COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3172 Konkoly Observatory Budapest 31 March 1988 HU ISSN 0374-0676 PHOTOELECTRIC PHOTOMETRY OF RHO CASSIOPEIAE The peculiar variable star rho Cassiopeiae (rho Cas, HD 224014, = SAO 035879) was observed by four observatories using photoelectric photometers. Observations covered the period of time from September 18, 1986 to November 26, 1987. This represents a follow-up of data presented in an earlier bulletin (Leiker and Hoff, 1987). In that bulletin we reported on a substantial brightening of this star. That brightening epoch has now been confirmed by other observers, whose data is presented here. This note also contains data which suggests that the star has now began to dim slightly. rho Cas is a supergiant (F8pIA) star (Percy & Keith, 1985). rho Cas was discovered to be a variable in 1900 by Louise D. Wells (Pickering, 1901). Much of the time this star was confined to a brightness between 4.1m and 5.1m (Bailey, 1978). Between August 1945 and June 1947 rho Cas decreased in brightness more than a magnitude (Gaposchkin, 1949). After it recovered from this minimum, rho Cas continued its irregular variation in brightness of 4.1m and 5.1m (Leiker, 1987). rho Cas was observed extensively from June 1986 to April 1987 by Leiker and Hoff (1987). A 0.4 meter Cassegrain telescope and a STARLIGHT-1 photon counting photometer at the University of Northern Iowa (UNI) Hillside Observatory using standard B and V filters was used to make the observations. rho Cas was again observed by Leiker and Hoff from April 17, 1987 through August 19, 1987 using the same equipment. All of the Delta m are made in the sense of rho Cas - HD 223173. Table 1 lists the DeltaV magnitudes obtained from April 17, 1987 to August 19, 1987. Table 2 list the DeltaB- V magnitudes. Figures 1 and 2 are graphical representations of the data presented in Tables 1 and 2 respectively. Three observations were made to produce each of the delta magnitudes. Standard deviation and mean error were calculated according to Hall and Genet (1982). Nesbella and Gainer observed rho Cas from September 18, 1986 to October 19, 1987 using a 0.2 meter Schmidt-Cassegrain telescope and a solid state detector. rho Cas was observed in both blue and visual light. Also listed are the number of observations made to produce each delta magnitude. Standard deviation and mean error was calculated according to Hall and Genet (1982). Table 3 lists the DeltaV magnitudes and Table 4 lists the DeltaB-V magnitudes (Leiker, 1987). Figures 3 and 4 are graphical representations of the data presented in table 3 and 4 respectively. All of the Delta m are made in the the sense of rho Cas - HD 223173. Milton observed rho Cas from December 8, 1986 to November 26, 1987. Milton used a 0.2 meter Schmidt-Cassegrain telescope, and a 1 P21 photomultiplier tube with pulse counting electronics. The obtained delta m are in the sense of rho Cas - HD 223173 (Leiker, 1987). Standard deviation and mean error were calculated by Milton. Table 5 list the Delta magnitudes obtained. See figure 5. Pray observed rho Cas from September 10, 1986 to October 30, 1987. Mean error was calculated by Pray. Table 6 lists these data. The listed delta m are in the sense of rho Cas - HD 223173 (Leiker, 1987). Figure 6 is a graphical representation of this data. Table I. DeltaV magnitudes of rho Cas obtained by Leiker and Hoff HJD DeltaV sigma error 2446902.727 -1.085 0.044 0.025 2446930.853 -1.083 0.031 0.018 2446931.823 -1.029 0.015 0.009 2446932.821 -1.014 0.010 0.006 2446950.707 -0.983 0.020 0.012 2446951.691 -0.981 0.019 0.011 2446952.672 -0.952 0.022 0.013 2446953.697 -0.960 0.007 0.004 2446958.597 -0.970 0.018 0.011 2446958.741 -0.967 0.009 0.005 2446960.696 -1.007 0.023 0.013 2446961.709 -0.991 0.018 0.011 2446962.728 -1.006 0.003 0.001 2446972.734 -0.984 0.010 0.006 2446973.663 -0.970 0.007 0.004 2446978.680 -0.987 0.004 0.002 2446979.704 -0.990 0.045 0.026 2446979.713 -1.000 0.013 0.008 2446984.671 -1.009 0.018 0.010 2446990.654 -1.027 0.025 0.015 2446992.709 -1.038 0.006 0.003 2446993.676 -1.031 0.017 0.010 2446997.668 -1.060 0.042 0.024 2446998.708 -1.016 0.016 0.009 2447000.737 -1.046 0.041 0.024 2447002.656 -1.025 0.012 0.007 2447003.647 -1.015 0.007 0.004 2447005.697 -1.028 0.011 0.006 2447008.671 -1.036 0.004 0.002 2447010.661 -1.057 0.008 0.005 2447012.676 -1.047 0.005 0.003 2447024.597 -1.072 0.010 0.006 2447026.612 -1.083 0.013 0.007 [FIGURE 1] Figure 1. DeltaV magnitudes of rho Cas obtained by Leiker and Hoff Table II. Delta(B-V) magnitudes obtained by Leiker and Hoff HJD DeltaB-V sigma error 2446930.853 -0.205 0.044 0.031 2446931.823 -0.226 0.026 0.019 2446932.821 -0.228 0.022 0.016 2446950.707 -0.212 0.024 0.017 2446951.691 -0.197 0.022 0.015 2446952.672 -0.228 0.050 0.036 2446953.697 -0.206 0.026 0.018 2446958.597 -0.187 0.021 0.015 2446960.696 -0.170 0.032 0.022 2446961.709 -0.197 0.031 0.022 2446962.728 -0.172 0.003 0.002 2446972.734 -0.206 0.013 0.009 2446973.663 -0.210 0.029 0.020 2446979.713 -0.222 0.016 0.012 2446984.671 -0.192 0.024 0.017 2446990.654 -0.209 0.038 0.027 2446992.709 -0.173 0.006 0.004 2446993.676 -0.200 0.032 0.023 2446997.668 -0.170 0.047 0.033 2446998.708 -0.175 0.027 0.019 2447002.656 -0.199 0.016 0.011 2447003.647 -0.218 0.007 0.005 2447005.697 -0.206 0.014 0.010 2447008.671 -0.203 0.012 0.009 2447010.661 -0.202 0.009 0.007 2447012.676 -0.220 0.013 0.009 2447024.597 -0.220 0.015 0.011 2447026.612 -0.210 0.020 0.014 [FIGURE 2] Figure 2. Delta(B-V) magnitudes of rho Cas obtained by Leiker and Hoff Table III. DeltaV magnitudes of rho Cas by Nesbella and Gainer JD Delta m sigma error # 2446691.516 0.921 0.011 0.008 2 2446732.686 1.037 0.005 0.002 8 2446735.541 1.037 0.008 0.002 16 2446748.695 1.086 0.009 0.003 12 2446812.688 1.239 0.027 0.012 5 2446822.573 1.247 0.009 0.002 14 2446829.542 1.253 0.015 0.004 12 2446837.535 1.256 0.009 0.003 10 2446845.512 1.254 0.009 0.003 9 2446871.521 1.219 0.017 0.007 7 2446872.517 1.212 0.011 0.006 4 2446874.523 1.210 0.023 0.010 5 2446877.524 1.217 0.011 0.006 3 2446895.869 1.121 0.010 0.004 8 2446906.799 1.086 0.033 0.007 22 2446964.757 0.986 0.012 0.007 3 2446970.757 0.999 0.008 0.003 5 2446971.696 0.963 0.025 0.015 3 2447029.773 1.083 0.009 0.004 6 2447039.628 1.103 0.024 0.017 2 2447042.641 1.186 0.284 0.107 7 2447053.688 1.078 0.008 0.003 6 2447067.613 1.112 0.006 0.003 5 2447073.623 1.130 0.008 0.004 5 2447082.609 1.120 0.005 0.002 5 2447083.597 1.129 0.008 0.004 5 2447087.562 1.128 0.006 0.003 5 [FIGURE 3] Figure 3. DeltaV magnitudes of rho Cas obtained by Nesbella and Gainer Table IV. Delta(B-V) magnitudes of rho Cas by Nesbella and Gainer JD B-V sigma error 2446691.516 0.108 0.023 0.017 2446732.686 0.168 0.034 0.024 2446735.541 0.251 0.033 0.024 2446748.695 0.406 0.071 0.050 2446812.688 0.300 0.049 0.035 2446822.573 0.316 0.034 0.024 2446829.542 0.381 0.043 0.030 2446837.535 0.319 0.033 0.023 2446845.512 0.242 0.018 0.013 2446871.521 0.293 0.038 0.027 2446872.517 0.276 0.018 0.013 2446874.523 0.273 0.038 0.027 2446877.524 0.145 0.036 0.025 2446895.869 0.185 0.039 0.027 2446906.799 0.094 0.037 0.026 2446964.757 0.192 0.031 0.022 2446970.757 0.132 0.024 0.017 2446971.696 0.332 0.035 0.024 2447029.773 0.242 0.043 0.030 2447039.628 0.196 0.029 0.021 2447042.641 0.123 0.284 0.201 2447053.688 0.261 0.021 0.015 2447067.613 0.287 0.015 0.010 2447073.623 0.282 0.012 0.008 2447082.609 0.284 0.014 0.010 2447083.597 0.276 0.015 0.011 2447087.562 0.278 0.018 0.012 [FIGURE 4] Figure 4. Delta(B-V) magnitudes of rho Cas obtained by Nesbella and Gainer Table V. DeltaV magnitudes of rho Cas by Milton JD deltaV sigma error # 2446772.692 -1.126 0.005 0.003 3 2446792.792 -1.243 0.028 0.016 3 2446803.680 -1.247 0.004 0.002 3 2446811.637 -1.238 0.009 0.005 3 2446832.669 -1.263 0.013 0.008 3 2446845.681 -1.256 0.012 0.007 3 2446851.664 -1.253 0.010 0.006 3 2446987.880 -1.046 0.008 0.004 3 2447001.810 -1.044 0.007 0.004 3 2447015.735 -1.074 0.007 0.004 3 2447030.879 -1.102 0.004 0.002 3 2447037.782 -1.097 0.011 0.006 3 2447071.695 -1.138 0.007 0.004 3 2447085.689 -1.152 0.022 0.013 3 2447094.649 -1.148 0.004 0.002 3 2447102.690 -1.157 0.003 0.002 3 2447125.627 -1.118 0.002 0.001 3 [FIGURE 5] Figure 5. DeltaV magnitudes of rho Cas obtained by Milton [FIGURE 6] Figure 6. DeltaV magnitudes of rho Cas obtained by Pray Table VI. DeltaV magnitudes of rho Cas by Pray JD DeltaV error JD DeltaV error 2446683.5 -0.87 0.006 2446820.5 -1.21 0.006 2446691.5 -0.90 0.006 2446824.5 -1.22 0.006 2446709.5 -0.97 0.006 2446834.61 -1.23 0.006 2446715.5 -0.98 0.006 2446841.53 -1.22 0.006 2446723.5 -1.00 0.006 2446846.51 -1.22 0.006 2446732.5 -1.01 0.006 2446859.52 -1.18 0.006 2446747.5 -1.04 0.006 2446862.53 -1.17 0.006 2446754.5 -1.07 0.006 2447040.558 -1.06 0.002 2446760.5 -1.08 0.006 2447065.535 -1.09 0.002 2446764.5 -1.08 0.006 2447074.493 -1.10 0.002 2446770.5 -1.11 0.006 2447083.493 -1.10 0.002 2446786.5 -1.18 0.006 2447091.536 -1.12 0.002 2446792.5 -1.19 0.006 2447098.53 -1.11 0.002 2446809.5 -1.20 0.006 P. STEVEN LEIKER DARREL B. HOFF Hillside Observatory Department of Earth Science University of Northern Iowa Cedar Falls, Iowa 50614-0506 JOHN NESBELLA MICHAEL GAINER Department of Physics Saint Vincent College Latrobe, Pennsylvania 15650 RUSSELL MILTON Klamath Observatory Somes Bar, California 95568 USA DON PRAY Furnace Hill Observatory 40 Hillcrest Drive Cranston, Road Island 02920 USA References : Bailey, J. (1978). rho Cassiopeiae, 1964-1975. Journal of the British Astronomical Association. 88, (4), 397-401. [BIBCODE 1978JBAA...88..397B ] Gaposchkin, S. (1949). Rho Cassiopeiae. Harvard College Observatory Bulletin. Number 919, 18-19. [BIBCODE 1949BHarO.919...18G ] Hall, D. S., & Genet, R. M. (1982). Photoelectric Photometry of Variable Stars. International Amateur-Professional Photoelectric Photometry. Fairborn, OH: Fairborn Observatory. [BIBCODE 1982ppvs.book.....H ] Leiker, P. S., & Hoff, D. B. (1987). Photoelectric photometry of Rho Cassiopeiae. Information Bulletin on Variable Stars. Number 3020. Leiker, P. S. (1987). A Review of Photometric Research on rho Cassiopeiae. Including Unpublished Master's Thesis. University of Northern Iowa. Cedar Falls, Iowa, USA. Percy, J. R., & Keith, D. W. (1985). The quasi-cepheid nature of Rho Cassiopeiae. Madore, B. F. Cepheids: Theory and Observations. University of Cambridge Press. [BIBCODE 1985cto..conf...89P ] Pickering, E. C. (1901). Sixty-four new variable stars. Harvard College Observatory Circular. Number 54. [BIBCODE 1901AnHar..45....1P ]