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Alert Notice 629: Nova in Sagittarius - N Sgr 2018 = PNV J18040967-1803581

April 11, 2018

Event: Nova in Sagittarius - N Sgr 2018 = PNV J18040967-1803581

Discovered independently by:
- Tadashi Kojima (Tsumagoi, Gunma-ken, Japan; reported to CBAT by S. Nakano)
- Hideo Nishimura (Kakegawa, Shizuoka-ken, Japan; reported to CBAT by S. Nakano)
- Yuji Nakamura (Kameyama, Mie, Japan; reported to CBAT by M. Soma)

Discovery magnitude:
- Kojima: unfiltered CCD magnitude 11.2 on six 5-s frames using a Canon EOS 6D digital camera + 200-mm-f.l. f/3.2 lens
- Nishimura: unfiltered CCD magnitude 11.2 on five 10-s frames using a Canon EOS 6D digital camera + 200-mm-f.l. f/3.2 lens
- Nakamura: unfiltered CCD magnitude 11.3 using a CCD camera with 135-mm-f.l. f/4.0 telephoto lens

Discovery date:
- Kojima: 2018 April 8.723 UT
- Nishimura: 2018 April 8.728 UT
- Nakamura: 2018 April 8.788 UT

Coordinates (2000.0): R.A. 18 04 09.45  Decl. -18 03 55.8  (from VSX)
Spectra: Spectroscopy indicating that PNV J18040967-1803581 is a nova was obtained by H. Akazawa (Funao Astronomical Observatory, Kurashiki, Okayama, Japan) on 2018 April 09.827 UT using a 0.35-m telescope. The spectrum can be viewed at

J. Rupert et al. (ATel #11528) report: "Our spectrum does not appear to resemble that of a Fe II classical nova early in the outburst. However, if the possible progenitor from Pan-STARRS DR1 reported by P. Schmeer on the TOCP [see Note b below] is related to the transient, then the outburst amplitude is about 12 mag and is comparable to some classical novae. However, the low expansion velocities and the numerous sharp absorption lines suggest that this object may be related to the class of luminous red novae such as V4332 Sgr and V838 Mon."

Observing recommendations: Observations of all types (visual, CCD, DSLR, PEP, spectroscopy) and multiple bands as instrumentation permits are strongly encouraged as the nova evolves.

Observations reported to the AAVSO:
2018 Mar. 27.767, <13.2 unfiltered CCD (T. Kojima; via CBET 4506);
30.786, <13 unfiltered CCD (Y. Nakamura; via CBET 4506);
Apr. 7.723, <14 unfiltered CCD (Nishimura; via CBET 4506);
8.927, 11.74 V (V. Agnihotri, Rawatbhata, India; via R. Fidrich to AAVSO Time Sensitive Alerts forum);
8.927, 13.63 B (Agnihotri; via R. Fidrich to AAVSO Time Sensitive Alerts forum);
9.448, 9.5 unfiltered CCD (G. Masi and M. Schwartz, remotely using a 40.6-cm f/3.75 robotic telescope at Tenagra Observatories near Nogales, AZ; via CBET 4506);
9.644, 13.23 B (S. Kiyota; remotely with an iTelescope 0.50-m f/4.5 CDK astrograph at Siding Spring, NSW, Australia; via CBET 4506);
9.644, 11.01 V (Kiyota; via CBET 4506);
9.644, 9.80 Rc (Kiyota; via CBET 4506);
9.644, 8.52 Ic (Kiyota; via CBET 4506);
9.676, 9.7 unfiltered CCD (T. Noguchi, Chiba-ken, Japan; via CBET 4506);
9.7544, 12.99 B +/-0.006 (A. Pearce, Nedlands, W. Australia);
9.7560, 10.83 V +/-0.002 (Pearce);
9.7575, 8.12 I +/-0.001 (Pearce);
9.803, 10.87 V (K. Yoshimoto, Yamaguchi-ken, Japan; remotely with a 0.50-m f/6.8 reflector at Siding Spring; via CBET 4506);
9.803, 9.62 Rc (Yoshimoto; via CBET 4506);
9.803, 8.30 Ic (Yoshimoto; via CBET 4506);
10.1910, <9.1 (C. Adib, Porto Alegre, Brazil);
10.3597, 11.1 (A. Amorim, Florianapolis, Brazil);
10.4194, 11.0 (L. Shotter, Uniontown, PA);
10.75197, 13.004 B +/-0.005 (Pearce);
10.75345, 10.639 V +/-0.002 (Pearce);
10.7653, 11.3 (Pearce);
11.1250, <11.2 (Amorim);

Charts: Charts with a comparison star sequence for N Sgr 2018 may be created using the AAVSO Variable Star Plotter (VSP).

Submit observations: Please submit observations to the AAVSO International Database using the name N SGR 2018. Once a GCVS name is announced in an IAU Circular or CBET, please use that name.

AAVSO Forums: N Sgr 2018 is the topic of the AAVSO Time Sensitive Alerts forum thread
and the AAVSO Novae forum thread

a. Designated PNV J18040967-1803581 when posted to the IAU Central Bureau for Astronomical Telegrams Transient Object Confirmation Page (TOCP). Unless otherwise noted and except for observations reported to the AAVSO, the information in this Alert Notice is taken from IAU CBET 4506.
b. P. Schmeer (Saarbruecken-Bischmisheim, Germany) writes that he has identified a Pan-STARRS DR1 source (magnitude g = 20.95) at position end figures 09.449s, 55.85" as the possible progenitor, adding that he found no previous outbursts or eruptions down to V = 16.1 in images taken by the ASAS-SN Sky Patrol from 2015 February through 2018 March 29.605 UT.

c. Position end figures
 - Kojima (2018 April 8.723 UT): 09.67s, 58.1"
 - Nishimura (2018 April 8.728 UT): 09.46s, 57.3"
 - Nakamura (2018 April 8.788 UT): 09.5s, 04' 01"
 - Masi and Schwartz (2018 April 9.448 UT): 09.46s, 55.6"
 - Noguchi (2018 April 9.676 UT): 09.47s, 55.9"
 - Pearce (2018 April 9.756 UT): 09.46s, 55.7"
 - Yoshimoto (2018 April 9.803 UT): 09.46s, 55.9"
d. Images
 - Nishimura (2018 Apr. 8.728 UT):  
 - Noguchi (2018 April 9.676 UT):
 - Yoshimoto (2018 April 9.803 UT):

Congratulations to Tadashi Kojima, to Hideo Nishimura, and to Yuji Nakamura on their latest discoveries!

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

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