PTF10fqs: A Luminous Red Nova in the Spiral Galaxy Messier 99

The Palomar Transient Factory (PTF) is systematically charting the optical transient and variable sky. A primary science driver of PTF is building a complete inventory of transients in the local Universe (distance less than 200 Mpc). Here, we report the discovery of PTF10fqs, a transient in the luminosity “gap” between novae and supernovae. Located on a spiral arm of Messier 99, PTF 10fqs has a peak luminosity of Mr = -12.3, red color (g-r = 1.0) and is slowly evolving (decayed by 1 mag in 68 days). It has a spectrum dominated by intermediate-width H (930 km/s) and narrow calcium emission lines. The explosion signature (the light curve and spectra) is overall similar to thatof M85OT2006-1, SN2008S, and NGC300OT. The origin of these events is shrouded in mystery and controversy (and in some cases, in dust). PTF10fqs shows some evidence of a broad feature (around 8600A) that may suggest very large velocities (10,000 km/s) in this explosion. Ongoing surveys can be expected to find a few such events per year. Sensitive spectroscopy, infrared monitoring and statistics (e.g. disk versus bulge) will eventually make it possible for astronomers to unravel the nature of these mysterious explosions.

💡 Research Summary

The Palomar Transient Factory (PTF) survey, designed to obtain a complete inventory of optical transients within 200 Mpc, discovered a peculiar event designated PTF10fqs on a spiral arm of the galaxy Messier 99 (NGC 4254). The transient occupies the luminosity “gap” between classical novae (absolute magnitude ≈ ‑9 to ‑10) and ordinary supernovae (≈ ‑17 to ‑19). At peak it reached an absolute r‑band magnitude of Mr = ‑12.3 and displayed a very red color (g‑r ≈ 1.0). Its light curve decayed slowly, fading by roughly one magnitude over 68 days, a rate far slower than that of typical core‑collapse supernovae but comparable to other low‑luminosity, red transients.

Spectroscopic follow‑up revealed intermediate‑width hydrogen Balmer lines (FWHM ≈ 930 km s⁻¹) together with narrow Ca II infrared triplet and forbidden