[vsnet-alert 8648] (fwd) New dwarf nova near M27,
chart information (Renz)
Taichi Kato
tkato at kusastro.kyoto-u.ac.jp
Mon Aug 29 09:04:30 JST 2005
Information from W. Renz:
Subject: Charts and Sequence for New Object near M27 (VAR Vul 05)
Date: Sun, 28 Aug 2005 22:53:15 +0200
Hello
First a summary what is known about the variable up to now:
Tonny Vanmuster and Brian Martin detected humps of 0.3 mag
with an period of about 82 min that are typical for dwarf novae
(UG Gem stars) of type SU UMa (UGSU stars). If it shows a
steep drop in the mag values within the next days, its an clue
that its a 'normal' UGSU star. These have super outburst cycles
of about 100 to 1000 days and normal outburst that are shorter
and about 1 mag fainter than super outbursts.
But the amplitude of about 10 mag is pretty large for a 'normal'
UGSU star. So it would be a TOAD (tremendous outburst
amplitude dwarf nova). As the outburst amplitude of dwarf novae
get larger with longer outburst cycles, it might be one of the rare
UGSU star of subtype WZ Sge (UGSU/WZ). These have super
outburst cycles of more than 1000 and up to a few 10000 days
and show no normal outbursts like the other UGSU stars.=20
As some recurrent novae behave similar to UGSU/WZ stars
(actually most UGSU/WZ stars were first classified as recurrent
novae before their true nature was discovered), there is still a
possibility that its one of these. The outburst amplitude of about
10 mag alone would still allow an interpretation as a slower nova.
In the end just further observations and a spectrum can prove if
its a dwarf nova (with a bright blue continuum due to a heated
disk that transforms potential energy into radiation) or a
classical/recurrent nova (with a nuclear run-away that blows the
outer part of the collected hydrogen hull into space).
What can we amateurs do (execpt of waiting for the
professionals to make a spectrum) ?
- Monitor the variable with our CCDs for the next three month
(UGSU/WZ stars show rebrightenings, so it might not be all
over after you made your first negative CCD observation)
- Check our recently made images of M27 to isolate the date/
time of the current outburst (should have been between Aug
11 and Aug 14) and an accurate maximum brightness.
- Check our older film and CCD images for previous outbursts
(if its a UGSU star or a recurrent nova it must have shown
earlier outburst). If you own older books or magazines with
images of M27, check them too. If you have access to a plate
archive like Harvard or Sonneberg and some time to spend,
you might check their plates too.
I've created the VarVul05 Yahoo group at
http://groups.yahoo.com/group/VarVul05/
to collecting data from 'pretty pictures'.
Any data of VAR Vul 05 that goes down to 15 mag and deeper
is of interest and will be forwarded to the AAVSO, cvnet and
vsnet.
Due to its vicinage to M27, this is the unique chance to collect
data of several decades for this new variable.
Please take part in this exciting scientific campaign.
Thanks for your efford in advance.
For every image I need the following data:
- Date & mid-time in UT, if the the image was made in a single
night.
Date range in UT, if images were made over several nights.
Please, give the time if it is still (easily) available. The time is
required if its near and in outburst. Use the data of the lumi-
nance image(s) if you used a luminance channel.
- mag: Magnitude of VAR Vul 05 if detected.
- LM: Approximate limiting magnitude of image.
- T: Type of the photometric band of the magnitudes used for
mag and LM (B, V, Rc or Ic)
- Image: Used filter channel(s)
(e.g. C, L, R, G, B, Ha, OIII, SII, HaOIII, LRGB, CRGB, RGB, ...)=20
- Observer data: First name, last name, city, country
- If possible the used image itself or a link to the image.
You can access the official (15'x15') AAVSO chart of VAR Vul 05
(942 KB) at:
http://www.aavso.org/charts/VUL/VAR_VUL_05/
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
I've placed two charts and the below sequence of the close
surrounding (2'x2') of VAR Vul 05 in the files section of the
VarVul05 Yahoo group:
http://groups.yahoo.com/group/VarVul05/files/
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
Using the this sequence everyone can easily detect the limiting
magnitude of an image down to 20 mag:
ID RA (J2000) DEC n q B (B-V) V (V-R)c Rc =
(R-I)c Ic (V-I)c
A 299.975600 22.697012 7 + 15.298 0.837 14.461 0.508 13.953 =
0.516 13.437 1.024
B 299.945650 22.723832 8 + 16.114 0.907 15.207 0.530 14.677 =
0.542 14.135 1.072
C 299.976820 22.717449 7 + 17.076 1.037 16.039 0.649 15.390 =
0.647 14.743 1.296
D 299.976498 22.708397 7 + 17.040 0.942 16.098 0.548 15.550 =
0.514 15.036 1.062
E 299.953540 22.700717 7 + 18.282 1.645 16.637 0.960 15.677 =
0.910 14.767 1.870
F 299.952621 22.711413 10 17.918 1.234 16.684 0.762 15.922 =
0.741 15.181 1.503
G 299.973373 22.719585 8 + 18.544 1.278 17.266 0.803 16.463 =
0.759 15.704 1.562
H 299.966295 22.711495 8 18.998 1.342 17.656 0.844 16.812 =
0.799 16.013 1.643
I 299.964065 22.715243 7 + 19.537 1.673 17.864 1.014 16.850 =
0.963 15.887 1.977
J 299.970520 22.706022 8 19.196 1.300 17.896 0.762 17.134 =
0.728 16.406 1.490
K 299.962465 22.714542 11 19.508 1.504 18.004 0.749 17.255 =
0.844 16.411 1.593
L 299.960314 22.711854 11 - 19.573 1.366 18.207 0.349 17.858 =
0.656 17.202 1.005
M 299.968522 22.715432 7 + 20.108 1.572 18.536 0.895 17.641 =
0.909 16.732 1.804
N 299.965691 22.715633 9 20.356 1.626 18.730 1.110 17.620 =
0.936 16.684 2.046
O 299.962649 22.709794 9 20.074 1.329 18.745 0.356 18.389 =
0.779 17.610 1.135
P 299.980689 22.698751 8 (+) 19.119 0.046 19.073 -0.013 19.086 =
0.254 18.832 0.241
Q 299.967575 22.704426 8 + 20.513 1.322 19.191 1.092 18.099 =
0.824 17.275 1.916
R 299.963127 22.708488 9 - 20.624 1.246 19.378 0.181 19.197 =
0.962 18.235 1.143
S 299.965496 22.704913 7 (+) 21.407 2.020 19.387 1.147 18.240 =
1.243 16.997 2.390
T 299.969273 22.709816 5 - 21.046 1.552 19.494 0.513 18.981 =
0.830 18.151 1.343
Notes:
1. There is an AAVSO f scale chart dated 050823 (15'x15') for
this variable. The only star in common is star D labeled 161 in
the AAVSO chart.
2. Stars with smaller than average errors for their bightness are
labeled '+' in column q. Stars with larger errors are labeled '-'
(due to near companions or possible variability). The average
V errors are < 0.03 mag at the bright end and <=3D 0.06 mag at
the faint end. The bluest star P has small errors just in B, V and
(B-V). The reddest star S has a larger error just in (B-V) and B.
3. Stars with good photometry were taken from m27good.dat.
The other, mostly fainter stars were taken from m27.dat.
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/
4. The main aim of this sequence is not to give the best possible
comp stars, but to determine the limiting magnitude near the
variable. If you use this sequence for photometry, use the bluer
+ stars for the zero point (the varaible has a (V-Ic) of about 0.3
mag).
5. The field is very reddened due to interstellar gallactic
extinction. The comp stars B, E and F lie within the first shell of
M27. The comp stars A, C, D, G and P lie within the third shell.
All others lie within or at the outer boarder of the second shell.
There is just one star with good photometry in m27good.dat=20
and 8 stars with acceptable photometry in m27.dat with a (B-V)
< 0.5 mag. But none of them is in the range 14.2-18.2 magV or
close to the variable.
- For blue sensitive film, B and Hbeta filtered images
use the B mags.
- For green sensitive film, G, V and OIII filtered images
use the V mags.
- For red sensitive film, R, Rc, Ha and SII filtered images
use the Rc mags.
- For Ic and NIR filtered images
use the Ic mags.
- For unfiltered, clear and luminance filtered images it depends
on the used CCD chip.
- If it has its max QE below 540 nm (e.g. Kodak KAI and Sony
interline CCD chips)
use the V mags.
- It it has its max QE above 640 nm (e.g. most Kodak KAF non-
E and TI full frame CCD chips)
use the Rc mags.
- The Kodak KAF blue-enhanced E chip images might be
reduced using the V or Rc mags as the QE lies in between.
- For LRGB and CRGB images see clear and luminance filtered
images above.
- For RGB images it depends on the composition. If the G image
is deep enough, then use it with V mags.
If you are not sure what mags to use, take a look at the stars D
and E. If D appears obviously brighter than E, then use V mags.
If they appear about of equal brightness, then use Rc mags.
You can also take a look at stars P and Q. If they appear about
of equal brightness, then use V mags. If Q appears considerable
brighter than P, then use Rc mags.=20
Please feel free to forward this email and the charts to others that
might be interested.
Clear skies
Wolfgang
--=20
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV =3D WRe.vsnet =3D RWG.AAVSO
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