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TCP J18010186-2951258: possible nova (10.8 mag) in Sagittarius

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SPK
SPK's picture
TCP J18010186-2951258: possible nova (10.8 mag) in Sagittarius

TCP J18010186-2951258 (N:)

Discovery details:
R.A. 18h01m01.86s, Decl. -29°51'25.8" (J2000.0)
2018 July 13.4938 UT, 10.8 mag (unfiltered)
Discoverer: Tadashi Kojima (Gunma-ken, Japan)

2018 07 13.494 UT
Discovered by T. Kojima, Gunma-ken, Japan, who found this on six frames (limiting mag. = 13.3) taken by Canon EOS 6D + 200-mm f/3.2 lens. Nothing is visible at this location on a frame taken on 2018 July 2.522. There is a star (mag.= 15.0) at 01s.98 and 23".7 on USNO-A2.

2018 07 13.63 UT
Crowded field. The current brightening was first detected by the ASAS-SN Sky Patrol (Shappee et al. 2014ApJ...788...48S and Kochanek et al. 2017PASP..129j4502K) on 2018 July 4.169 UT at Vmag. 13.9; the latest available observation is July 12.148 UT, Vmag. 12.0. Light curve at
https://asas-sn.osu.edu/light_curves/2cffca21-6b86-4488-be2a-b473ab1d0256
--- Patrick Schmeer (Saarbrücken-Bischmisheim, Germany)

http://www.cbat.eps.harvard.edu/unconf/followups/J18010186-2951258.html

Spectroscopy, precise astrometry, and multiband photometry are urgently required.

Clear skies,
Patrick

AAX
AAX's picture
Hi friends,

Hi friends,

I observed this object, visually: follows my report.

2018-07-13 at 21:42 UT, magnitude 11.4 (comps. 106, 114; AAVSO chart X23045FAE)

with regards,

AAX

Deconinck Michel
Deconinck Michel's picture
Hi, I just observed this

Hi, I just observed this object too but my visual magnitude estimation 20:52 UTC was very close to 10.6 from the chart X23075EVK and 10.7 at 21:04 with a Tycho2 catalogue. ???

Michel

Christian Buil
Christian Buil's picture
Spectrographic observation

Observation of transient TCP J18010186-2951258

From Christian Buil and Olivier Garde a spectrum of  TCP J18010186-2951258 taken the 2018 07 13.841  from Observatoire de Haute-Provence observatory UAI code 511 (annual spectrographic workhop). The object seem not a nova. Halpha is noted very narrow - spectra in following link:

http://www.astrosurf.com/buil/forum15/outburst_sgr.png

We believe it is a CV.

For your information:
Christian Buil spectrum taken with a RC 0.25m telescope with LISA spectrograph, spectral resolution R=850. Exposure time 8x300s=2400sec. Taken from Observatoire de Haute-Provence observatory UAI code 511.

Christian Buil

Olivier GARDE
Spectrographic observation

Observation of transient TCP J18010186-2951258

From Christian Buil and Olivier Garde a spectrum of  TCP J18010186-2951258 taken the 2018 07 13.866 from Observatoire de Haute Provence Observatory UAI code 511 during annual spectrographic workshop). The object seem not a nova. Halpha is noted very narrow 

We believe it's a CV.

Olivier Garde spectrum taken with a C14 (0.355m @ f/d7 telescope) with LISA spectrograph R=700, exposure time : 10x600s=6000s (from Observatoire de Haute Provence in France UAI code 511)

Deconinck Michel
Deconinck Michel's picture
Thank you Patrick for this

Thank you Patrick for this new alert.  Thank you too for the spectral image Olivier and Christian.  Do you have an idea, what type of star can gives such a spectral signature?

Christian and Olivier, you know that you'r just one hour from my home by car.

Here join the sketch of the field I did yesterday.

SPK
SPK's picture
TCP J18010186-2951258 is a microlensing event (ATel #11853)

Subo Dong (KIAA-PKU), K. Z. Stanek, C. S. Kochanek, T. Jayasinghe, T. A. Thompson (OSU), J. L. Prieto (Diego Portales; MAS), B. J. Shappee (Univ. of Hawaii), T. W.-S. Holoien (Carnegie):
"ASAS-SN Confirmation of a Bright and Possible High-Magnification Microlensing Event" (ATel #11853)
http://www.astronomerstelegram.org/?read=11853

Deconinck Michel
Deconinck Michel's picture
Here my tonight (2018/07/15

Here my tonight (2018/07/15 22:15 UTC) visual estimations : +11.8 / +11.9

Deconinck Michel
Deconinck Michel's picture
Contradictory reports

Here join two contradictory reports about this object.

The first one suggest a binary lens

http://www.astronomerstelegram.org/?read=11882

With thank you to the AAVSO observers

and this one a variable star

http://www.astronomerstelegram.org/?read=11883

Michel

Sebastian Otero
Sebastian Otero's picture
Not a contradiction

Hi Michel,
The star is a known variable discovered by OGLE years ago. What the second report says is that this is likely not a binary lens not that the event is not caused by a microlens. Single lens versus binary lens. Actually the confusion may arise from the fact that the known variations are amplified during the lensing event, so a secondary peak is not caused by the existence of a second object but by the intrinsic variability of the star.

Cheers,
Sebastian

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