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THE ASTRONOMER Electronic Circular No 2734      2011 Apr 26 14.04UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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V5588 SGR ( = NOVA SGR 2011 No. 2)
Further to the discovery announcement on TA E-Circular 2725, the object 
formerly referred to as Nova Sagittarii 2001 No. 2 has now been 
designated V5588 Sgr.

Rob Kaufman, Victoria, Australia has reported on April 25 that this nova 
may be re-brightening. He comments that on Mar 28 and Apr 8 it showed as 
a very faint dot and on Apr 13 nothing showed.  On Apr 24 the image 
looked stronger. In the green channel (normally corresponding fairly 
well to V-band), a mag 12.7 comp star is visible but a mag 13.2 comp 
star is not. See the following for the image:

http://i727.photobucket.com/albums/ww271/Rob_Kau/V5588Sgr24Apr2011comp.jp
g

U. Munari, Istituto Nazionale di Astrofisica, Padova Astronomical 
Observatory and others report on CBET 2707 that the nova is on a fast 
rise toward a bright second maximum, after the primary maximum that it 
reached on 2011 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 t2 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.

They add that it is too early to say if this will be a single secondary 
maximum like those displayed by V2491 Cyg, V1493 Aql and V2362 Cyg, or 
whether instead it will mark the beginning of an instability phase 
characterised 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 are markedly 
differ in spectral classification.

Guy M Hurst