Alert Notice 813: Nova in Sagittarius: N Sgr 2023 = TCP J17562787-1714548

February 21, 2023

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Event: Nova in Sagittarius: N Sgr 2023 = TCP J17562787-1714548

Discovered independently by:
Yukio Sakurai, Mito, Ibaraki-ken, Japan
Hideo Nishimura, Kakegawa, Shizuoka, Japan
Andrew Pearce, Nedlands, Western Australia

Discovery magnitude:
Sakurai - 9.6 unfiltered, on three frames taken using a Nikon D7100+180-mm f/2.8 lens
Nishimura - mag 10.8 unfiltered, on an image taken using a Canon EOS6D + 200mmf/3 lens
Pearce - 10.5 unfiltered, on three images taken using a Canon 800D camera and 85mm f/1.2 lens

Discovery date:
Sakurai - 2023 February 19.823 UT (reported first to CBAT)
Nishimura - 2023 Feb. 19.8044 UT
Pearce - 2023 February 18.834 UT (reported to CBAT February 19.833)

Coordinates (2000.0): R.A. 17 56 27.90  Decl. -17 14 53.6  (from VSX page for N Sgr 2023)

Spectra: Spectra indicating the object to be a He/N-type classical nova were obtained by K. Taguchi (ATel #15911) on 2023 Feb. 20.8719 UT and on Feb. 20.8738 UT, using the integral field spectrograph mounted on the 3.8-m Seimei telescope at Okayama Observatory of Kyoto University.

Other wavelength observations: Observations obtained by Sokolovsky et al. (ATel #15910) with the Swift/XRT and /UVOT instruments on 2023 Feb. 20.58 UT showed x-ray and ultraviolet emission. They state that "It is somewhat unusual for a nova to show shock-powered X-rays visible to Swift/XRT less than two days after eruption. This may suggest that the transient is a very fast nova and/or a nova embedded in the wind of an evolved donor star."

Observing recommendations: Please observe N Sgr 2023 as it continues to evolve, with observations of all types (visual, CCD/CMOS, DSLR, spectroscopy) and multiple bands as instrumentation permits. Frequency of observation depends on the rate of decline, but Dr. Fred Walter (Stony Brook University) recommends a minimum of one observation per night per band.

For spectroscopy, Dr. Walter recommends spectra in blue to observe He II 4686, H-beta, and the Bowen blend (4640A), in addition to H-alpha. Cadence for spectra depends on how fast the nova continues to  evolve, but, he adds, "you can't go wrong with a spectrum every clear night." AAVSO Spectroscopy Section co-leader Lauren Herrington adds: "Slitless spectra would also be valuable; spectra with resolution as low as R=100 are useful to track broad changes in emission as the nova evolves."

Observations reported to the AAVSO:
2023 Feb. 16.839 UT, <11.5 unfiltered DSLR (A. Pearce, Nedlands, W. Australia);
17.816, <12.8 unfiltered DSLR (Y. Sakurai, Mito, Ibaraki-ken, Japan, via TOCP);
17.8492, <15.0: unfiltered DSLR (H. Nishimura, Kakegawa, Shizuoka, Japan, via TOCP);
19.83333, 10.5 (Pearce);
19.834, 11.0: unfiltered DSLR (Pearce);
20.12627, 10.5 (Pearce);
20.36414, 12.066 B +/-0.003 (Pearce, remotely using T72 0.5m f/6.8 reflector + CCD at Rio Hurtado Valley, Chile);
20.36473, 11.390 V +/-0.002 (Pearce, remotely);
20.36659, 11.382 V +/-0.002 (Pearce, remotely);
20.36708, 11.382 V +/-0.004 (Pearce, remotely);
20.36767, 12.081 B +/-0.005 (Pearce, remotely);
20.3575, 11.71 B (S. Kiyota, Kamagaya, Japan, remotely using T72, iTelescope.NET (0.34m F6.8 CDK) + FLI ML-16200 CCD at Deep Sky Chile, Rio Hurtado Valley, Chile, via TOCP);
20.3575, 11.18 V (Kiyota, via TOCP);
20.3575, 9.80 Rc (Kiyota, via TOCP);
20.3575, 9.26 Ic (Kiyota, via TOCP);
20.827, 10.9 unfiltered CCD (T. Noguchi, Katori, Japan, using 0.23-m f/10 Schmidt-Cassegrain + unfiltered CCD (KAF-0261E), via TOCP);
20.84583, 11.5 (Pearce);
21.15972, 11.4 TG +/-0.05 (V. Cseh, Debrecen, Hungary);
21.40207, 12.860 B +/-0.005 (Pearce, remotely using T72 0.5m f/6.8 reflector + CCD at Rio Hurtado Valley, Chile);
21.40293, 12.319 V +/-0.003 (Pearce, remotely);
21.52255, 11.884 V +/-0.002 (F. Romanov, remotely using iTelescope.Net T11 (0.50-m f/6.8 reflector + CCD + f/4.5 focal reducer) in Utah Desert Remote Observatory, Beryl Junction, UT)
21.52360, 12.648 B +/-0.005 (Romanov);
21.52459, 10.715 R +/-0.004 (Romanov);
21.52557, 10.322 I +/-0.009 (Romanov);
21.52660, 11.879 V +/-0.001 (Romanov);
21.52767, 12.625 B +/-0.003 (Romanov);
21.52866, 10.718 R +/-0.003 (Romanov);
21.52963, 10.315 I +/-0.006 (Romanov);

Charts: Charts with comparison stars for N Sgr 2023 may be created using the AAVSO Variable Star Plotter (VSP).

Submit observations: Please submit observations using the name N SGR 2023. When a GCVS name is assigned to this nova, please use it when submitting observations.
 - Submit optical observations to the AAVSO International Database using WebObs.
 - Submit spectra to the AAVSO Spectroscopy Database (AVSpec).

a. Designated TCP J17562787-1714548 when posted to the IAU Central Bureau for Astronomical Telegrams Transient Object Confirmation Page (TOCP).

b. T. Kato (vsnet-alert 27432) identifies the possible progenitor as Gaia DR3 4144602552564272000 (G=18.1, Plx=0.20+/-0.18 mas).

c. Position end figures:
- A. Pearce (2023 02 20.126 UT): 27.90s, 53.7"
- T. Noguchi (2023 02 20.827 UT): 27.91s, 53.5"

d. Images
- H. Nishimura (2023 Feb. 19.8044 UT, discovery image):
- T. Noguchi (2023 Feb. 20.827 UT):
- F. Romanov (2023 Feb. 21.5236 UT):

Congratulations to Yukio Sakurai, Hideo Nishimura, and Andrew Pearce on their independent discoveries!

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

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