[vsolj-alert 168] SN1998di

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

SN1998di

　IAUC 6982に発見が公表された（発見者Schwartz）SN1998diは、実は銀河系内の
　極めて特異なタイプの激変星であることが判明しました。これらの天体（ヘリウ
　ム矮新星）は現在までにCR Boo, V803 Cen, CP Eriの３個しか発見されておらず、
　いずれも数十分の軌道周期、１−数日のアウトバースト周期、数十日に一度のス
　ーパーアウトバーストを起こすことが知られており、"SN1998di" も追跡が大変
　望まれます。16等とやや暗いですが（これが最大光度かどうかはわかりませんが）、
　北天の都合のよい位置にあり、超新星捜索の方もこの新変光星の光度を記録して
　おいていただますと大変貴重な資料になると思います。照合用の原画像等は以下
　に記載のURLをご覧ください。

　オリジナル情報は以下の通りです。

Date: Wed, 5 Aug 1998 09:28:38 +0900 (JST)
From: Taichi Kato <tkato>
To: vsnet-alert, vsnet-chat
Cc: pfactors@ix.netcom.com
Subject: [vsnet-alert 2001] (fwd) SN1998di (Schwartz)

Forwarded message on SN1998di, by permission of Michael Schwartz (originally
posted to isn_chat):

Date: Tue, 04 Aug 1998 15:05:25 -0700
From: "M. Schwartz" <pfactors@ix.netcom.com>
Subject: No SN1998di


Hi -

I knew that this would happen sooner or later, but SN1998di
is a cataclysmic variable (CV) that comes from a dwarf star
that has ignited due to material taken off an unseen companion.
The only consolation is that they are more rare than supernovae.

So, let's erase this one from the record books and let the
CVers take over.  Statistically speaking, this is never supposed
to happen.  So this means that the odds of it happening to you
are astronomical (so to speak).

Good hunting!!!

Mike

> S. Jha, P. Garnavich, P. Challis and R. Kirshner, Center for Astrophysics,
> report that a spectrum of SN 1998di taken by P. Berlind on Aug 4.4 UT at
> the Whipple Observatory 1.5-m telescope (+ FAST spectrograph) exhibits a
> blue continuum with shallow absorption troughs shortward of 500 nm. The
> object appears 4" east and 4" north of an anonymous galaxy with a
> recession velocity of 10750 +/- 30 km/s. The shallow absorption features
> have widths of approximately 3000 km/s (FWHM) and correspond to He I
> absorption at zero radial velocity. The spectrum resembles that of CR Boo,
> a hydrogen-deficient dwarf nova, near maximum (Patterson et al., 1997,
> PASP, 109, 1100).  We conclude that SN 1998di is a Galactic dwarf nova
> discovered in outburst projected near the distant anonymous galaxy. 
 
-- 
Michael Schwartz, Director
Tenagra Observatories, Ltd.
http://vsnet2.netcom.com/~pfactors/tenagra.html

Date: Wed, 5 Aug 1998 09:42:15 +0900 (JST)
From: Taichi Kato <tkato>
To: isn_chat@mbox.queen.it, vsnet-alert, vsnet-chat
Cc: pfactors@ix.netcom.com
Subject: [vsnet-alert 2002] Re: (fwd) SN1998di (Schwartz)

   There are only THREE helium dwarf novae.  CR Boo, V803 Cen and CP Eri.
Schwarz's discovery of "SN1998di" adds a great new specimen to this unique
subgroup of dwarf novae.  Observations are highly encouarged, are we are
happy to receive observations (e.g. to vsnet-obs or to myself, either from
the CV or SN communities) and feed back new fidings.  All of the known three
helium dwarf novae show very short-term variation (orbital period tens of
miniutes, outburst-like oscillations every sub-day to days, and superoutburst
quasi-periodically repeating with a typical time-scale of tens of days.
Continued observations by the same instrument, with which one may gain
aditional possibility of catching a supernova than by watching field CVs,
is highly encouraged.  The USNO A1.0-based (V-equivalent) VSNET chart
[vsnet-chart 66] is available at:

  http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-chart/msg00066.html

  (Original image by the discoverer:
   http://vsnet2.netcom.com/~pfactors/tenagra.html)

Regards,
Taichi Kato

From: "Tonny Vanmunster" <Tonny.Vanmunster@advalvas.be>
To: "cvc" <Tonny.Vanmunster@advalvas.be>
Date: Wed, 5 Aug 1998 00:28:12 +0200
Subject: [vsnet-alert 2000] CVC 167 (new cataclysmic variable in Draco)

BELGIAN ASTRONOMICAL SOCIETY V.V.S. -  Working Group Variable Stars
Cataclysmic Variables Circular No.167               1998, August 04
Ed.: T. Vanmunster, Walhostraat 1A, 3401 Landen, BELGIUM
     Internet: Tonny.Vanmunster@advalvas.be       TEL. 32-11-831504
     CVC Web Page : http://vsnet.cba.phys.columbia.edu/cvc
===================================================================

New cataclysmic variable in Draco
=================================

We have been informed by Michael Schwartz, Cottage Grove, OR about
his discovery of a new cataclysmic variable in Draco : "I am 
'responsible' for finding supernova 1998di in an anonymous galaxy
(see IAUC 6982, that was issued on August 3rd). However, spectral 
observations now reveal that this is not a supernova, but a galactic
dwarf nova in outburst, projected near a distant anonymous galaxy".

Michael Schwartz kindly has sent us full details about the related
spectrographic analysis by Jha, Garnavich, Challis and Kirshner 
(Center for Astrophysics), that likely will appear in an IAUC 
tomorrow. The spectrum of the new dwarf nova resembles that of the
helium dwarf nova CR Boo near maximum (Patterson et al., 1997, PASP, 
109, 1100).  

The new object is located at RA = 19h24m38s.19, Decl = +59o41'46".7 
(equinox 2000.0), which is about 0".6 east and 3".8 north of the 
nucleus of an anonymous galaxy. A picture of the new object is 
available at the following URL : 
http://vsnet2.netcom.com/~pfactors/tenagra.html

Some photometric observations :

1998 Jul 22.46 UT, [19    (M. Schwartz, unfiltered CCD image);
     Aug 02.48 UT,  16.8  (M. Schwartz, unfiltered CCD image);


We strongly recommend CCD observers to photometrically monitor this
object.


Tonny Vanmunster

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp