Possible Nova in Vel

[Francois Teyssier]

A bright transcient has been detected in Vela

http://www.cbat.eps.harvard.edu/unconf/ ... 31109.html

The target was detected in gamma:

https://www.astronomerstelegram.org/?read=17252

An identification as dwarf nova of type SU UMa (outburst and super outbursts) was proposed,
based on an historical study of OGLE data:

https://www.astronomerstelegram.org/?read=17253

But, the spectra are very far to be consistent with this classification.

The object is atypical and more data (photometry and spectroscopy) are needed for a *serious* evaluation.

Spectra: https://aras-database.github.io/databas ... l2025.html

[2SPOT]

A fast change in the profil of this Nova in less than 24h




And an Atel :

https://www.astronomerstelegram.org/?read=17256

[Francois Teyssier]

Optical spectroscopy of V572 Vel: Not obviously a classical nova

ATel #17256; Steve Shore (Univ. Pisa, INAF-OATS), Olivier Garde, Stephane Charbonnel, Lionel Mulato , Pascal Le Dû, Thomas Petit (2SPOT), Paul Luckas (Univ. Western Australia, ARAS), Francois Teyssier (ARAS), Peter Velez (ARAS)
on 30 Jun 2025; 02:12 UT
Distributed as an Instant Email Notice Transients
Credential Certification: S. N. Shore (shore@df.unipi.it)

Subjects: Optical, Nova, Transient

Following the announcement of the outburst of V572 Vel ( (CBET #5574), a campaign of echelle resolution (R ~ 11000) spectroscopy with small aperture telescopes of this reputed nova began on 2025 Jun 26.4 (MJD 60852) and are continuing.

The interstellar Na I D and Ca II H and K lines have V_LSR ~ +37 km/s.

A weak (~ 10%) absorption trough appears on e.g., Na I D2, Ca II K, Si II 6347 at v_Hel ~ -250 km/s, the same as a 40% absorption feature on Halpha (for which the 20% emission extends to +440 km/s).
All Balmer lines to H epsilon have the same absorption component. The neutral and singly ionized metals and Balmer lines all show the same absorption component. The velocity increased to -300 km/s on MJD 60854 with an increase in the complexity of the absorption spectrum.

Na I D1 and D2 showed narrow (< 100 km/s) absorption components at vrad ~ -320 km/s, Halpha showed a 60% absorption at -280 km/s with only a 10% emission feature.

The Halpha profile displayed an abrupt, dramatic change on MJD 60855, showing an emission component at 1.5 times the continuum extending from about -1200 km/s to +2700 km/s but with absorption (now only to the continuum level) at -280 km/s. The absorption profile also remained unchanged despite the intense emission.

The Hbeta and Hgamma profiles were extremely complex, with overlapping metallic absorption on the red wing but the same absorption component at -300 km/s and a new feature at around -1200 km/s. The Na I D line now showed an 10% emission component extending to about +1500 km/s. Si II 6347/70, Ca II K, and Fe II 5018 lines displayed two discrete absorption components at -1200 km/s like the Balmer lines and a weaker one at -400 km/s with no emission component.
There was no evidence of He I, C II, or either [O I] 6300/64 or [Ca II] 7291/7321, or any forbidden metal line transitions.

There appear to be two distinct regions, one whose physical properties resemble a classical shell star or supergiant and the other, at high velocity, is a rapidly evolving emission line region that may be orthogonal to the absorber, perhaps as in the merger system V1309 Sco.

We note that the strong emission lines only appeared between Jun 28.4 and Jun 28.9, one day after the significant Fermi detection (ATel#17252).

AAVSO visual lightcurve:

V572Vel.PNG (10.23 KiB) Viewed 16 times