Optical Photometry and Spectroscopy of Nova Sco 2024 (V1723 Sco)

ATel #16454; Gesesew R. Habtie (S. N. Bose National Center for Basic Sciences), R. Das (S. N. Bose National Center for Basic Sciences)
on 16 Feb 2024; 19:04 UT
Credential Certification: Gesesew Reta Habtie (gesesew@bose.res.in)

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Nova Sco 2024 was independently discovered by Andrew Pearce (Nedlands, W. Australia) on 2024 Feb 8.827 UT at magnitude 7.8 and Yukio Sakurai (Mito, Japan) on Feb. 9.836 UT at 7.1 mag (CBET #5346, Atel #16440, #16441, #16442, #16444). It is located at R.A. 17 26 18.13, Decl. -38 09 35.4. We analyzed AAVSO's BVRI and Vis photometric data to determine the characteristic time of Nova Sco 2024. At the time of discovery, the nova was in its rising phase. On February 10.79, 2024 UT, it reached its maximum brightness in the V band, with a magnitude of 6.77 +/- 0.001. Then, on February 14th, it decreased to 8.675 +/- 0.07 mag, which is approximately 1.9 mag less than the maximum. However, it brightened again to 8.23 and then to 8.41 mag on days 5 and 6 respectively, inferring that the nova has not yet reached its t2 value. We also analyzed two spectra available in the ARAS database, both of which were captured by 2SPOT on 2024 February 11.368 and 12.362 UT. From H-alpha and H-beta lines, we determined that the Nova Sco 2024 shell is expanding at a velocity of around 3200 +/- 200 and 1800 +/- 100 km/s, respectively. Additionally, we observed that the peak broad component of both the H-alpha and H-beta lines has shifted blue-wards relative to their rest frame by -294 and -330 km/s, respectively. Over time, the shift in both lines exhibited an increment. Furthermore, the central maxima of the He I 5876 Ang emission line, which is dominated by very deep adjacent absorption (Na D1 and D2) lines, displayed a shift red-wards by about 933 +/- 50 km/s relative to the rest frame of the original line. On the contrary, both the absorption lines (Na D1 and D2; ATel #16442) exhibited a blue shift of -28.5 +/- 2 and -24.2 +/- 2 km/s on February 11.368 UT, and -28.1 +/- 2 and -30.7 +/- 2 km/s on February 12.362 UT, respectively, relative to their own rest frame. On the red side of the H-alpha profile (at 6613 Å), a clearly visible absorption line appeared, possibly indicating a diffuse inter-stellar feature. The line was present in the both of the spectra, with an average equivalent width of ~0.248 Ang and a FWHM of 59.7 km/s. A similar phenomenon occurred in the case of V1674 Her (Atel #14740). Acknowledgments: We acknowledge the ARAS database and AAVSO for granting us access to their data. Moreover, we express our gratitude to F. Teyssier for coordinating the ARAS database and to 2SPOT (https://2spot.org/FR/).