First-ever observed outburst of LY Hya

(vsnet-alert 1707)

LY Hya appears to be in outburst. Confirmation is requested.

Visual observations

April 20   11:42UT   <14.8
April 22   10:56UT    14.4 seq: vsnet
           12:40UT    14.4

Rod Stubbings (VSS-RASNZ)
Drouin, Vic.

(vsnet-alert 1709)

Tried to confirm the outburst using a 0.25-m f/6.3 SCT & ST-7 CCD (unfiltered) at April 22, 1998 - 23h15m UT (object being extremely low above Belgian horizon). On the CCD image, I can see stars down to mag 15, but I could not detect a trace of LY Hya.

Can someone -located at a more favourable (= southern) location take a deeper image to get a definite answer ? Remember LY Hya is a very interesting object (see CVC 79 and also attached note of Taichi Kato).


Tonny Vanmunster relays in his CVC 79 (also vsnet-obs 2047) that LY Hya is being observed in outburst at V~14.4 by Steve Howell, who is performing infrared spectroscopy of CVs at Mauna Kea. Although this object has been suspected to be a dwarf nova, this is probably the first-ever recorded outburst. Further observations are emegerntly needed.

LY Hya, also called 1329-294, was originally discovered as a faint blue object near the famous spiral galaxy M83. This object soon turned to be a cataclysmic variable. Echevarria et al. 1983 (MNRAS 205, 559) obtained spectra which showed doubly peaked emission lines of Balmer and HeI, suggesting a high-inclination system.

Haefner et al. 1993 (Astrophys. and Space Sci. 204, 199) performed a radial velocity study, reporting the most probable orbital period of 0.13688 day. Their spectra showed very strong Balmer and HeI emission lines, whose equivalent widths suggest a dwarf nova with a low mass- transfer rate, rather than a nova-like system as initially thought.

More recent observations by Still et al. 1994 (NNRAS 267, 957) favored a solution of the system below the period gap. All these observations suggest that the object has been observed in quiescence, and that we may expect dwarf nova outbursts. Altough it is not still clear whether the present reported outburst is a normal or a super- outburst, the obser- vations by Howell seem to verify its suggested classification.

    133153.93  -294059.9    2000 LY Hya     UGSU:         (?)-17.4-18.4V
For observers' convenience, we have put VSNET charts with calibrated V-magnitude accesible via VSNET anonymous ftp or VSNET WWW Home Page.
   They may be found:, under pub/vsnet/DNe/LY_Hya : GIF files
   and (PostScript)

   WWW Home Page can be reached at
   (select "Topics & Alerts")

Taichi Kato

Confirmation by Nelson

(vsnet-alert 1713)

Confirmation of LY Hya outburst:

Date     UT      Mag (Vis)
980423  12:09    15.5
980423  13:33    15.5

vsnet seq
32cm Newtonian
Peter Nelson, Ellinbank, Australia

Detection of superhumps (Vrielmann)

(vsnet-alert 1722)

Dear Astronomers,

yesterday, 24th of April, during my observing run at the SAAO in South Africa I watched the fading LYHya for about 2 1/2 hours (UT 21:44 to 0:17) yesterday night and found nice Superhumps in the light curve confirming it to be an SU type dwarf nova. The humps have an amplitude of about 1mag in V and 0.5 mag in I.

Sonja Vrielmann.

 Dr. Sonja Vrielmann                                  *    *
  Dept. of Astronomy, University of Cape Town      *    *
  Private Bag, Rondebosch, 7700      Tel: +27-21-650-4042, Fax: -3352
 South Africa                       Email:

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