N. R. and Udalski, A. The Companions of the Classical Cepheid FF Aql, Proceedings of IAU Colloquium # 135, Complementary Approaches to Double and Multiple Star Research, PASP Conf. Ser., 32, eds. McAlister, H. A. and Hartkopf, W. I., p. 314, 1992
- Evans, N. R. Binary Cepheid: Isochrones and Mass Ratios in Stellar and Circumstellar Astrophysics, PASP Conf. 57, eds. G. Wallerstein and A. Noriega-Crespo, p.137, 1994
- Evans, N. R., and Udalski, A. Resolved Companions of Classical Cepheids, JRASC, 88, 260, 1994
- Sugars, B. J. A. and Evans, N. R. Radial Velocity Studies of Classical Cepheids, JRASC, 88, 270 1994
- Evans, N. R., Cepheid Binaries: Frequency and Mass Ratios, Proc. IAU COll. # 155, PASP Conf. Series, 83, eds. R. S. Stobie and P. A. Whitelock, p. 252, 1995
- Evans, N. R. The Mass Ratios of Cepheid Binaries, Bull. AAS, 1995.
- B"ohm--Vitense, E., Evans, N. R., Beck-Winshatz, B., Carpenter, K., and Robinson, R. The Mass of the Cepheid S Muscae, Bull. AAS, 1996
- Evans, N. R., Sugars, B., and Dashevsky, I. Cassegrain Spectrograph Velocities, 1996, DDO Technical Memorandum #10
- Evans, N. R., Sasselov, D. D., Short, I., and Teays, T. What Does Pulsation do to Upper Atmospheres, 1996, Bull. A. A. S., (HEAD meeting)
- Evans, N. R., B"ohm-Vitense, E., Beck-Winchatz, B., Carpenter, K., and Robinson, R. The Mass of the Classical Cepheid S Muscae, 1998, in The Scientific Impact of the Goddard High Resolution Spectrograph, eds. J. C. Brandt, T. B. Ake, III & C. C. Petersen, ASP Conference Series, Volume 143, 309
- Evans, N. R., B"ohm-Vitense, E., Beck-Winchatz, B., Carpenter, K., and Robinson, R. The Mass of the Classical Cepheid V350 Sgr, 1998, in The Scientific Impact of the Goddard High Resolution Spectrograph, eds. J. C. Brandt, T. B. Ake, III & C. C. Petersen, ASP Conference Series, Volume 143, 313
- B"ohm-Vitense, E., Evans, N. R. Carpenter, K., Robinson, R., and Beck-Winchatz, B. ''The Dynamical Mass of the Beat Cepheid Y Carinae'', 1998, in The Scientific Impact of the Goddard High Resolution Spectrograph, eds. J. C. Brandt, T. B. Ake, III & C. C. Petersen, ASP Conference Series, Volume 143, 317
- N. R. Evans, E. Bohm--Vitense, K. Carpenter, R. Robinson, and B. Beck-Winchatz, New Results on Cepheid Masses, 1996, B.A.A.S., 28, 1399
- Bohm-Vitense, E., Evans, N. R., Carpenter, K., Beck-Winchatz, B., Morgan, S., and Robinson, R. The Dynamical and Beat Masses of the Beat Cepheid Y Carinae, 1998 in Proc. of Half A Century of Stellar Pulsation Interpretations: A Tribute to Arthur N. Cox, eds. P. A. Bradley and J. A. Guzik, ASP Conf. Ser. 135 p. 280
- Evans, N. R., Cepheid Masses and Isochrones, 1999, in Anni Mirabiles: A symposium Celebrating the 90th Birthday of Dorrit Hoffleit, A. G. D. Philip, W. F. van Altena, and A. R. Upgren, (Schnedtady: L. Davis Press), p. 81
- Evans, N. R., Sasselov, D., and C. I. Short, Polaris: What does a Little Pulsation Do to an Atmosphere in 1998, Proceedings of the Tenth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, eds. R. A. Donahue and J. A. Bookbinder, ASP Conf. Ser. 154, 745
- Evans, N. R., Robinson, R. D., Carpenter, K. G., Vinko, J., Massa, D., and Wahlgren, G. M. Toward an Orbit for the High Luminosity Cepheid T Mon, 1998, BAAS, 30,
- Massa, D., Evans, N. R. and Endal, A. S. Cross-dispersion imaging of the Galactic Cepheid binary AW Per. 1999, BAAS, (abstract)
- Evans, N. R., Carpenter, K., Robinson, R., Massa, D., Wahlgren, G., Vinko, J., and Szabados, L. Critical Complements: Progress on the Orbit of T Mon, IAU Coll 176,