[vsnet-chat 815] Nova Sgr 1998 oscillations

[Taichi Kato <tkato>]

Nova Sgr 1998 oscillations

   Using 60 visual and V-band estimates between Mar. 24 and Apr. 8 (all
are well-calibrated using suitable H/T sequence; GSC mags fortunately very
close to this system), I have determined the mean decline rate as
0.092 mag/day for these 15 days.  The nova class may be "moderately fast".

   Superimposed on this decline, oscillations up to 1 magnitude were
observed.  Distinct peaks around Mar. 26-27 and Apr. 3-4.

Table 1.  Nightly averaged magnitudes.

     mid-UT     mean   S.D.   N
 -----------------------------------------
   980324.586   8.163 0.204   5 all
   980325.569   8.074 0.197  10 all
   980326.349   8.326 0.149   3 all
   980327.488   8.259 0.156   3 all
   980328.793   8.693 0.135   4 all
   980329.647   9.095 0.162   3 all
   980330.343   9.006 0.146   7 all
   980401.394   8.977 0.240   4 all
   980402.719   9.235 0.241   4 all
   980403.723   8.914 0.128   5 all
   980404.495   8.938 0.184   4 all
   980405.579   9.331 0.236   4 all
   980406.203   9.700 0.000   1 all
   980407.750   9.400 0.000   1 all
   980408.123   9.200 0.000   2 all

   PDM analysis has yielded several candidate periods, of which 7-day
periodicity looks likely.  Longer periods, as suggested above, need to
be confirmed more long-baseline observations.

   The existence of relatively large-amplitude oscillations with a period
of an order of ~10 days may suggest similarity to V443 Sct (Nova Sct 1989)
and V4361 Sgr (Nova Sgr 1996).

Regards,
Taichi Kato

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