Rare outburst of T Leo

(vsnet-alert 733)

The SU UMa-type dwarf nova T Leo is undergoing an outburst as reported by R. J. Modic (AAVSO) in [vsnet-obs 5104].

Object      YYMMDD.DDD(UT)      Mag   observer code
LEOT        970219.276         12.2   MRV
LEOT        970219.347         11.9   MRV

The last outburst of T Leo in the VSNET reports dates back to 1995 May 21, when the star showed a normal outburst reaching mv ~10.

Taichi Kato

(vsnet-alert 734)

T Leo appears to be in outburst.

T LEO      97 FEB 19.4889   10.9         HSG    Seq: AAVSO
T LEO      97 FEB 19.5000   10.9         HSG    
T LEO      97 FEB 19.5250   10.8         HSG  
T LEO      97 FEB 19.5486   10.7         HSG 
Confirmative observations would be very appreciated.


Gene Hanson

(vsnet-alert 738)

T Leo was actually last observed in outburst by P. Schmeer on 1995 Nov. 13 at mv=10.4 (cf. vsnet-alert 272). This outburst was confirmed to be a superoutburst (cf. vsnet-alert 279, L. Szentasko).

Taichi Kato

EUVE and RXTE observations


(vsnet-alert 746)

Observations to vsnet-obs indicate the dwarf nova T Leo is showing a remarkable re-brightening, a presumable superoutburst triggered by the 'precursor' outburst on Feb. 19. Selected observations since the decline of the first maximum:

   YYMMDD(UT)   mag    code
   970220.378   111    MRV
   970220.447   111    MRV
   970220.485   109    HSG
   970220.624   107    Wnt
   970220.717  11.25V  Kis
   970220.828  11.36V  Kis
   970221.198   118    MRV
   970221.485   118    HSG
   970221.708  <119    Wnt
   970222.239  <129    HSG
   970222.581  11.73V  Kis
   970222.635  <116    Wnt
   970222.678   109    Ioh
   970222.717  11.09V  Kis
   970223.180   108    MRV
   970223.241   107    MRV

V-band CCD observations by S. Kiyota (vsnet-obs 5127) indicate superhumps probably already appeared during the decline phase of the precursor outburst. The present behavior strong resembles that observed during the initial stage of the 1993 Jan. superoutburst (T. Kato, in preparation).

Taichi Kato

Previous observations

Light curve of the 1995 May normal outburst (courtesy by AFOEV and VSOLJ):

Light curve of the 1994 April superoutburst (courtesy by AFOEV and VSOLJ):

Superhumps (1993 Jan. superoutburst):


The 1993 superoutburst record

(vsnet-alert 747)

Extracted from old (pre-SN 1993J, pre-VSNET) log archive, recording the 1993 January superoutburst of T Leo. Hope this would be helpful in designing your crucial observations. We are happy to receive your report on successful observations, and far more productive exchange of information on this medium of 4-year's continuous upgrade! (Use vsnet-obs for reporting, vsnet-chat for discussion.) The VSNET manager group will be continuously upgrading the T Leo online information.

Taichi Kato

From: Patrick Schmeer
Date: 1993-01-04

Visual magnitude estimates by P. Schmeer, Bischmisheim, Germany:

Jan.  1.166 UT, (13.9 ;  2.124,  10.4 ;  3.119,  10.7 ;
      4.130 UT,  10.9
Rare outburst (cf. several IAUCs)

Patrick Schmeer

T Leonis

CCD observations of T Leo on Jan. 2 indicate this star was rapidly fading. The observations were performed from 2.750 to 2.895 UT with the time resolution of 30 s. The sky was very clear and I could cover more than two full orbital cycles of this dwarf nova with typical error of single observations less than 0.01 mag.

During this period, T Leo faded by 0.2 mag. Superimposed were hump features of 0.1 mag with maxima at 2.807 and 2.865 UT. The interval suggests this variation is not caused by superhumps, but by orbital modulation.

Subsequent observation tonight confirms rapid fading. The star looks at about V=11.8 on the TV monitor.

Taichi Kato

T Leonis

CCD photometry of T Leo was obtained on Jan. 3. Following preliminary results will be interesting to you.

  * The mean magnitude was V=11.6 (based on GSC V=11.9 star).
  * decline by 0.15 mag in 4 hr observation
  * Hump structures with an amplitude of 0.11 mag persisted.
    The hump maxima were seen at 3.762, 3.820, and 3.880 UT.
    The profile resembles superhumps (steeper rise).
  * The hump maxima are well represented by the following formula.
    Max UT = 2.806 + 0.05965 E
    The period is significantly longer (by 1.4%) than the orbital (0.058819)
    one, but is still different from the previously reported superhump
    period (0.06411).
Taichi Kato

From: Patrick Schmeer
Date: 1993-01-06 (updated on Jan. 6)

Visual magnitude estimates by P. Schmeer, Bischmisheim, Germany:

Jan.  1.166 UT, (13.9 ;  2.124,  10.4 ;  3.119,  10.7 ;
      4.130 UT,  10.9 ;  5.137,  10.5
Rather faint superoutburst.

T Leonis

Following preliminary results have been obtained from CCD photometry on Jan. 8. (Ouda station, 60-cm + CCD, V band)

  1) Continuatin of the outburst.
     The mean magnitude is steady at about V=11.0 (based om GSC V=11.9).

  2) Detection of definite superhumps.
    * Hump amplitude was 0.10 mag in V.  Steep rise and gradual decline.
      Secondary humps were not prominent.
    * Hump maxima occurred at 8.703, 8.769, 8.829, 8.894 UT.
      The times are well represented by the equation:
        Max.UT = 8.704 + 0.0633 E
      The period is 7.6% longer than the orbital one.  This period is
      close to that obtained during Jan. 1987 superoutburst (P=0.06411;
      Variable Star Bulletin, VSOLJ).  The present one is slightly shorter,
      but this difference is resonably explained by the fact that the present
      superoutburst is fainter than 1987 one.

  3) Connection with Jan. 5 hump features.
      Although cycle count is ambiguous because of 3-day gap and possible
      period change, the most probale periods are obtained assuming 45 or 44
      superhump cycles between 5.872UT and 8.704UT.
        Max.UT = 8.704 + 0.06289E (45 cycles)
        Max.UT = 8.702 + 0.06424E (44 cycles)
Taichi Kato

(note added in proof: later analysis has confirmed the period here was an 1-day alias of the true period).

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