About TOADs (from the VSNET log)

(vsnet-alert 127, 1995 May 3)

For the interest of any observers, I maintain an up to date list of confirmed and possible TOADs. This is available via email (request it from me at teh address below) or from my home page http://www.psi.edu/sbhgen.html

For example V795 Cyg is on this list and either a minimum magnitude or an orbital period will help confirm its TOAD status. Many such stars exist and only knowing both the orbital period (available roughly from superhump observations at maximum) and minimum magnitude will allow proper elimination or confirmation.


 Steve B. Howell 
 Planetary Science Institute, Astrophysics Group 
 620 N. 6th Ave. 
 Tucson, AZ 85705  USA 
 Phone (520) 622-6300 
 Fax (520) 622-8060 
 e-mail: howell@frankenstein.psi.edu
 homepage: http://www.psi.edu/

"trouble in the jungle" (Patterson)

(vsnet-alert 130, 1995 May 3)

There has been much mention of "TOADs" in this forum, and I thought it was worth entering a dissent on this term -- which it seems to me is astronomically and zoologically poor. Dwarf nova fans are familiar with the term "SU UMa stars", and the meaning is clear: dwarf novae whose eruptions divide very distinctly into long and short, and which show superhumps in their long eruptions. Some people also use the term "WZ Sge stars" to refer to the subset of SU UMas which either: (a) show the longest outburst intervals, (b) have few or no short outbursts, or (c) qualify according to both (a) and (b). Because this is somewhat vague, and because Nature provides no dividing line, many of us either do not use the term "WZ Sge stars" or use it only as a convenient shorthand for a more cumbersome phrase - "the most infrequently erupting SU UMa stars". At least it refers to an actual star; whether it is a useful subclass is harder to say.

Now comes this term TOADs. To my mind this has no meaning, at least none which bears any relation to the groupings suggested by Nature or physics. Outburst amplitudes of dwarf novae range smoothly from 2 to 9 mag with no breaks or suggestions of any dichotomy. Nor is there any distinction in the physics known, suspected, or alleged to be involved in the outburst -- they all seem to be powered by gravitational energy released by unstable mass flows through the accretion disk. Most stars receiving this label are WZ Sge stars, which are in turn basically just SU UMa stars which don't erupt much. Most SU UMas are intrinsically faint in quiescence and therefore have fairly large outburst amplitudes -- and the more intrinsically faint, the lower the accretion rate and hence the longer the outburst interval (as predicted in standard accretion disk theory). In all such properties the SU UMas form a smooth continuum, not suggestive of even an OBSERVATIONAL dichotomy, much less any true distinction in the underlying physics.

I strongly urge use of traditional variable-star nomenclature, lest we dissipate much energy trying to understand each other's favorite animal acronyms. "SU UMa stars" with the optional subclass "WZ Sge" seems like the best way to go.

TOADs, in this context, are also an offense against zoology. Toads move forward by a series of very short hops, whereas FROGS leap. But stars like WZ Sge and AL Com are distinguished for their leaps, and for having few or no short hops. Thus if we want a name from the animal kingdom, we might consider Fabulously Robust Outbursting Gravity-powered Stars.

But anyone who does so should be shot at sunrise.

joe patterson

Physics of TOADs

(snet-alert 131, 1995 May 3)


Just to point out that your email about TOADs, while informative, did indeed have a few likely errors.

The TOADs are indeed object which MUST have different physics in their outburst mechanisms (see Howell et al ApJ 1995, 439, 337 and other model calcs by John Cannizzo). whether this 'change' in outburst physics difference happens JUST at 6 mags or not is indeed not known, but it is NOT needed at 5 mags and IS needed at 7-10 mags.

Also, the TOAds are NOT just like SU UMa stars with bigger outbursts, The types of outburst (ie, shape and length and frequency) are different, The TOADs show large velocity winds at maximum , and there appears to be both superoutbursts and intermediate outbursts, as well as rare normal outbursts in soem TOADs.

as for the name not relating to the actual animal representation, I believe we could name hundreds and hundreds of cases where acyronyms do not relate to the item they are representing.

So I think it is NOT fair to simply dismiss TOADs nor place them into the bin of "just non-typical SU UMa stars"

Steve Howell

Some observations

WZ Sge-type candidates

(complied by T. Kato, vsnet 206)

Properties of possible, probable and certain WZ Sge-type Dwarf Novae

   Star     Max    Min  Amplitude    Orbital     
                          (mag)    Period (min)  
WZ Sge      7.0   15.5     8.5         81        
AL Com     12.8   20.5     7.7         81        
HV Vir     11.5   19.2     7.7         82        
WX Cet      9.3   18.0     8.7      69-85**      
VY Aqr      9.0   17.5     8.5         91*       
BC UMa     10.9   18.3     7.4         91**      
RZ Leo     12.3   19.3     7.0        102*       
V1251 Cyg  12.5   19:      6.5:       109**      
UZ Boo     11.5   20.5     9.0                   
V358 Lyr   13.2  [20      >6.8                   
AO Oct     13.5   21       7.5:                  
V551 Sgr   13.5   20       6.5:                  
GO Com     13.1   20:      7:                    
LS And     11.7   20.5     8.8                   
PQ And     10.0   18.8     8.8                   
KX Aql     11.5   17.5:    6.0:                  
SV Ari     12     22      10                     
BC Cas     10.7   17.4     6.7                   
EG Cnc     11.9   18.0     6.1                   
DV Dra     15.0  [21      >6                     
V592 Her   12.3   21.5:    9.2:                  
V632 Her   15.4   21       5.6:                  
GW Lib      9.0   18.5     9.5                   
V369 Lyr   15.2  [20.0    >4.8                   
GR Ori     11.5  [21      >9.5                   
N1990 Sgr   8.0   16.3     8.3                   
UW Tri     15    [21      >6                     
-- For     12.7  [19      >6.3                   
GD552             17.4                103        

 ** superhump period
 * orbital period estimated from quiescent light variation

TOADs and SXTs (Kuulkers and Howell)

PostScript file

International TOAD Watch

Discussions concerning EG Cnc outbursts

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