SN 393

Supernova SN 393

The Wěi asterism appears in the lower half of the Scorpius constellation
Event type	Supernova
Type II/Ib[1]
Date	27 February− 28 March 393 22 October− 19 November 393 CE[2]
Constellation	Scorpius
Right ascension	17h 14m [3]
Declination	−39.8°[3]
Epoch	J2000
Galactic coordinates	G347.4−00.6°[3]
Distance	1 kpc (3×10^3 ly)[4]
Remnant	Shell
Host	Milky Way
Peak apparent magnitude	−1[5]
Other designations	SN 393
Preceded by	SN 386
Followed by	SN 1006
[edit on Wikidata]

SN 393 is the modern designation for a probable supernova that was reported by the Chinese in the year 393 CE. An extracted record of this astronomical event was translated into English as follows:

A

Song Shu^[2]

The second lunar month mentioned in the record corresponds to the period 27 February to 28 March 393 CE, while the ninth lunar month ran from 22 October to 19 November 393 CE. The bowl-shaped asterism named Wěi is formed by the tail of the modern constellation Scorpius. This asterism consists of the stars in Scorpius designated ε, μ, ζ, η, θ, ι, κ, λ and ν. The guest star reached an estimated apparent magnitude of −1 and was visible for about eight months before fading from sight,^[5] whose lengthy duration suggests the source was a supernova.^[6] However, a classical nova is not excluded as possibility.^[7][6]

Suggested as supernova

Before 1975, the observation made by the Chinese between February and March 393 CE was considered to be likely a bright nova with a secondary maximum.^[6] At the time, there were only seven possible candidate supernova remnants near where SN 393 was observed. Assuming maximum –1 magnitude occurred close to 10,000 pc (33,000 ly) away, this immediately ruled out four possible candidates. Another discounted remnant was G350.0-1.8, as the expectant expansion rate indicated the supernova occurred around 8,000 years ago. Of the two remaining sources, G348.5+0.1 and G348.7+0.3, were both at the required 10,000 pc. distance and also each had estimated ages of 1,500 years.^[5] If true, it seems unlikely such supernovae would be visible to the naked eye over eight months, especially because they occurred close to a particularly dusty part of the galactic plane.^[2]

Stephenson^[8] and his colleagues preferred the supernova suggestion. In their most recent book and subsequent articles, Stephenson and Green^[9] refer to the suggestion by Wang et al. (1997)^[10] who suggested G347.3–00.5.

Suggested as classical nova

The decline time of classical novae is measured typically as the duration of decline by 3 mag from peak. This so-called t₃ time ranges from typical 25–30 days (a month or two) for fast novae up to ten months for the slowest known classical novae (and even longer for diffusion induced novae).^[11][12] Thus, this historical transient could easily have been caused by a (slow) classical nova: postulating a peak brightness of (at least) 2 mag for the historical sighting and vanishing to invisibility (>5 mag) within 8 months, it could be a slow nova. The brighter the peak, the faster the nova: if the peak was −1 mag (like Sirius) or −4 (like Venus) and declined to >5 mag within eight months (6 mag or more in eight months) it could also refer to a moderately fast nova. Possible (and certainly not the only) candidates in the Chinese constellation of Wei are according to:^[7]

Possible confirmation of SN 393

During 1996, the

Supernova remnant RX J1713.7-3946 is consistent with type II or type Ib supernovae. SN 393's progenitor had a mass of at least 15 solar masses, whose destruction generated energies of about 1.3 × 10⁵¹ erg, with three solar masses of material ejected into the surrounding interstellar medium.^[1]

See also

• Chinese astronomy
• Chinese constellations

References