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TCP J19083989+1210033: new transient (11.4 mag) in Aquila

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SPK
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TCP J19083989+1210033: new transient (11.4 mag) in Aquila

TCP J19083989+1210033

RA 19h08m39.89s, DEC +12°10'03.3" (J2000.0)
2018 April 4.7561 UT, 11.4 mag (CCD, unfiltered)
Discoverer: Tadashi Kojima (Gunma-ken, Japan)

2018 04 04.756 UT
Discovered by T. Kojima, Gunma-ken, Japan, on six frames with five second exposure using Canon EOS 6D digital camera + 200-mm f/3.2 lens under the limiting mag = 12.5, who writes nothing is visible at this location on the previous frames (limit mag = 13.5) taken 2018 Mar. 22.786, 27.771 and Apr. 2.760 UT.

2018 04 05.25 UT
A reddish Gaia DR1 source at RA 19h08m39.947s, DEC +12°10'03.34" (J2000.0; G= 13.75 mag) is 1" away; APASS magnitudes V= 15.11, B-V= +1.61; GSC2.3 magnitudes Bj= 15.88, V= 14.78, F= 13.51, N= 12.01; light curve for this star (NSVS 11148572) at
https://skydot.lanl.gov/nsvs/star.php?num=11148572
Latest available ASAS-SN Sky Patrol observation (Shappee et al. 2014ApJ...788...48S and Kochanek et al. 2017PASP..129j4502K): 2018 April 1.567 UT, V= 15.0 mag:
https://asas-sn.osu.edu/light_curves/111ff0b2-dc29-4d5b-b17f-e368c39552c7
The ROSAT (X-ray) source 2RXS J190835.6+120923 is 1' away.
--- Patrick Schmeer (Saarbrücken-Bischmisheim, Germany)

Follow-up reports: http://www.cbat.eps.harvard.edu/unconf/followups/J19083989+1210033.html

Spectroscopy and precise astrometry are urgently required.

Clear skies,
Patrick

HBB
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Transient in Aquila

I just took some images of that area and see nothing as bright as 11.4 mag.  The brightest object closest to those coordinates is at 19 08 39.96, +12 10 3.5 that I measure at 15.295 V.

SPK
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Flare star?

This may be a flare star, if the reported brightening on 2018 April 4.7561 UT was real.

SPK
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Previous flares?

Róbert Fidrich and I noticed several brightenings in the ASAS-3 (and one brightening in the ASAS-SN Sky Patrol) light curve: maybe flares, maybe outliers.
http://www.astrouw.edu.pl/cgi-asas/asas_variable/190839+1210.1,asas3,0,0...

SPK
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Likely flare star (M4 V)

Professor Roberto Nesci (INAF-IAPS) writes (vsnet-alert 22053):
"From the 2MASS magnitudes (J=10.884 H=10.293 K=10.010) the star is an M4 V, so likely a flare star."
http://ooruri.kusastro.kyoto-u.ac.jp/mailarchive/vsnet-alert/22053

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