COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 4019 Konkoly Observatory Budapest 5 May 1994 HU ISSN 0374 - 0676 OBSERVATIONS OF A SYMBIOTIC NOVA IN SAGITTARIUS This object was discovered by Minoru Wakuda on March 14, 1994, as a star of 10.7m and announced as a peculiar variable (Hirayama 1994). The position is alpha=18h51m43s delta=-19d45.9' (1950.0). The star has already been bright since 1993 March 29, but was fainter than 12.5m throughout 1992. Spectroscopic observations were carried out on 1994 March 30.4 (UT) with the ESO/MPI 2.2m-telescope and EFOSC-II. A low resolution spectrum (Fig. 1, resolution 0.84 nm) shows emission lines of Halpha, Hbeta and the infrared Ca II triplet, superimposed on a somewhat veiled late-K-giant continuum. A high-resolution spectrum (Fig. 2, resolution 0.19 nm) shows the Ca II H and K lines in absorption, as well as narrow emission lines of Hbeta and Fe II. The absence of blueshifted absorption lines, the narrowness of the emission lines (FWHM < 250 km/s), as well as the long standstill at maximum magnitude excludes the classification as a classical nova. The blue emission line spectrum resembles that of the symbiotic nova PU Vul in 1987-1988, eight years after brightness rise (Iijima 1989). On 21 plates of the Sonneberg astrograph 400/1600 mm, taken between 1984 and 1988, as well as on the last available sky patrol plate of this area, taken in 1990, the object is invisible. The data are as follows: JD 244... m_pg JD 244... m_pg JD 244... m_pg JD 244... m_pg 5912.43 [16.5 7039.32 [15.5 7088.24 [16.5 7387.39 [17 6232.52 [16.5 7039.33 [15.5 7088.25 [16.5 7404.32 [17 6264.46 [15 7063.30 [16.5 7353.43 [16.5 7404.33 [17 6287.38 [17 7063.31 [16.5 7353.44 [17 8069.49 [12 6287.39 [16.5 7087.24 [16.5 7355.34 [17 6298.39 [16.5 7087.25 [16.5 7387.38 [17 On 667 additional plates of the Sonneberg sky patrol with plate limits of about 12...14, taken in 1926...1948 and 1950...1983, the object is also always invisible. Similar results, based on 272 Harvard plates for the interval 1888...1989, are reported by Hazen (1994). A direct CCD frame taken at outburst (Fig. 3) was compared with the ESO/SERC Atlas J and R film copies. The outburst image lies in an empty field, ~ 3" north of the connecting line of two stars of about 20m, whose separation is ~ 5". Thus the preoutburst magnitude was below the limit of both plates, i.e. below m_V ~ 21.5, indicating an outburst amplitude of more than 11m. This is unusually large for a symbiotic nova; until now the poorly known object V2110 Oph = AS 239 held the record with 8m, while RR Tel has an amplitude of about 7.5m (Allen 1978,1984; Duerbeck 1987). [FIGURE 1] Figure 1. Low-resolution spectrum of the symbiotic nova, taken 1994 March 30.4 with EFOSC-II and grism 1 at the ESO/MPI 2.2m-telescope. Besides Halpha and Hbeta, the infrared Ca II triplet at 8498, 8542 and 8662 A is present at weak emission, while the Ca II H+K lines appear in absorption. The features in the continuum mimic a late K giant spectrum, but show low contrast, possibly being veiled by a featureless continuum. [FIGURE 2] Figure 2. Medium-resolution blue spectrum of the symbiotic nova, taken 1994 March 30.4 with EFOSC-II and grism 3 at the ESO/MPI 2.2m-telescope. The Ca II H+K lines appear in absorption. Hbeta is seen in emission. The lines at 4925, 5021, 5071, 5199, 5235, 5282, 5315 and 5365 A belong to the Fe II multiplets 41, 42, 48 and 49. [FIGURE 3] Figure 3. The field of Wakuda's symbiotic nova, observed 1994 March 30.4 with EFOSC-II at the ESO/MPI 2.2m-telescope. The field is 4.3' x 4.3', and the object is the bright star at the center. North is on the top, east to the left. With galactic coordinates l = 15d56, b = -9d53, the variable lies in field No.158 of Neckel's (1967) survey of galactic absorption, where A_V at large distances is typically 1m. Assuming Eddington luminosity for a medium mass white dwarf at outburst, M_V ~ 6 (Kenyon and Truran 1983), its distance is about 10 kpc, and with a z-distance of 1700 pc, it appears to be a bulge object. There is one caveat, however: The absolute magnitude of its progenitor, M_V, is fainter than 5m, and excludes any late type giant companion. Assuming an M-type giant companion would lead to unusually large distances and outburst luminosities. A ROSAT pointed observation carried out on 1992 Oct. 13/14 includes the field of the variable. No X-ray source was found, giving an upper limit of 0.004 cts/s. Assuming a 10^7 K blackbody emission (resp., bremsstrahlung spectrum) with A_V=1, this corresponds to 4x10^-13 erg cm^-2 s^-1 and 8x10^-14 erg cm^-2 s^-1, respectively. Monitoring of the ongoing outburst is encouraged. Acknowledgements. E.K.G. thanks Prof. Dr. H. Elsasser (MPIA Heidelberg) for granting observing time at the 2.2m telescope at ESO/La Silla. The work of G.A.R. has been supported by funds of the German Bundesministerium fur Forschung und Technologie under contract no. 05 2S0524 (7). We thank Dr. A. Pauldrach for permission to use his ROSAT observation, and Dipl.-Phys. R. Budell (AI Munster) for assistance with the identification. EVA K. GREBEL JOCHEN GREINER Sternwarte der Universitat Bonn MPI fur Extraterrestrische Physik Auf dem Hugel 71 D-85740 Garching, Germany D-53121 Bonn, Germany GEROLD A. RICHTER HILMAR W. DUERBECK Sternwarte Sonneberg Astronomisches Institut der Sternwartestr.32 Universitat Munster D-96515 Sonneberg, Germany Wilhelm-Klemm-Str.10 D-48149 Munster, Germany References: Allen, D.A., 1978, IBVS, No. 1399 Allen, D.A., 1984, Proc. Astr. Soc. Austr., 5, 369 [BIBCODE 1984PASAu...5..369A ] Duerbeck, H.W., 1987, Space Sci. Rev., 45, 1 [BIBCODE 1987SSRv...45....1D ] Hazen, M.L., 1994, IAU Circ., No. 5976 [BIBCODE 1994IAUC.5976....2H ] Hirayama, T., 1994, IAU Circ., No. 5961 [BIBCODE 1994IAUC.5961....2H ] Iijima, T., 1989, A&A, 215, 57 [BIBCODE 1989A&A...215...57I ] Kenyon, S.J., Truran, J.W., 1983, ApJ, 273, 280 [BIBCODE 1983ApJ...273..280K ] Neckel, Th. 1967, Veroff. Landessternw. Heidelberg, 19 [BIBCODE 1967VeHei..19.....N ]