Electronic Telegram No. 2707
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


V5588 SAGITTARII
     U. Munari, Istituto Nazionale di Astrofisica, Padova Astronomical
Observatory; and S. Dallaporta and G. L. Righetti, ANS ("Asiago Novae and
Symbiotic stars") collaboration, write:  "V5588 Sgr (= Nova Sgr 2011 No. 2;
cf. IAUC 9203) is on a fast rise toward a bright second maximum, after the
primary maximum that it reached on Apr. 7 at B = 13.19, V = 11.30, R_c = 9.95,
and I_c = 9.08.  After a smooth decline that took the nova past t_2 (the
time required to decline two magnitudes from maximum) to B = 15.18, V = 13.70,
R_c = 11.04 and I_c = 10.75 on Apr. 20, a rapid rise in brightness has begun.
The nova on Apr. 25.11 UT was at B = 13.70, V = 11.70, R_c = 10.25, and I_c =
9.30 -- still on the rise and approaching the brightness of the first maximum.
It is too early to say if this will be a single secondary maximum like those
displayed by V2491 Cyg (Nova Cyg 2008 No. 2; Munari et al. 2011, New Astronomy
16, 209), V1493 Aql (Nova Aql 1999 No. 1), and V2362 Cyg (Nova Cyg 2006;
Munari et al. 2008, A.Ap. 492, 145), or whether instead it will mark the
beginning of an instability phase characterized by a series of re-brightening
and fading.  In the meantime, it is interesting to note that the time interval
between the first and secondary maxima were 15, 45, and 240 days for V2491
Cyg, V1493 Aql, and V2362 Cyg, respectively.  The 18-day interval between the
first maximum of V5588 Sgr on 2011 Apr. 7 and the current second maximum
would place V5588 Sgr close to V2491 Cyg, even if the two markedly differ in
spectral classification (Fe II-type for V5588 Sgr, He/N-type for V2491 Cyg)
and velocity of the ejecta (FWHM of emission lines 900 km/s for V5588 Sgr,
4000 km/s for V2491 Cyg."


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2011 CBAT
2011 April 25                    (CBET 2707)              Daniel W. E. Green