Electronic Telegram No. 502 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html RS OPHIUCHI A. Siviero and U. Munari, Istituto Nazionale di Astrofisica, Padova-Asiago, write that spectra (range 335-765 nm; dispersion 0.23 nm/pixel) of RS Oph were obtained on Apr. 22.04 UT with the 1.22-m telescope at Asiago. The spectra were fluxed into absolute units (erg/cm^2/s/A), to produce meaningful measured intensity ratios. The coronal emission lines are close to their maximum intensity, as happened similarly during the 1985 outburst at about 60-70 days past maximum. The strongest such lines are as follows, with the values in parentheses being the integrated flux with respect to that of H_beta, which itself is 4.0 x 10^(-11) erg/cm^2/s/A: [Ni XII] 423.0-nm (0.048), [Ar XIV] 441.3-nm (0.036), [Ni XIII] 511.6-nm (0.018), [Co XI] 516.8-nm (0.066), [Fe XIV] 530.3-nm (0.197), [Ar X] 553.3-nm (0.156), [Fe X] 637.5-nm (0.842), [Ar XI] 691.7-nm (0.074). Additional CCD magnitudes (cf. IAUC 8681, 8683): Feb. 28.48 UT, V = 8.07, B-V = +0.71, V-R_c = +2.40 (G. Sostero and E. Guido, remotely from near Mayhill, NM); Mar. 1.48, V = 8.03, B-V = +0.68 (Sostero and Guido); Mar. 3.47, V = 8.31, B-V = +0.60 (Sostero and Guido); Mar. 5.49, V = 8.44, B-V = +0.64, V-R_c = +2.40 (Sostero and Guido); Mar. 6.465, V = 8.53 (J. D. West, Mulvane, KS); 6.469, R = 6.52 (West); 6.475, I = 6.33 (West); Mar. 6.50, V = 8.41, B-V = +0.67, V-R_c = +2.31 (Sostero and Guido); Mar. 7.47, V = 8.63, B-V = +0.61, V-R_c = +2.46 (Sostero and Guido); Mar. 8.47, V = 8.66, B-V = +0.64, V-R_c = +2.46 (Sostero and Guido); Mar. 11.51, V = 8.70, B-V = +0.59 (Sostero and Guido); Mar. 12.48, V = 8.99, B-V = +0.70, V-R_c = +2.45 (Sostero and Guido); Mar. 13.48, V = 9.15, B-V = +0.62, V-R_c = +2.46 (Sostero and Guido); Mar. 14.47, V = 9.11, B-V = +0.67, V-R_c = +2.42 (Sostero and Guido); Mar. 16.47, V = 9.23, B-V = +0.67, V-R_c = +2.44 (Sostero and Guido); Mar. 21.48, V = 9.48, B-V = +0.62, V-R_c = +2.45 (Sostero and Guido); Mar. 23.47, V = 9.58, B-V = +0.72, V-R_c = +2.41 (Sostero and Guido); Mar. 24.48, V = 9.63, B-V = +0.73, V-R_c = +2.46 (Sostero and Guido); CCD magnitudes of RS Oph provided by E. Waagen, AAVSO (V-band magnitudes unless otherwise stated): Mar. 16.448 UT, 9.2 (R. James, Las Cruces, NM); 16.452, 9.172 (S. Dvorak, Clermont, FL); 22.438, 9.4 (James); 23.427, 9.5 (James); 24.429, 9.6 (James); 26.281, R = 8.15 (D. Mendicini, Santa Fe, Argentina); 26.421, 9.7 (James); 30.406, 9.8 (James); Apr. 2.398, 9.9 (James); 3.399, 9.9 (James); 4.391, 9.9 (James); 7.395, 10.0 (James); 13.374, 10.0 (James); 16.358, 10.1 (James); 26.332, 10.1 (James); 27.338, 10.2 (James); 29.331, 10.3 (James); May 2.321, 10.3 (James). Visual magnitude estimates (cf. IAUC 8688), provided in part by the AAVSO: Feb. 14.226 UT, 5.3 (M. Mario A. Fernandez Ocana, Vallirana, Spain); 15.214, 6.0 (Fernandez Ocana); 17.174, 6.4 (Fernandez Ocana); 17.249, 6.5 (C. Labordena, Castellon, Spain); 18.858, 6.8 (A. Pearce, Nedlands, W. Australia); 19.852, 7.2 (Pearce); 20.844, 7.2 (Pearce); 21.210, 7.1 (Fernandez Ocana); 21.847, 7.4 (Pearce); Mar. 16.315, 9.2 (J. Bortle, Stormville, NY); 17.163, 9.3 (B. Granslo, Fjellhamar, Norway); 17.361, 8.9 (M. Komorous, London, ON, Canada); 20.117, 9.3 (P. Dubovsky, Podbiel, Slovakia); 23.195, 9.4 (E. Muyllaert, Oostende, Belgium); 27.024, 9.5 (P. Reinhard, Vienna, Austria); Apr. 2.160, 10.1 (G. Poyner, Birmingham, England); 8.066, 9.5 (G. Mavrofridis, Nikea, Greece); 11.138, 10.0 (P. Cloesen, Beringen, Belgium); 21.102, 10.0 (A. Amorim, Florianopoulos, Brazil); 24.110, 10.0 (D. Storey, Douglas, Isle of Man, England); May 3.019, 10.1 (E. Van Ballegoij, Heesch, Netherlands). NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2006 CBAT 2006 May 4 (CBET 502) Daniel W. E. Green