[vsnet-alert 2025] USNO 0975.14594255: a possible variable star?

[Gianluca Masi <gianmasi@fr.flashnet.it>]

Dear Colleagues, 
I was having a look at the star field around V1315 Aql, using the USNO
A1.0. I noticed there is a star (I've been considering it as a
comparison one for doing photometry of the mentioned variable) with a
very remarkable B-R=4.9m color index. It is the USNO 0975.14594255. I
did few photometric measures of one of my recent images of that filed
(unfiltered frame), supposing it was taken in the R band (the chip used
in my ST-7, the Kodak KAF0400, is more sensitive in the red part of the
spectrum), then calculated mag differences between some of the stars in
the frame. Well, these differences are quite close (within 0.1mag) to
the ones obtained from the R mags for those stars as reported on the
USNO A1.0, except for the star in the subject, that is about 1 mag
brighter in my images than in the USNO A1.0. Here I report a summary of
my measures

C2-C3=1.12m (1.1)
C2-C= 0.74  (-0.3)
C2-D= 1.81  (1.7)
C3-D= 0.69  (0.8)
C-D = 1.07  (2.0)
C-C3= 0.38  (1.2)

The star in the subject is indicated by C, while the others are as in

http://vsnet.eurolink.it/comets/usn.jpg

The values between brackets are calculated from the USNO, the others
form my image.

I have also had a look at the Palomar Sky Survey
(http://archive.stsci.edu/cgi-bin/dss_form, first generation survey) and
there the star seems to be fainter than in my image, while the other
stars seems similar.

Do you think (considering your possible experience with similar cases)
this is due to a possible problem in digitizing the Palomar survey (but
stars around the one in the subject seems to have no problems), to the
different spectral response between the detectors or, also
considering the color index, maybe a possible Mira (red) variable? Do
you know
of any known variable in that position (RA=19h 13m 38.93s, D.:+12d 16'
23.2", J2000)?

Have a nice day/night.

Sincerely,
Gianluca


-- 
***********************************************************************
* Gianluca Masi                           "Two things fill the soul   *
* Via Madonna de Loco, 47               with awe and reverence [...]: *
* 03023 Ceccano (FR)                     the starry sky above me and  *
* ITALY                                    the moral law within me"   * 
* email: gianmasi@fr.flashnet.it                                      *
* http://vsnet.eurolink.it/comets/                        I. Kant       *
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