[vsnet-alert 8670] (fwd) VarVul05 very faint (possible dip in WZ Sge-type outburst?) (forwarded from Renz)

[Taichi Kato]

Subject: Re: VarVul05 very faint: mag > 18.5 on Sep 06 UT (New object near M27)
Date: Tue, 6 Sep 2005 06:44:50 +0200

Hello Michael

Thanks for the info.
Please, report your measurement even if it has a larger error/
uncertainty than usual and continue to monitor it.

The last measurements reported to the AAVSO are:
>    SEP 01.2611  2453614.7611   17.58  GBL   CCDB  =20
>    SEP 01.2646  2453614.7646   17.02  GBL   CCDV  =20
>    SEP 01.2549  2453614.7549   16.87  GBL   CCDR  =20
>    SEP 01.2451  2453614.7451   16.5   RR    BCCDI =20
and to the vsnet:
>    20050901.839  170V  (J. Nicolas)
>    20050901.869  169R  (J. Nicolas)
>    20050901.899  166I  (J. Nicolas)
and by private communication with J=F6rg Hanisch:
>    2005-09-03,945 17,40 +-0,06mag (CV)  ; comm: 4 Ref Stars

VAR Vul 05 showed before SEP 01 a fading trend of about just
0.1 mag/day. If its now as bright as comp star O it must have
undergone a much more rapid fading within the last 2 days.
So it should have now a color corrected brightness of about 18.9
magV / 18.3 magR. Thats about 1.9 magV / 1.4 magR below the
last BVRI measurements. That looks like as Michael caught VAR
Vul 05 at the rapid fading (about 1.2 mag/day) to the transient
dip (or already at its buttom) thats typical for UGSU/WZ stars.=20

For an examples of the behaviour of UGSU/WZ stars see:
http://www.kusastro.kyoto-u.ac.jp/vsnet/DNe/wzsge01.html

If its a UGSU/WZ star, it should start to show rebrightenings back
to about 17 mag within the next few days. So everybody, please,
intensify your CCD observations of VAR Vul 05 (or M27) that are
strongly encouraged.
Who of you will be the first to detect a rebrightening and prove
the UGSU/WZ nature of VAR Vul 05 ?

Even negative measurements at 17.3 mag or fainter are valuable
to determine the dips between the rebrightenings. But take care
of the close 18.7magV/18.4magR and 19.4magV/19.2magR
neighbors if you image with a shorter focal length. And apply a
color correction if possible as the comp stars are much redder
than the variable.
(see the (15'x15') AAVSO chart of VAR Vul 05 (942 KB) at:
http://www.aavso.org/charts/VUL/VAR_VUL_05/
http://www.aavso.org/charts/VUL/VAR_VUL_05/VARVUL05-F.PNG
or a down sized version (175 KB) at:
http://groups.yahoo.com/group/VarVul05/files/
http://groups.yahoo.com/group/VarVul05/files/AAVSOchart_VARVUL05-F.jpg
and my 2'x2' limiting mag sequence and BVRcIc charts at
http://groups.yahoo.com/group/VarVul05/files/varvul05lm.seq
http://groups.yahoo.com/group/VarVul05/files/VarVul05lm-color.jpg
http://groups.yahoo.com/group/VarVul05/files/VarVul05lm-print.jpg
in the files section of the VarVul05 Yahoo group:
http://groups.yahoo.com/group/VarVul05/
For color correction see Arne Hendens 'THE M67 UNFILTERED
PHOTOMETRY EXPERIMENT' at:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/m67/
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=3D2000JAVSO..29..=
.35H
http://www.aavso.org/publications/ejaavso/v29n1/35.shtml )

Good luck in hunting.

Clear skies
  Wolfgang

--=20
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV =3D WRe.vsnet =3D RWG.AAVSO



----- Original Message -----=20
From: "Stupendous_Mn" mwrsps at ri...
To: <VarVul05 at yahoogroups.com>
Sent: Tuesday, September 06, 2005 3:35 AM
Subject: [VarVul05] VarVul05 very faint: mag > 18.5 on Sep 06 UT

> I tried measuring the variable from the RIT Observatory on UT Sep 06
> 01:00, using a 12-inch telescope and SBIG ST-8E CCD camera without
> filter, exposures of 120 seconds.  No luck.  Very rough reductions at
> the telescope show that the variable star is very faint: it is only
> barely detected in my images, at roughly the same level as the nearby
> star "O" on the color chart posted in the VarVul Yahoogroups file
> section.
>     http://groups.yahoo.com/group/VarVul05/files/
>=20
> I would guess that it must be fainter than V=3D18, perhaps as faint as
> V=3D19.  Too faint for me :-(
>=20
>                                      Michael Richmond
>
>=20
> <*> To visit your group on the web, go to:
>     http://groups.yahoo.com/group/VarVul05/