Early spectroscopy of the classical LMC nova AT2 024fjh
ATel #16575; Steven N. Shore (Univ. Pisa; INAF/OATS),Stephane Charbonnel, Olivier Garde, Pascal Le Du, Lionel Mulato, Thomas Petit (2SPOT, ARAS Group),Hamish Barker, Peter Velez (ARAS Group)
on 6 Apr 2024; 02:26 UT
Credential Certification: S. N. Shore (shore@df.unipi.it)
Subjects: Nova, Transient
We report the early spectroscopic development of the LMC nova AT2 024fjh = ASASSN 24ck, discovered on 2024 Apr.1.05 UT. Our observations have been ongoing since Apr. 3.4 UT (MJD 60403.89) with a variety of telescopes and range of resolutions from 360 - 2700 and exposure times from 2400 to 12000 sec.
The first spectra from Apr. 3 showed only Balmer lines with FWZI ~ 8500+/-200 km/s and FWHM ~ 6000 km/s for H-alpha and a nearly flat profile. A single narrow (800 km/s) emission knot at +2100 km/s (corrected for LMC velocity) was also present on H-beta. These first spectra showed profiles consistent with a high maximum velocity (of order 6000 km/s), geometrically thin shell (around dR/R ~ 0.4) the flat top is typical of such ejecta) with no indication of P Cyg absorption. The spectrum had changed dramatically by Apr. 5.0. A 4800 sec exposure with R ~ 550 and S/N > 50 showed distinct double peak profiles on the Balmer series through H-delta with FWZI ~ 9200 km/s and peak separation of 4600 km/s. We note that the stronger (red) peak coincides with the single feature seen on the previous spectra. He I 4471,5018,5786A was present but weak, showing similar double peak profiles with weaker peak to trough contrast. There is no indication of He II; N III 4638 is also present with a profile similar to that of the Balmer lines in the first spectra. No metal ions, e.., Fe II, were detected. The latest low resolution, high S/N spectrum, from Apr. 6.0 UT, shows further development of the H-alpha and H-beta profiles with the original single peaks now doubled at -2100,-1700,+2000,+2700 km/s; H-gamma and H-delta show only single peaks as do the He I 4471, 5015, 5876, and 7065A lines (He I 6678 is blended in the H-alpha wing). The N III feature remains broad and unstructured. Al III 5706 is probably present. This rapid evolution suggests that the ejecta are aspherical, not yet optically thin, and possibly inclined to the line of sight. The velocity is not exceptional but the development is rapid and the ejecta are likely quite structured. Observations are continuing.
ARAS Spectral Database Novae