Dear Sebastián,

Sorry for the late response. It seems the list didn't forward your e-mail for some reason (and I thank Keisuke for forwarding it to me).

I apologize we confused you. "Identical" was my mistake and overstatement. Thank you very much for pointing it out.

We pointed the telescope to the position of Gaia EDR3 4104372315454847232 (18:30:23.466, -13:55:42.17). I confirmed the object was almost at the center of the IFU (FoV 8.4'' x 8.0''), and therefore the star should prefer

1. 18 30 23.47 -13 55 42.0  (2.7" away from the GDS position) 2MASS

J18302347-1355421  J= 8.28, H= 6.83, K= 5.87, G= 14.36, BP= 18.30, RP= 12.72

Best Regards, Kenta

On 2022/09/27 15:59, Keisuke Isogai wrote:

転送シアmス

-------- Forwarded Message -------- Subject: Re: [vsnet-alert 26940] GDS_J1830235-135539: a new symbiotic nova in Scutum: Date: Mon, 26 Sep 2022 13:12:14 -0300 From: Sebastián Otero sebastian@aavso.org To: vsnet-alert@ooruri.kusastro.kyoto-u.ac.jp, Keisuke Isogai isogai@kusastro.kyoto-u.ac.jp

The Pan-STARRS1 image shows nebulosity around the mira variable so this supports the ID with the symbiotic nova. Also, the other red star is 5" away from this one, so I assume that one is not the star that now has a spectrum.

The statement "The position is identical to that of a known variable star GDS J1830235-135539" is what is still causing confusion. Can you please comment?

Cheers, Sebastian

...

Hello all,

This object really deserves discussion. There hasn't been any comment about its identification. Its GDS coordinates do not match the position of the actual mira variable.

There are two very red objects 3" away from the GDS position (18 30 23.57 -13 55 39.9) but the closest object  in Gaia DR3(1.1" away) is none of them and is not a red star.

18 30 23.63 -13 55 39.2  Gaia DR3 4104372315454096896 - G= 15.29, BP= 15.80, RP= 14.43

Since the GDS variations show the mira-like activity, the catalogue entry should indeed be identified as the red variable, but the light curve and measured position and surely those of a blend.

The same happens in the ATLAS catalogue, the variable entry is ATO J277.5984-13.9275 (LPV - 319/329 d.,  c= 15.32 - 15.63) at 18 30 23.63 -13 55 39.3, which matches Gaia DR3 4104372315454096896's position but the period and type clearly indicates the variable is not that one.

The two red objects in 2MASS are (with their Gaia DR3 J2000.0 positions):

1. 18 30 23.47 -13 55 42.0  (2.7" away from the GDS position) 2MASS

J18302347-1355421  J= 8.28, H= 6.83, K= 5.87, G= 14.36, BP= 18.30, RP= 12.72 2) 18 30 23.54 -13 55 36.9  (2.9" away from the GDS position) 2MASS J18302354-1355369  J= 12.06, H= 9.24, K= 8.14, G= 16.50, BP= 19.13, RP= 15.08

There is a third entry in 2MASS at 18 30 23.54 -13 55 37.8 (2MASS J18302353-1355377  J= 9.54, H= 8.14, K= 7.21) which is actually a blend of the other two (with the flag "photometric confusion")

Star 1) is the actual variable star. It is Gaia DR3 4104372315454847232 (LPV - 322.8 d. G= 12.6 - 14.8). It is also OGLE BLG-LPV-264465 (OGLE BLG575.27.48590), classified as M with a period of 315.3 d., mean Ic = 12.13 and amplitude 2.89 mag.

So we know which is the mira variable. But is is the nova-like object? What about the other red one? And what about the bluer star? There are also two other stars in Gaia DR3 (without color information) which are part of the blend in GDS and ATLAS:

18 30 23.63 -13 55 41.3 (1.7" away from the GDS position) G= 19.80 18 30 23.75 -13 55 39.3 (2.6" away from the GDS position) G= 17.94

I agree that a NC-type brightening and a mira variable look compatible (and make the identification with the bluer or closer objects less likely), but the presence of the other red object casts some doubts about the identification. I think accurate astrometry is needed here to properly identified the outbursting star.

Cheers, Sebastian -- Sebastian Otero VSX Team American Association of Variable Star Observers

“The mission of the AAVSO is to enable anyone, anywhere, to participate in scientific discovery through variable star astronomy”

www.aavso.org

...

GDS_J1830235-135539: a new symbiotic nova in Scutum:

coordinates: 18 30 23.57 -13 55 39.9

ATel #15623: Spectroscopic confirmation of recent brightening of GDS J1830235-135539 as a symbiotic nova and ASASSN-22lk as a large-amplitude dwarf nova https://www.astronomerstelegram.org/?read=15623 VSX:https://www.aavso.org/vsx/index.php?view=detail.top&oid=456166 Light curve and spectrum: www.kusastro.kyoto-u.ac.jp/~kentagch/atel/GDS_J1830235-135539.pdf

Clear skies,

Robert

-- Sebastian Otero VSX Team American Association of Variable Star Observers

“The mission of the AAVSO is to enable anyone, anywhere, to participate in scientific discovery through variable star astronomy”

www.aavso.org