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Special Notice #45: 1804-18 V5558 Sgr = Nova Sgr 2007

April 24, 2007

Coordinates: R.A. = 18h 10m 18.27s Decl. = -18o 46' 52.1" (2000.0)

Further to AAVSO Special Notice #44, 1804-18 Nova Sgr 2007 has been given the name V5558 Sgr by N. N. Samus, Institute of Astronomy, Russian Academy of Sciences, according to IAU Circular 8832 (Daniel W. E. Green, ed.).

Spectroscopic information available to date and announced in Central Bureau Electronic Telegram 934 (Daniel W. E. Green, ed.) indicates that the exact nature of V5558 Sgr is not clear. T. Iijima, Astronomical Observatory of Padova, Asiago, reports that medium-dispersion spectra taken on Apr. 20.12 and 20.14 UT indicate that "this object could be a rather peculiar classical nova in the pre-maximum stage." H. Naito and K. Matsuda, Nishi-Harima Astronomical Observatory, and H. Yamaoka, Kyushu University, report that a low-resolution spectrum obtained on Apr. 20.80 UT suggest that "our view of the nova suffers some reddening. The overall feature of the spectrum does not resemble that of a classical nova, but with the amplitude (> 10 mag) of outburst and the absence of a pre-outburst counterpart in the infrared or x-ray regions, it could be very remarkable object."

Recent observations reported to the AAVSO include:
Apr. 21.1042 UT, 9.9, W. Kriebel, Schierling/Walkenstetten, Germany;
21.1306, 9.6, M. Jacquesson, Sevigny-Waleppe, France;
21.1360, 9.9, P. Schmeer, Bischmisheim, Germany;
21.196, 10.0. A. Amorim, Florianopolis, Brazil (via CBET 934);
21.3236, 9.6, L. Shotter, Uniontown, PA;
22.0764, 9.8, S. Swierczynski, Dobczyce, Poland;
22.1174, 9.7, Jacquesson;
22.1350, 10.0, Schmeer;
22.2889, 9.8, M. Komorous, London, Ontario, Canada;
22.3563, 9.6, Shotter;
23.0625, 9.6, Swierczynski;
23.0917, 9.7, Kriebel;
23.1310, 10.0, Schmeer;
24.3451, 9.8, Komorous;
24.4020, 9.7, R. Campbell, Largo, FL;

As mentioned in Special Notice #44, a chart of the region may be drawn using the coordinates above and VSP:

obsolete link: [http://www.aavso.org/observing/charts/vsp/]

2016 link: https://www.aavso.org/vsp

Sequence and calibration work on this field continue.

Please continue to observe this extremely interesting object, and report observations to the AAVSO as 1804-18 V5558 SGR. Be sure to include your comparison star information.

Thank you and good observing!

This special notice was compiled by: Elizabeth O. Waagen

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