Cerium Features in Kilonova Near-infrared Spectra: Implication from a Chemically Peculiar Star
Abstract
Observations of the kilonova from the neutron star merger event GW170817 opened a way to study r-process nucleosynthesis directly using neutron star mergers. It is, however, challenging to identify individual elements in kilonova spectra due to a lack of complete atomic data, in particular at near-infrared (NIR) wavelengths. In this paper, we demonstrate that spectra of chemically peculiar stars with enhanced heavy-element abundances can provide us with an excellent astrophysical laboratory for kilonova spectra. We show that the photosphere of the late B-type, chemically peculiar star HR 465 has similar lanthanide abundances and ionization degrees with those in the line-forming region in a kilonova at ~2.5 days after the merger. The NIR spectrum of HR 465 taken with Subaru/IRD indicates that Ce III lines give the strongest absorption feature around 16000 Å and there are no other comparably strong transitions around these lines. The Ce III lines nicely match with the broad absorption feature at 14500 Å observed in GW170817 with a blueshift of v = 0.1 c, which supports recent identification of this feature as Ce III by Domoto et al.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2023
- DOI:
- 10.3847/1538-4357/acdc95
- arXiv:
- arXiv:2306.04697
- Bibcode:
- 2023ApJ...953...17T
- Keywords:
-
- Neutron stars;
- R-process;
- Transient sources;
- Stellar spectral lines;
- 1108;
- 1324;
- 1851;
- 1630;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 12 pages, 6 figures, accepted for publication in ApJ