[vsnet-chat 152] More about Nova Sgr 1990

[Taichi Kato <tkato>]

Comment to Bruce Sumner's [vsnet-chat 148]:

   IAUC No. 5006 (1990 May 4) reported T. Harrison's infrared and McNaught's
photometry.  The photometric record thus becomes:

   1990 Feb 20.4   <11   (Liller, orange filter, IAUC 4974)
            23.4     8.0 (Liller)
            24.3     8.9 (Liller)
        Mar  2.4     9.8 (Liller)
             9.7   J=10.13, H=9.87, K=9.24 (Harrison, IAUC 5006)
            10.7   J=10.36, H=10.04, K=9.48
            13.7   J=11.78, H=11.39, K=10.91, L=9.97
            24.67    14  (McNaught, IAUC 5006)

   R. M. Wagner reported in IAUC No. 5008 (1990 May 9) spectroscopy on
May 6.42.  The spectra showed emission lines of H-alpha, H-beta, HeI, HeII
and CIII/NIII.  The FWHM of H-alpha was reported to be ~400 km/m.  Wagner
concluded from these findings and the absence of forbidden lines that this
object is probably a dwarf nova like WZ Sge.

   My own visual observations from the VSOLJ record:

    date UT    mag  observer
 -----------------------------
  900309.795   115  Kat
  900309.835   116  Kat
  900310.837   118  Kat
  900312.810   120  Kat
  900313.799   124: Kat
  900313.816   124  Kat
  900313.838   124  Kat
  900313.844   124  Kat
  900315.831   125: Kat
  900316.808   131: Kat
  900316.837   131: Kat
  900321.808   131: Kat
  900321.840   131: Kat
  900325.822   133: Kat
  900326.808   135: Kat
  900402.801  <140  Kat
  900404.796  <131  Kat
  900405.757  <135  Kat
  900406.797  <136  Kat
  900418.686  <135  Kat
  900424.751  <135  Kat
  900505.766  <140  Kat

   Due to the lack of a good finding chart (and sequence) in this crowded
area, estimates below mag 12 are extremely uncertain.  The situation was
improved after I began using the GSC in April.

   From Harisson's infrared observations, there probably existed a sudden
drop around March 13.  A duration of ~18 days for the 'bright' state
may be comparable to those of WZ Sge stars (~20 days in AL Com and EG Cnc
before sharp declines).  However, a large reddening (A_V ~ 3 mag or more)
inferred from Harrison's infrared colors (assuming typical dwarf nova
colors), also inferred from the existence of interstellar Na D lines (Wagner,
IAUC 5008), seems to me rather difficult to reconcile with the dwarf nova
classification (and the blue quiescent counterpart suggested by Bruce Sumner,
vsnet-chat 148), since all these constraints should require the object
very close to us (reaching V ~5! at maximum without interstellar extinction)
and at the same time highly reddened.

Regards,
Taichi Kato

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