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the second recorded outburst of ci aquilae was discovered in 2000 april by takamizawa since the first recorded outburst in 1917 .
after optical brightness reached its maximum , @xmath5 , in early may of 2000 , it rapidly decreased to @xmath6 in about 50 days .
a plateau phase follows ; the brightness leveled off at @xmath7 .
once it rapidly decayed to @xmath8 at the end of november of 2000 , it stayed at @xmath8 until march of 2001 .
ci aql has entered the final decline phase toward its quiescent level from may of 2001 as shown in fig .
1    we have modeled the system consisting of a massive white dwarf ( wd ) and a lobe - filling main - sequence ( ms ) star .
irradiation effects of the accretion disk ( acdk ) and the ms companion by the wd are included into the light curve calculation . the numerical method has been described in hachisu & kato ( 2001b ) .
we are able to reproduce the light curve by adopting model parameters similar to those of u sco ( hachisu et al .
2000 ) . the model parameters including those for the acdk are shown in fig . 1
( see also hachisu & kato 2001a ) .    after the paper of hachisu & kato ( 2001a ) has been published , we have new data on the final decay phase of the 2000 outburst ( schaefer 2001 , private communication ) and , now , are able to determine the turn - off time , the helium content of the envelope , and the duration of luminous supersoft x - ray phase as shown in fig .
1 . we have also revised the physical parameters : the unheated surface temperatures are @xmath9 k of the ms companion , @xmath10 k of the disk rim , the apparent distance modulus @xmath11 , the color excess @xmath12 , the absorption @xmath13 , and the distance to ci aql @xmath14 kpc .
the recurrent nova ci aquilae entered the final decline phase a bit before may of 2001 , showing the slowest evolution among the recurrent novae . 
 based on the optically thick wind mass - loss theory of the thermonuclear runaway model , we have estimated the turn - off time of the ci aql 2000 outburst in march of 2001 , after a supersoft x - ray source ( sss ) phase lasts 150 days from december of 2000 until may of 2001 . fitting our theoretical light curves with both the 1917 and 2000 outbursts 
 , we also obtained the wd mass to be @xmath0 , helium enrichment of ejecta , he / h@xmath1 by number , the mass of the hydrogen - rich envelope on the wd of @xmath2 at the optical maximum , which is indicating an average mass accretion rate of @xmath3 yr@xmath4 during the quiescent phase between the 1917 and 2000 outbursts .    
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