Discovered by LAST on 2026-03-17 23:39:59.904 at 19.97 ABMag (TNS N°294890) RAPAS ProAm network monitors the rise of SN 2026fvx from 2026-03-19 up to now and will follow it later on. It is classified as a Ia supernova at z=0.004846 (Konno et al. AstroNote 2026-75). During this period, 11 telescopes located in France, using the set of RAPAS G, Gbp and Grp filters meeting the three Gaia G, Gbp and Grp photometric band specifications, collected more than 50 measurements in 1, 2 or the 3 Gaia bands. The photometric consistency was ensured by reducing each frame with the corresponding Gaia DR3 reference catalog for G, Gbp and Grp bands.
The multi-band light curve shows a peak around 2026-04-04 at 12.8 G magnitude while the Color Index Gbp-Grp decreased from 0.5 to 0 showing the rising temperature. Since then the light curve seems to stabilize up to 2026-04-10, then started to fade.
We measured the following envelope’s expansion velocity from the SiII 635.5nm absorption (spectra obtained by Christian Buil), and found a decrease coherent with the initial velocity obtained by Konno et al. of 17000 km/s around March 18th :
2026-03-27.882 -10321km/s
2026-04-05.882 -9621km/s
2026-04-15.891 -9300km/s
Detailed light curves and data are presented on the RAPAS web page and Astro-COLIBRI web page on the following links :
https://rapas.imcce.fr/SN2026fvx-lightcurve.jpg
https://rapas.imcce.fr/SN2026fvx-mag-vs-bp-rp-index.jpg
https://rapas.imcce.fr/SN2026fvx_RAPAS.csv
https://rapas.imcce.fr/SN2026fvx-SED-20260327.png
https://rapas.imcce.fr/SN2026fvx-SED-20260405.jpg
https://rapas.imcce.fr/SN2026fvx-SED-20260407.jpg
https://rapas.imcce.fr/SN2026fvx-SED-20260415.png
https://rapas.imcce.fr/SN2026fvx-SED-20260415b.png
Further details and the full dataset are accessible to registered users of the RAPAS Spreadsheets platform.
Acknowledgements :
RAPAS ( https://gemini.obspm.fr/20220101-rapas/ ) is a ProAm collaboration created by T. Midavaine (SAF), W. Thuillot (LTE, Obs. de Paris-PSL) and M. Dennefeld (IAP/CNRS and Sorbonne Univ.) and funded by the Paris Observatory under API ProAm of the Scientific Council. It aims at homogenizing observing procedures and filters, and is delivering to a network of amateur observatories a set of 3 filters which have been chosen to meet the Gaia G, Gbp and Grp spectral bands. This network produces data on astrophysical alerts delivered by various Alert systems (Gaia Alerts, Atlas, ZTF, etc…) and collected by Astro-COLIBRI ( https://astro-colibri.science). This network is similarly progressing towards an homogeneous spectroscopic equipment to deliver SED.
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