Faintest of them all : ZTF 21aaoryiz/SN 2021fcg -- Discovery of an extremely low luminosity type Iax supernova

Viraj R. Karambelkar, Mansi M. Kasliwal, Kate Maguire, Shreya G. Anand, Igor Andreoni, Kishalay De, Andrew Drake, Dmitry A. Duev, Matthew J. Graham, Erik C. Kool, Russ R. Laher, Mark R. Magee, Ashish A. Mahabal, Michael S. Medford, Daniel Perley, Mickael Rigault, Ben Rusholme, Steve Schulze, Yashvi Sharma, Jesper Sollerman, Anastasios Tzanidakis, Richard Walters, Yuhan Yao

October 2021

Abstract

We present the discovery of ZTF 21aaoryiz/SN 2021fcg – an extremely low-luminosity Type Iax supernova. SN 2021fcg was discovered by the Zwicky Transient Facility in the star-forming galaxy IC0512 at a distance of $a p p r o x$ 27 Mpc. It reached a peak absolute magnitude of $M{r} =-12.66pm0.20 $m a g, m a k i n g i t t h e l e a s t l u m i n o u s t h e r m o n u c l e a r s u p e r n o v a d i s c o v e r e d t o d a t e . T h e E (B - V) c o n t r i b u t i o n f r o m t h e u n d e r l y i n g h o s t g a l a x y i s u n c o n s t r a i n e d . H o w e v e r, e v e n i f i t w e r e a s l a r g e a s 0.5 m a g, t h e p e a k a b s o l u t e m a g n i t u d e w o u l d b e$ M{r} = -13.78pm0.20 $m a g - s t i l l c o n s i s t e n t w i t h b e i n g t h e l o w e s t l u m i n o s i t y S N . O p t i c a l s p e c t r a o f S N 2021 f c g t a k e n a t 37 a n d 65 d a y s p o s t m a x i m u m s h o w s t r o n g [C a I I], C a I I a n d N a I D e m i s s i o n a n d s e v e r a l w e a k [F e I I] e m i s s i o n l i n e s . T h e [C a I I] e m i s s i o n i n t h e t w o s p e c t r a h a s e x t r e m e l y l o w v e l o c i t i e s o f$ approx 1300 $a n d$ 1000 $k m s$ ^{-1} $r e s p e c t i v e l y . T h e s p e c t r a v e r y c l o s e l y r e s e m b l e t h o s e o f t h e v e r y l o w l u m i n o s i t y T y p e I a x s u p e r n o v a e S N 2008 h a, S N 2010 a e a n d S N 2019 g s c t a k e n a t s i m i l a r p h a s e s . T h e p e a k b o l o m e t r i c l u m i n o s i t y o f S N 2021 f c g i s$ approx2.5^{+1.5}{-0.3}times10^{40} $e r g s$ ^{-1} $w h i c h i s a f a c t o r o f t h r e e l o w e r t h a n t h a t f o r S N 2008 h a . T h e b o l o m e t r i c l i g h t c u r v e o f S N 2021 f c g i s c o n s i s t e n t w i t h a v e r y l o w e j e c t e d n i c k e l m a s s (M$ {rm{Ni}} approx 0.8^{+0.4}{-0.5}times10^{-3} $M$ {odot} $) . T h e l o w l u m i n o s i t y a n d n i c k e l m a s s o f S N 2021 f c g p o s e a c h a l l e n g e t o t h e p i c t u r e t h a t l o w l u m i n o s i t y S N e I a x o r i g i n a t e f r o m d e f l a g r a t i o n s o f n e a r M$ _{rm{ch}}$ hybrid carbon-oxygen-neon white dwarfs. Instead, the merger of a carbon-oxygen and oxygen-neon white dwarf is a promising model to explain SN 2021fcg.

Type

Journal article

http://arxiv.org/abs/2110.04306v1