Long-rising Type II Supernovae in the Zwicky Transient Facility Census of the Local Universe

Long-rising Type II Supernovae in the Zwicky Transient Facility Census of the Local Universe

Recently, a group of astronomers led by Tawny Sit of The Ohio State University (OSU) identified 13 long-evolving Type II SNe (out of a total of 3,444 transients), of which 12 turned out to be new discoveries.

Un equipo internacional de astrónomos informa de la detección de 12 nuevas supernovas de Tipo II de largo crecimiento como parte del Censo del Universo Local (CLU) de la Instalación Transitoria Zwicky (ZTF). El descubrimiento, publicado el 1 de junio en el repositorio de preimpresión arXiv, casi duplica el número de supernovas conocidas de esta subclase.

Las supernovas de tipo II (SNe) son el resultado del colapso rápido y la explosión violenta de estrellas masivas (con masas superiores a 8,0 masas solares). Se distinguen de otros SNe por la presencia de hidrógeno en sus espectros. Según la forma de sus curvas de luz, generalmente se dividen en Tipo IIL y Tipo IIP. El Tipo IIL SNe muestra un declive constante (lineal) después de la explosión, mientras que el Tipo IIP exhibe un período de declive más lento (una meseta) seguido de un decaimiento normal.

An international team of astronomers reports the detection of 12 new, long-growing Type II supernovae as part of the Zwicky Transient Facility (ZTF) Census of the Local Universe (LUC). The discovery, published June 1 on the arXiv preprint repository, nearly doubles the number of known supernovae of this subclass. Type II supernovae (SNe) are the result of the rapid collapse and violent explosion of massive stars (with masses greater than 8.0 solar masses). They are distinguished from other SNe by the presence of hydrogen in their spectra. Based on the shape of their light curves, they are generally divided into Type IIL and Type IIP. Type IIL SNe shows a steady (linear) decline after the explosion, while Type IIP exhibits a slower period of decline (a plateau) followed by normal decay.

Some type II SNS are characterized by unusually long rises to peak, lasting more than 40 days. The observations suggest that, in general, such long-altitude SNe originates from stars that are more compact (with radii below 100 solar radii), massive (with masses around 20 solar masses), and have higher explosion energies. However, although three decades have passed since the discovery of the first high-altitude Type II SNe, designated SN 1987A, only 16 bursts of this subclass have been identified in the local universe.

Recently, a group of astronomers led by Tawny Sit of The Ohio State University (OSU) identified 13 long-evolving Type II SNe (out of a total of 3,444 transients), of which 12 turned out to be new discoveries. The observations were made using the 48-inch Schmidt telescope (P48) at the Palomar Observatory, under the ZTF CLU experiment. The newly discovered Type II SNe have rise times ranging from 67 to 96 days and dome-shaped light curves in r-band photometry. All have maximum absolute magnitudes between −15.6 and −17.5 in the r band, which is consistent with previous studies of the known long-growing Type II SNe. The study found that all 12 SNe have spectra showing broad hydrogen-alpha lines at velocities mostly consistent with those reported by previous Type II Sne observations. In addition, barium (Ba II) spectral lines were detected in nine SNe reported in the article. The results indicate that most of the SNe IIs in the new sample occurred in environments with subsolar metallicities, in faint dwarf galaxies, and on the outskirts of large star-forming galaxies. Two occurred in near-solar or supersolar metallicity settings.

source: https://arxiv.org/abs/2306.01109