Rare outburst of SW UMa


(vsnet-alert 386)

SW UMa is undergoing one of its rare outbursts as indicated by the following observations by L. T. Jensen (vsnet-obs 2562 message).

SW UMA     960411.847 14.0
SW UMA     960411.875 13.5
SW UMA     960411.955 11.7
SW UMA     960411.969 11.4, rapid rise to maximum

The outburst is apparently on its way to maximum. High-speed photometry is therefore highly encouraged, by taking the present first-ever opportunity to cover an entire (super)outburst of this unique dwarf nova. A systematic search for super-QPOs (QPOs with gingantic amplitudes, which probably appear only during the early stage of superoutbursts; cf. Kato et al. 1992 for this particular object: PASJ 44, L215) may be interesting.

SW UMa was last seen in outburst in Aug. 1993. We will keep readers informed via VSNET mailing lists and the VSNET Home Page.

Regards,
Taichi Kato

about TOADs

Historical outbursts of SW UMa

(vsnet-obs 2570, Taichi Kato)

  List of historical outbursts of SW UMa (AN 307 + new data)

      date         JD         observer
  1909 Mar 24                 Ceraski
  1937 Apr  7    2428631      Parenago,Zinner
  1939 Nov 17      29585      AAVSO
  1942 Jan 17      30377      AAVSO
  1943 Jul         30921?     Himpel
  1943 Dec 14      31073      AAVSO
  1945 Mar  7      31522      AAVSO, single obs. 12.5 mv
  1946 Feb  1      31853      AAVSO, single obs. 13.6 mv
  1947 Mar 12      32257      Beyer,Wellmann
  1947 Jul 21      32388      Beyer,Wellmann
  1948 Nov  5      32861      Beyer,Wellmann
  1950 May  9      33414      Beyer,Wellmann,Sonneberg
  1952 Mar 20      34092      Ashbrook,Beyer,Wellmann,Sonneberg
  1957 Apr  2      35931      Sonneberg (one day long at 12.4 mp)
  1960 Dec 12      37281      Sonneberg
  1965 Feb 15      38807      AAVSO,BAA,Sonneberg
  1968 Mar  4      39920      AAVSO (not fully confirmed)
  1969 Nov 20      40546      AAVSO
  1970 Feb  7      40625      AAVSO,Sonneberg
  1973 May 24      41831      AAVSO,AFOEV,Sonneberg
  1975 Sep 16      42672      AFOEV,Sonneberg
  1976 Nov 17      43100      AFOEV
  1977 Jan  8      43152      AFOEV, single obs. 12.2 mv
  1977 Dec 11      43489      AFOEV,Sonneberg
  1979 Feb 23      43928      AFOEV,Sonneberg
  1980 Jun 12      44403      AFOEV
  1981 Dec 21      44960      AFOEV,BAA,Sonneberg

  1986 Mar  3      46493      
  1990 Mar 14      47965      
  1991 Feb 25      48313      
  1992 Mar  3      48685      
  1993 Feb 17      49036      well-observed normal outburst
  1993 Aug 10      49210      

Detection of superhumps

(vsnet-obs 2651, Rudolf Novak)

Observer: Rudolf Novak
Telescope: Newton 40cm
Place: Copernicus Observatory Brno, Czech Republic
---------------------------------------------------

CCD R-band photometry of CVs SW UMa made on 17./18. 04. 1996 at Copernicus Observatory in Brno (Czech Republic) shows superhumps with period P=0.05866d and amplitude about 0.20mag. Error is around 0.04mag for each image. (We have also datas from 17. til 20. 04. 1996 but thay are not reduced yet.)

-------------------------------------------
   ..            .
   .     *        .                          .             *
                                          *       *
                   .                            Rudolf Novak    *       *
                                       Nicholas Copernicus Observatory
 *                                         .*    BRNO 616 00
                *                            * Czech Republic       .     *
              *                     *---------------------------------------*
           *  .                     e-mail:rudolfn@sci.muni.cz         .*
               .          *             .  rudolfn@monoceros.physics.muni.cz
\o/ <- It's me  .                      *   rudolfn@indus.physics.muni.cz
___________                         h-page:http://www.sci.muni.cz/~rudolfn
|_|_|_|_|_|   *                     *---------------------------------------*
          |                         Private:     Rudolf Novak
 -----    |     /  \           _ _ _      .*  Bohuslava Martinu 50         *.
 |-|-|    |     \  /          |-----|             BRNO 602 00          *.
 -----    |      ||           |-----|           Czech Republic
          |\__   || <- a tree |     |
__________|_||________________|_____|_\
    Our observatory... (c) RKN         \___________________________________ 

Present light curve

Light curves of previous outbursts (VSOLJ)

Recent light curve

The 1986 superoutburst

The 1990 superoutburst

The 2000 Superoutburst

The 2000 Superoutburst

Chart and sequence

(vsnet 614, Brian Skiff)

During the recent eruption of SW UMa, I was prompted to get photometry for some of the brighter stars in the field, selected from the (d)-scale AAVSO chart last revised March 1958. The AAVSO sequence has been long known to have inconsistencies (see Hornby 1975, JBAA 85,528).

I observed the stars on two nights (14 April and 1 May 1996 UT) using the Lowell 53cm photometric telescope with a 29-arcsec diaphragm and Stromgren b and y filters. The results for the standard stars are given below along with residuals from the assumed values. Primary standards are marked with an asterisk. The rms residuals are +/- 0.007 for V and +/- 0.004 in b-y. The results for the field stars are listed below. V magnitudes for two bright stars appearing on the chart are quoted from the literature, and for the faintest star, which is close to the dwarf nova, I give the results of Misselt (1996, PASP 108,146). I include the position for SW UMa also, since the one given on the AAVSO chart is in error.

Standard stars

Name          V (obs) b-y   n  resV  res(b-y)
HD 42049    5.930    1.049  1  -005   +005
HD 60803*   5.908    0.373  1  +005   -003
HD 64491*   6.234    0.200  1  +004   +004
HD 72779    6.582    0.434  1  +002   -006
HD 73665    6.381    0.600  2  -009   -003
HD 73666    6.616    0.003  2  +006   -002
BD+20 2161  8.815    0.194  2  +005   +002
HD 76151*   6.017    0.407  1  +009   -011
HD 81567    6.004    0.801  1  +007   -002
HD 85217*   6.230    0.308  2  -006   +003
HD 97907    5.317    0.750  1  +009   +001
HD100600*   5.940   -0.072  1  -008   -002
HD101606*   5.736    0.313  1  -009   +001
HD103095*   6.416    0.490  1  -011   +006
HD107168    6.246    0.088  1  -004   +007
HD110184    8.295    0.817  1  -002   -001
HD114092    6.178    0.849  2  +003   +001
HD115256    7.270    0.814  1  +005   -001


Photometry of stars in the field of SW Ursae Majoris

AAVSO  Name             RA  (2000)  Dec        V     b-y   n  spec
var   SW UMa          8 36 42.9  +53 28 37

 57   HD 73017                               5.66             G8IV    = HR3400

 65   HD 73131                               6.32             K0      = HR3405

 87   HD 72522        8 35 46.6  +53 43 33   7.901  0.657  2  K0
                                              .001   .006
 --   BD+54 1243      8 35 28.5  +53 42 20   9.576  0.842  2  (k3iii)
                                              .006   .007
100   BD+54 1242      8 34 53.1  +53 37 34   9.877  0.697  2  K2
                                              .008   .013
114   GSC 3797-1376   8 34 44.5  +53 20 05  10.984  0.582  2  (g8iii)
                                              .000   .008
114   GSC 3798-0705   8 36 20.8  +53 37 58  11.409  0.663  2  (k0iii)
                                              .014   .004
123   GSC 3798-0491   8 37 10.8  +53 30 00  12.142  0.608  2  (k0iii)
                                              .002   .007
130   GSC 3798-0530   8 35 58.2  +53 31 42  12.266  0.701  2  (k2iii)
                                              .001   .023
135   GSC 3798-0518   8 36 27.7  +53 17 52  13.51    ---      (k5iii)  (1)
                                              .03

Note:
(1)   V mag. from Misselt (1996, PASP 108,146).

Chartmakers should note in the same field the mag. 12.5 eclipsing variable star EQ UMa = GSC 3798-0625, at 8 36 27.2 +53 34 40 (2000), which was found by deYoung and Schmidt (1992, IBVS 3759). This is not one of the AAVSO sequence stars. Also, the very red mag. ~11 carbon star CGCS 2244 = GSC 3798-0518 = IRAS 08327+5328, at 8 36 27.7 +53 17 52, lies about 11' north of SW UMa. This star is likely to be at least somewhat variable.

\Brian Skiff (bas@lowell.edu)

Correction and addenda to SW UMa comparison stars

VSNET light curve (requires Java)

Light curve

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