[vsnet-alert 14084] Re: possible real-time flare detection of a new flare star

[Seiichi Yoshida]

Dear colleagues,

* Note that this reports the follow-up information and summary of our 
  possible real-time flare detection in December, posted on Dec. 23
  [vsnet-alert 13989].

  http://www.aerith.net/misao/variable/MisV1445.html

On December 17, 2011, we discovered a rapid-brightening star from the
survey images taken by Youichirou Nakashima in the course of the MISAO
Project. It is possible real-time flare detection of a new flare star.

The possible flare occured on a star in Taurus, USNO-A2.0 1125.02693028.
It is normally fainter than 16 mag, but brightened up to 14.7 mag in
outburst on Dec. 17.

It is not a known variable star. So it will be a new flare star. We
the MISAO Project assigned a new variable star designation MisV1445 to
this star.

This flare star was discovered by Seiichi Yoshida (MISAO Project) in
the MISAO Project nova survey. It was picked up as one of the nova
candidates from Youichirou Nakashima (Okayama, Japan)'s unfiltered CCD
images on 2011 Dec. 17 by the PIXY System 2. The astrometry from
Nakashima's images is: R.A. 05h41m30s.52, Decl. +22o39'27".4 (equinox
J2000.0).

MisV1445 was in the frame of 4 images on Dec. 17. The star is not
visible on the first image, visible but faint on the second image, and
bright on the third and fourth images. It brightened rapidly by 2 mag
or more withiin only 4 minutes.

    Date and Time (UT)        Magnitude
    -------------------------------------------
    Dec. 17.76277 (18:18:23)  fainter than 16.8
    Dec. 17.76411 (18:20:19)  15.8
    Dec. 17.76545 (18:22:15)  14.7
    Dec. 17.76678 (18:24:10)  14.8

MisV1445 was not detected on our past images, 5 nights between January
and November in 2011 by Nakashima, or 2000 February by Nobuo Ohkura
(Okayama, Japan). It was fainter than 16.5-17.4 mag.

    Date          Observer   Magnitude
    ------------------------------------------
    2011 Nov. 23  Nakashima  fainter than 16.9
    2011 Feb. 22  Nakashima  fainter than 16.8
    2011 Feb.  3  Nakashima  fainter than 16.8
    2011 Jan. 26  Nakashima  fainter than 17.3
    2011 Jan. 10  Nakashima  fainter than 17.4
    2000 Feb. 26  Ohkura     fainter than 16.5

    Instruments:
    Youichirou Nakashima -- Canon 500-mm f/4.5 camera lens + SBIG ST-8
    Nobuo Ohkura -- 0.16-m f/3.8 Wright-Schmidt reflector + SBIG ST-8(ABG)

Yoshida noticed this flare event soon after midnight on Dec. 23
(JST). Nakashima and Masayuki Suzuki observed it soon for
confirmation. But MisV1445 has already faded, and we could not confirm
the flare event.

    Date          Observer   Magnitude
    ------------------------------------------
    2011 Dec. 22  Nakashima  fainter than 17.0
    2011 Dec. 24  Suzuki     18.0

    Instruments:
    Youichirou Nakashima -- Canon 500-mm f/4.5 camera lens + SBIG ST-8
    Masayuki Suzuki -- GRAS-017 0.43-m f/6.8 + FLI ProLine E2V
                       CCD47-10-1-109 Deep Depletion Fused Silica (Near-IR)

The original image files of the flare event on Dec. 17 can be
downloaded at the web page (SBIG format). MisV1445 is visible at
different (x,y) position on three images. So the brightening seems to
be a real event.

Here is the data of MisV1445 recorded in the USNO-A2.0 catalog.

  USNO-A2.0 1125.02693028
    R.A.    05h41m30s.523
    Decl.   +22o39'26".96
    Mag(R)  17.9
    Mag(B)  19.7

Masayuki Suzuki researched the USNO-B1.0 catalog. Here is the data of
MisV1445 recorded in the USNO-B1.0 catalog.

  USNO-B1.0 1126-0102137
    R.A.     05h41m30s.51
    Decl.    +22o39'26".8
    Mag(B1)  20.31
    Mag(R1)  17.26
    Mag(B2)  19.81
    Mag(R2)  18.15
    Mag(I)   15.77

A large flare tends to be observed on a nearby red dwarf. The color
recorded in those star catalogs coincides to that. However, the proper
motion of MisV1445 is 0 milliarcsec/year in the USNO-B1.0 catalog. It
may suggest that MisV1445 is not a nearby star.

Best regards,

--
Seiichi Yoshida
comet at aerith.net
http://www.aerith.net/