Deep Sky Object in Spring
Supernova 2023ixf in M101


Date & Time: (Left) Dec 24 2022, from 27:53 to 28:33 JST(+0900), 8min.×6shots
(Right) Jun 17 2023, from 22:37 to 23:21 JST(+0900), 6min.×8shots
Optical: TAKAHASHI 16cm(6.3") epsilon (f=530mm, F3.3)
with IDAS LPS-D1 Light-pollution suppression filter
Auto-guided with TAKAHASHI JP Equatorial+SBIG STV
CMOS Camera: ZWO ASI2600MC Pro (Cooled temp.: -25°C(Dec 24), -15°C(Jun 17))
Location: Ooizumi, Hokuto city, Yamanashi pref.

Camera Settings: Recording format...16bit FITS, converted to 16bit TIFF(6248×4176)
Device Size...23.5×15.7mm, Gain...100


On May 19, 2023, Mr. Kohichi Itagaki, a prominent supernova hunter from Japan, discovered a supernova with a magnitude of 14.9 in M101. It has been confirmed that the supernova is classified as Type II caused by the gravitational collapse of a massive star. Observations of changes in brightness, spectrum, and other properties have been made at observatories worldwide. It was also confirmed that the supernova appeared two days prior, on May 17, with a brightness of 15.9 magnitude.
This image is a comparison of M101 taken on Dec 24, 2022, before the appearance of the supernova, and approximately one month later on Jun 17, 2023, after its appearance. The supernova SN2023ixf appeared within one of the arms located about 4.3 arcminutes southeast of the central nucleus. It is situated right next to NGC5461, an Hα emission nebula within M101. At that time, the brightness of the supernova was approximately 12th magnitude, making it easily observable with a small telescope. This is the first supernova to appear in such proximity to Earth since SN2014J, which appeared in M82 in January 2014.


Spectral profile of SN2023ixf (Jun 17 & Jul 16, 2023)

Date & Time: Jun 17 2023, from 20:42 to 20:52 JST(+0900), 5min.×2shot
Jul 16 2023, from 20:36 to 20:46 JST(+0900), 5min.×2shot
Optical: Meade 25cm(10") Schmidt Cassegrain (f=2500mm, F10.0)
with SBIG DSS7 Spectrometer
Auto-guided with Meade LX200 Equatorial & Lacerta M-GEN
Cooled CCD Camera: SBIG ST-402ME (Temp.: -10°C(Jun 17), -7°C(Jul 16))
Location: Ooizumi, Hokuto city, Yamanashi pref.

Upper strip: taken spectrogram, Lower strip: stretched 4-pixel-width & pseudo-colored image


Absorption lines on Jun 17, 2023
Absorption lineHβC IVC II
Observed WL, λm4775 Å5739 Å5078 Å
 WL in literature, λ04861 Å5812 Å5145 Å
Blue shift, z1.77×10-21.26×10-21.30×10-2
Closing velocity, V(km/s)5.26×1033.74×1033.88×103
Expanding velocity, V'(km/s)5.62×1034.10×1034.24×103

Absorption lines on Jul 16, 2023
Absorption lineHβC IVC IIN II
Observed WL, λm4791 Å5785 Å5101 Å4954 Å
 WL in literature, λ04861 Å5812 Å5145 Å5005 Å
Blue shift, z1.44×10-24.65×10-38.55×10-31.02×10-2
Closing velocity, V(km/s)4.29×1031.39×1032.55×1033.04×103
Expanding velocity, V'(km/s)4.65×1031.75×1032.91×1033.40×103

  z= (λ0-λm)/λ0
  V= c*((1+z)2-1)/((1+z)2+1)
  V'= V + 360 km/s (Recession velocity of M101)
This is the comparison of spectral images and intensity distributions of SN2023ixf observed on June 17 and July 16, 2023, approximately one and two months after its appearance. During May 2023, numerous emission spectral lines of light elements such as hydrogen, nitrogen, and carbon were observed. However, at the time of this capture, the supernova's expelled stellar atmosphere had spread significantly, leading to the residual light of only the Hƒ¿ emission line being detectable. Additionally, broad absorption lines of Hβ, ionized carbon (C II and C IV), and ionized nitrogen (N II, detected only Jul 16) were observed, albeit indistinctly.
From the observed wavelengths of the absorption lines in the supernova's spectrum, it is possible to estimate the line-of-sight velocity (i.e., expansion velocity) associated with the explosion. The table on the right shows the expansion velocities derived from the blue-shifts of the minimum wavelengths of three absorption lines. It should be noted that the Hα line is excluded from the analysis due to the broadening of the emission line, which hinders accurate wavelength determination. The recession velocity of M101 itself due to cosmic expansion is approximately 360 km/s, and accounting for that, the estimated average expansion velocity (V') of the supernova explosion ranges approximately 4600 and 3200 km/s on Jun 16 and Jul 17, respectively. It is confirmed that the blast wave is decelerating as the days pass.
⇒ Back to M101




M94
NGC5866(M102)

Copyright(c) 2023 by Naoyuki Kurita, All rights reserved.
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