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Dear colleagues,
Taichi Kato wrote:
> We have received a notification from GCVS Dr. Samus, that the proposed
> identification of TmzV868 looks incompatible with the proposed
> classification. It would be likely that the object may not be a Mira-type
> object as originally supposed.
Here I introduce the photometry by the MISAO Project.
Please see also at:
Photometry of TmzV868
http://vsnet.aerith.net/misao/report/variable/TmzV868.html
In the course of MISAO Project, Nobuo Ohkura took 21 unfiltered CCD
images of this field on 6 nights between 2000 August and 2001
November, using the 0.16-m f/3.8 Wright-Schmidt reflector and the
500-mm camera lens.
Date Instruments N. of images
-------------------------------------------
2000 Aug. 28 reflector 3 images
2000 Dec. 24 camera lens 4 images
2001 Sept.23 reflector 3 images
2001 Oct. 10 camera lens 4 images
2001 Nov. 15 reflector 3 images
2001 Nov. 24 camera lens 4 images
Here is the image of TmzV868.
http://vsnet.aerith.net/misao/report/variable/TmzV868/chart.gif
Here reports the photometry of TmzV868 and IRAS 01446+5602, using the
five reference stars (A - E).
The information of TmzV868, IRAS 01446+5602, and the five reference
stars are as follows.
Reference stars:
A: USNO-A2.0 1425.02447635 01h47m55s.633 +56o17'28".97 Mag(R):12.5 Mag(B):13.8
B: USNO-A2.0 1425.02450404 01h48m01s.846 +56o15'13".50 Mag(R):12.9 Mag(B):13.8
C: USNO-A2.0 1425.02456261 01h48m15s.226 +56o16'32".29 Mag(R):13.7 Mag(B):15.0
D: USNO-A2.0 1425.02451390 01h48m04s.023 +56o14'44".49 Mag(R):14.1 Mag(B):15.7
E: USNO-A2.0 1425.02455845 01h48m14s.325 +56o16'07".38 Mag(R):14.4 Mag(B):15.3
Target Stars:
1: TmzV868 01h47m57s.60 +56o17'36".9 Mag(max):13.5 Mag(min):<14.5 MagSystem:p Type:M:
= USNO-A2.0 1425.02448485 01h47m57s.576 +56o17'37".14 Mag(R):14.4 Mag(B):15.3
2: IRAS 01446+5602 01h47m57s.7 +56o17'51" Ellipse:20x3" P.A.:56 Flux(12):1.114 Flux(25):0.6362 Flux(60):<0.4000 Flux(100):<5.918 Var:45%
= USNO-A2.0 1425.02448803 01h47m58s.297 +56o17'54".42 Mag(R):12.3 Mag(B):15.2
Seiichi Yoshida operated PSF photometry. The point spread function is
created for each image using the five reference stars.
The table below shows the photometry of TmzV868, IRAS 01446+5602, and
the five reference stars. The magnitude is a relative value to the
brightness of the point spread function, the compounded brightness of
the five reference stars.
IRAS
Star Star Star Star Star 01446 TmzV
JD A B C D E +5602 868
--------------------------------------------------------------
2451785.21826, 1.39, 1.16, 2.08, 2.25, 2.45, -0.99, 2.89
2451785.22012, 1.45, 1.11, 2.02, 2.31, 2.46, -0.95, 2.79
2451785.22197, 1.47, 1.13, 1.95, 2.36, 2.40, -0.90, 2.86
2451902.93351, 1.37, 1.19, 1.92, 2.33, 2.55, -1.30, 2.58
2451902.93536, 1.42, 1.18, 1.99, 2.25, 2.42, -1.32, 2.47
2451902.93722, 1.41, 1.14, 2.00, 2.32, 2.47, -1.32, 2.65
2451902.93907, 1.39, 1.20, 2.00, 2.30, 2.39, -1.24, 2.71
2452176.15456, 1.43, 1.20, 1.91, 2.27, 2.44, -1.15, 2.70
2452176.15642, 1.46, 1.15, 1.99, 2.28, 2.40, -1.13, 2.81
2452176.15828, 1.46, 1.19, 1.91, 2.36, 2.32, -1.12, 2.80
2452193.14162, 1.40, 1.17, 1.93, 2.35, 2.49, -1.17, 2.63
2452193.14359, 1.35, 1.18, 1.93, 2.45, 2.50, -1.10, 2.71
2452193.14556, 1.41, 1.17, 1.93, 2.30, 2.51, -1.03, 2.52
2452193.14752, 1.47, 1.14, 2.02, 2.26, 2.39, -1.05, 2.55
2452229.06743, 1.50, 1.08, 2.01, 2.35, 2.43, -1.07, 2.81
2452229.06940, 1.38, 1.17, 2.05, 2.28, 2.46, -1.14, 2.75
2452229.07138, 1.44, 1.19, 1.91, 2.36, 2.37, -1.03, 2.84
2452238.01793, 1.43, 1.12, 2.00, 2.31, 2.51, -1.10, 2.66
2452238.01990, 1.38, 1.16, 2.03, 2.31, 2.47, -1.05, 2.58
2452238.02188, 1.41, 1.22, 1.99, 2.20, 2.42, -0.99, 2.58
2452238.02384, 1.45, 1.14, 2.02, 2.30, 2.39, -0.96, 2.66
Here is the light curve.
http://vsnet.aerith.net/misao/report/variable/TmzV868/curve-JD.gif
The brightness of the five reference stars look constant.
The light curve of IRAS 01446+5602 looks variable. The variability of
this object is also suggested by the IRAS record as 45%. So it may be
a new red variable star, with a range of at least 0.3 mag.
But TmzV868 was remarked as "TmzV868 is located between GSC3692.2365
star (N) and GSC3692.946 star (SW)" in the orginal announcement
[vsnet-newvar 1188]. So it does not mean the mis-identification of
TmzV868.
The brightness of TmzV868 shows a possible systematic difference
between the reflector and the camera lens. The graph below shows the
measured magnitude for each image.
http://vsnet.aerith.net/misao/report/variable/TmzV868/curve-image.gif
TmzV868 seems faint on all reflector images, and bright on all camera
lens images.
The magnitude of TmzV868 on each night is as follows:
Instruments Date Magnitude
---------------------------------------------
reflector 2000 Aug. 28 2.85 +/- 0.042
2001 Sept.23 2.76 +/- 0.050
2001 Nov. 15 2.80 +/- 0.037
---------------------------------------------
camera lens 2000 Dec. 24 2.60 +/- 0.089
2001 Oct. 10 2.60 +/- 0.074
2001 Nov. 24 2.62 +/- 0.040
---------------------------------------------
which suggests the systematic difference of 0.20 mag.
A systematic difference of magnitude between the reflector and camera
lens is sometimes found in the case of a very red star. But the
USNO-A2.0 color of TmzV868 is not red, B-R = 0.9 mag. So the reason is
still uncertain.
Anyway, the brightness of TmzV868 is almost constant among the
reflector images, or among the camera lens images. It supports that
TmzV868 is not a Mira-type object as originally supposed.
Conclusion:
No evident variation of TmzV868 was detected, which supports that
TmzV868 is not a Mira-type object as originally supposed.
Nearby IRAS 01446+5602 may be a red variable, but it does not mean the
mis-identification of TmzV868.
TmzV868 shows a possible systematic difference of magnitude between
the reflector and camera lens, but the reason is uncertain.
Best regards,
--
Seiichi Yoshida
comet@aerith.net
http://vsnet.aerith.net/
Return to the Powerful Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
