, so
why not post your Diskobolos article to vsnet-chat? I would like to
read it please....
Dear colleagues,
I have one question about strange behavior of EG Cnc. Can someone help me? I would like to ask you, if some star before EG Cnc showed this unusual light curve or if EG is first one. And of course can we explain it? Right now I don't have any idea how to. I am preparing a few sentences to our magazine Diskobolos and would know some opinions. I am looking forward to receive some answers thank you very much and have a nice dreams
Rudolf *************************************************************************** * Rudolf Novak Private: Rudolf Novak * * Nicholas Copernicus Observatory Bohuslava Martinu 50 * * Kravi Hora 2 BRNO 602 00 * * BRNO 616 00 Czech Republic * * Czech Republic * *************************************************************************** * e-mail: rudolfn@physics.muni.cz * * h-page: http://www.sci.muni.cz/~rudolfn * *************************************************************************** * " ... no, There's no dark side of the Moon ... " * ***************************************************************************
I believe UZ Boo showed two minor brightenings after its spectacular superoutburst in 1994. Though there is no particular VSNET WWW page on this phenomenon, you may trace it in the corresponding VSNET log and the light curve archive
Also, looking forward to reading some of your Diskobolos articles in this chat list (if you please).
Regards,
Taichi Kato
Regarding mutiple maxima of dwarf novae, T Leo is probably the best known. This star show triple maxima at least two times. Even before I started my career of variable star observing, I had been notified by one of my variable star friends that T Leo is famous for its double maxima -- but I failed to look back the corresponding record in literatures. Someone knows?
* * *
I can vividly remember my first sighting of the T Leo outburst in 1987 January -- how bright the star looked against that particularly sparse field! I then tried to detect superhumps by eye, standing several hours in the snow, my colleague S. Fujino secured photographic observations. Without this outburst, I might not have chosen a way to an astronomer.
Regards,
Taichi Kato
UZ Boo did indeed show two post outburst brightenings in 1994. AL Com displayed a nice dip, followed by a post outburst brightening in 1995, (as did V1028 Cyg in 1995) and GO Com showed unusual behaviour in 1995 with a trigger(?) outburst, followed by a superoutburst and post outburst brightening (it seems 1995 was a good year for this). The light curve for EG Cnc is however the most spectacular I have ever seen, especially for a star which has been inactive (or so we think) for so long.
Increased monitoring of these fascinating objects by amateurs over the past few years have increased our awareness of this type of phenomenon.
Gary Poyner
UZ Boo showed indeed 2 shorter maxima or rebrightenings after its main superoutburst. You can have a look at http://www-astro.physics.ox.ac.uk/~erik/egcnc.html, and our comments in vsnet-alert 654.
Regards,
Erik Kuulkers
> GO Com showed unusual behaviour in 1995 with a trigger(?) outburst, followed > by a superoutburst and post outburst brightening (it seems 1995 was a good > year for this).
Yes, indeed! Interested should please have a look at this exciting story at http://www.kusastro.kyoto-u.ac.jp/vsnet/DNe/gocom.html. Triple outbursts of GO Com, T Leo and V1028 Cyg seem to slightly differ from that of UZ Boo (and of course EG Cnc) in that outburst complexes of the former class seem to be composed of a triggering normal outburst + superoutburst followed by a post-outburst brightening, whereas those in UZ Boo and EG Cnc are composed of a superoutburyrst and a sequence of normal (short) outbursts.
Regards,
Taichi Kato
The superoutbursts of normal SU UMa stars, such as VW Hyi, have been shown to be triggered by a normal outburst as well. These normal SU UMa stars have also regular normal outbursts in between their superoutbursts. In that respect it might be different to the so-called TOADs or WZ Sge stars, which have not yet shown to be triggered by a normal outburst, and show (almost) no normal outburst in between superoutbursts (with very long recurrence times), except just after the outburst, such as indeed EG Cnc and UZ Boo.
Erik Kuulkers
dear vsnet readers, as to the question posed by Rudolf, please refer to the ApJ paper by Kuulkers et al. in the 1996 May ApJ Letters, 462, L87. All is revealed there.
Cheers, Steve
I believe V1028 Cyg has an outburst amplitude exceeding 6 magnitude based on the recent quiescent estimate. Doesn't it well deserve a TOAD? Or should we modify slightly the TOAD definition?
It's indeed interesting that there is yet no observational hint of triggering normal outburst even in well-observed WZ Sge-type superoutbursts.
Regards,
Taichi Kato
Defining a SU UMa star as a TOAD (or, equivalently, a WZ Sge star) SOLELY basing it on outburst magnitude is not the right way to classify it as a TOAD. In addition the star should exhibit long intervals between superoutbursts (years to decades) with almost no normal outbursts. Note that this does not imply that the TOADs should be regarded as a completely new CV-group. They are most probably the extreme end of normal SU UMa stars.
The bright superoutburst and subsequent rebrightenings in V1028 Cyg occurred after a long quiescent period and may in this respect resemble TOADs. However, this star also show periods of regular normal and superoutburst behaviour. V1028 Cyg, and a similar system, SW UMa, may be the bridge between normal SU UMa's and TOADs.
Erik Kuulkers
Eric Kuulkers wrote: > Defining a SU UMa star as a TOAD (or, equivalently, a WZ Sge star) SOLELY > basing it on outburst magnitude is not the right way to classify it as a > TOAD. In addition the star should exhibit long intervals between > superoutbursts (years to decades) with almost no normal outbursts.It's rather new to me since I have been taught TOADs are defined by their amplitudes -- others like the outburst behavior or the SU UMa-nature are frequently met characterstics of this group, and not a part of the definition. Or is the term "TOAD" a synonym for the long-used "WZ Sge star"?
> The bright superoutburst and subsequent rebrightenings in V1028 Cyg > occurred after a long quiescent period and may in this respect resemble > TOADs. However, this star also show periods of regular normal and > superoutburst behaviour.
The outburst pattern of V1028 Cyg does not seem to be so regular. Intervals between superoutbursts ranged between one and three years -- quite similar to SW UMa as Kuulkers already pointed out.
> V1028 Cyg, and a similar system, SW UMa, may be the bridge between > normal SU UMa's and TOADs.
I generally agree in this point. There seems to be a continuous transition between "classcal" SU UMa stars and WZ Sge stars (or TOADs, if I understand the definition correctly) in many points, but the existence of "early" or "orbital" superhumps and the apparent lack of triggering normal outbursts seem to be unique to the latter extreme end.
Regards,
Taichi Kato
G'day Rudolf,
Hypothesis to explain EG Cnc: it's being attacked by aliens ;)
I would have liked to observe this one for myself, but looking through the top of Adelaide's skyglow at 13th mag stars is a bit difficult for me. However, there seems to be a similar star in the other direction where my sky is dark - WX Hydri.
The VSS RASNZ Circulars for October & November arrived this week. Here's some more information about that odd superoutburst of WX Hyi:
JD of maximum 2450000+ duration (rise-peak-fall) days magnitude ----------- ------------------------------ --------- 363 2.9 - 5.0 - 5.7 (supermax) 12.0 380 1.1 - - 0.9 12.5 386 1.4 - 0.7 - 1.0 12.5 394 1.2 - 0.2 - 2.3 12.4 406 2.0 - - 1. 12.8 416 (Nov 28) 1.8 - 1. - 1.1 12.0 And some dates from my own notes for 1996 December: outburst - 10th(?) no outburst - 12th, 30th, 31st
How many of those maxima represent re-brightenings of a superoutburst? Maybe all of them? WX Hyi certainly didn't "slow down" after the superoutburst like many other UGSS's would have! In fact it may be even more active than indicated; there has been a lot of cloudy weather in the Southern Hemisphere lately.
WX Hyi's frequency of outburst was about 2 or 3 times per month a few years ago, and outbursts were typically less than 2 days long. Even its superoutbursts lasted no more than a week. Now it is going off more frequently, and for longer maxima. Taichi Kato seems to be right in suggesting WX Hyi is trying to join "The ER UMa Club".
I presume you are writing about these hyperactive ER UMa dwarf novae
, so
why not post your Diskobolos article to vsnet-chat? I would like to
read it please....
cheers,
Fraser Farrell
Variable Stars Group
Astronomical Society of South Australia
WWW: http://www.gist.net.au/assa/ email: fraserf@dove.net.au
traditional: GPO Box 199, Adelaide, SA 5001, Australia
Taichi Kato wrote: > It's rather new to me since I have been taught TOADs are defined by > their amplitudes -- others like the outburst behavior or the SU UMa-nature > are frequently met characterstics of this group, and not a part of the > definition. Or is the term "TOAD" a synonym for the long-used "WZ Sge star"?
TOADs can be indeed connected to the WZ Sge class of stars. Although not appreciated by some people, the term TOAD was introduced also because WZ Sge is not a very good representative of its class. Only during one of its outbursts it showed a dip in the outburst light curve after a long main superoutburst and a subsequent rebrightening ala AL Com. The other two outbursts didn't show evidence for such dips in brightness.
> > The bright superoutburst and subsequent rebrightenings in V1028 Cyg > > occurred after a long quiescent period and may in this respect resemble > > TOADs. However, this star also show periods of regular normal and > > superoutburst behaviour. > > The outburst pattern of V1028 Cyg does not seem to be so regular. > Intervals between superoutbursts ranged between one and three years > -- quite similar to SW UMa as Kuulkers already pointed out.
I meant more regular normal and superoutburst behaviour with respect to the TOADs. TOADs such as Al Com and UZ Boo do not seem to show any normal outbursts. V1028 Cyg and SW UMa superoutburst more often than the latter and also show normal outbursts, not connected to the superoutbursts.
> I generally agree in this point. There seems to be a continuous transition > between "classcal" SU UMa stars and WZ Sge stars (or TOADs, if I understand > the definition correctly) in many points, but the existence of "early" or > "orbital" superhumps and the apparent lack of triggering normal outbursts > seem to be unique to the latter extreme end.
Indeed, the presence of "early" or "orbital" superhumps may be another criterium for being a TOAD.
Erik Kuulkers
On Fri, 7 Feb 1997, Fraser Farrell wrote: > Hypothesis to explain EG Cnc: it's being attacked by aliens ;) > However, there seems to be a similar star in the other direction > where my sky is dark - WX Hydri. > > Taichi Kato seems to be right in > suggesting WX Hyi is trying to join "The ER UMa Club".
I don't think WX Hyi is similar to EG Cnc. EG Cnc didn't show evidence for an outburst for about 2 decades, whereas WX Hyi has reltively frequent superoutbursts and normal outbursts. It could be that WX Hyi is evolving to a kind of ER UMa star, but I don't believe this is the case for EG Cnc. My guess is that EG Cnc will stay quiet now for a extended period of time, just like other TOADs or WZ Sge stars.
Erik Kuulkers
TOAD is not just another name for WZ Sge stars. These in fact. were fisrt defined by their dounle-peaked spectra (due to WZ Sge being at high i). TOADs have a number of defining properties. Thes eare outlined in the paper in ApJ paper in 1995 vol. 439. 337. Some are observational properties and some are guesses as to how the disk physics must work in order that current modeling sort of fits them.
observationally they are best described by large amplitudes, (6 or greater mags), long interoutburst intervals, short orbital periods (but not THE shortest, just below the gap), essentially no normal outbursts, outbursts are not apparently started by a normal outbusrt, light curves in optical show a "glitch" which is likely to be the accretion disk expansion "hitting" the tidal radius, sometimes (all? few?) the outbursts show predictable post-outburst brightenings, and they have superhumps, but only AFTER the glitch. The disks are possibly advected, and current disk models are NOW really correct to use in many cases as the m-dots in TOADs are lower them then general alpha-disk models.
there are additional properties as well, most are likely or predicted or based on theory.
Steve
Dr. Steve B. Howell Deptartment of Physics and Astronomy University of Wyoming P. O. Box 3905, University Station Laramie, WY 82071 USA Phone (307) 766-6150 Fax (307) 766-2652 e-mail: showell@kaya.uwyo.edu Homepage: http://wapiti.uwyo.edu/people/showell/ ITW Homepage: http://wapiti.uwyo.edu/toad/
In response to Steve Howell's comment in vsnet-chat 38:
> TOAD is not just another name for WZ Sge stars. These in fact. were fisrt > defined by their dounle-peaked spectra (due to WZ Sge being at high i). > TOADs have a number of defining properties.
I believe the "WZ Sge-type dwarf novae" were first proposed in Bailey 1979 (MNRAS 189, 41p). Bailey summarized in this article:
> The cataclysmic variables UZ Boo and WX Cet both resemble WZ Sge in > showing large outburst amplitudes (~8 mag). slow declines from outbursts, > and long intervals between outbursts. It is proposed that these three > stars form a distinct sub-group of the dwarf novae and that they may > all have similar binary structure.
How differs this description from the current TOAD definition? I have up to now understood there is only one point that TOADs have amplitudes larger than 6 magnitudes... There seems to be no mentioning about the double-lined emission spectrum as a part of his definition. Insightful was the inclusion in his list of UZ Boo!
Eric Kuulkers wrote (vsnet-chat 36):
> because WZ Sge is not a very good representative of its class. > Only during one of its outbursts it showed a dip in the outburst light curve > after a long main superoutburst and a subsequent rebrightening ala AL Com. > The other two outbursts didn't show evidence for such dips in brightness.
I can't fully understand this notion. Is WZ Sge a poor representative because it showed a dip and re-brightetning only one of its outbursts? I think this is only a matter of chance. Depending on the instabilities occurring after the main superoutbursts, stars may behave either as WZ Sge in 1913 and 1946 (no re-brighetnings), EG Cnc in 1996-1997 (repeated re-brightenings) or AL Com in 1995 and WZ Sge in 1978 (double superoutbursts). Dips or re-brightenings are common in WZ Sge stars, but should not be regarded as necessary conditions.
Fraser Farrell wrote:
> I would have liked to observe this one for myself, but looking through > the top of Adelaide's skyglow at 13th mag stars is a bit difficult for > me. However, there seems to be a similar star in the other direction > where my sky is dark - WX Hydri. > > The VSS RASNZ Circulars for October & November arrived this week. > Here's some more information about that odd superoutburst of WX Hyi: > > JD of maximum > 2450000+ duration (rise-peak-fall) days magnitude > ----------- ------------------------------ --------- > 363 2.9 - 5.0 - 5.7 (supermax) 12.0 > 380 1.1 - - 0.9 12.5 > 386 1.4 - 0.7 - 1.0 12.5 > 394 1.2 - 0.2 - 2.3 12.4 > 406 2.0 - - 1. 12.8 > 416 (Nov 28) 1.8 - 1. - 1.1 12.0 > How many of those maxima represent re-brightenings of a superoutburst? > Maybe all of them? WX Hyi certainly didn't "slow down" after the > superoutburst like many other UGSS's would have! In fact it may be even > more active than indicated; there has been a lot of cloudy weather in > the Southern Hemisphere lately. > > WX Hyi's frequency of outburst was about 2 or 3 times per month a few > years ago, and outbursts were typically less than 2 days long. Even its > superoutbursts lasted no more than a week. Now it is going off more > frequently, and for longer maxima. Taichi Kato seems to be right in > suggesting WX Hyi is trying to join "The ER UMa Club".
Greetings, Fraser,
I saw your note about WX Hydri. Rather than it being more active lately it seems to have reverted to the earlier behaviour patterns. We looked at this star from Auckland years ago - I think about the mid-1970s - looking for an orbital period using pep. At that time it seemed to be bright almost more often than it was faint and weekly outbursts weren't unusual.
Not too long ago (in the last couple of years) it was suggested that WX Hydri had stopped having outbursts. I'm unsure whether this was normal or super, or even when the supposed cessation occurred. Was this ever true?
In the normal outbursts we measured there was no pause at maximum - decline began immediately as with several other southern UGSU stars - although this may be difficult to pick visually. The supermaxima had good superhumps at the start but they soon became rather messy.
I meant to look at this star during the early summer but didn't manage it. Now it's just a little low - but maybe next year? I would have tried EG Cancri but 1997 seems to be a year for tropical storms hitting northern NZ!
Stan Walker
Go on to WX Hyi notes
Initial letter on WZ Sge 2001 by the VSNET Collaboration (Ishioka et al.)
Initial letter on WZ Sge 2001 by the VSNET Collaboration (Ishioka et al.)
(PDF)
HV Vir (1992) paper (PASJ) (PDF)
HV Vir (2002) paper (PASJ) (PDF)
SU UMa-type dwarf novae in general
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