J/MNRAS/546/F2281 Properties of 145 SNe Ia (Hakobyan+, 2026)
Calcium versus silicon ejecta velocities and decline rates in supernovae Ia:
the role of high-velocity features.
Hakobyan A.A., Gevorgyan M.H., Karapetyan A.G., Mamon G.A., Kunth D.,
Adibekyan V., Barkhudaryan L.V.
<Mon. Not. R. Astron. Soc. 546, staf2281 (2026)>
=2026MNRAS.546f2281H 2026MNRAS.546f2281H (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae
Keywords: methods: data analysis - supernovae: individual: Type Ia
Abstract:
Photospheric and high-velocity features (PVFs and HVFs) of SiII
λ6355 and CaII IR3 lines in supernova Ia (SN Ia) spectra
provide insights into ejecta structure, energetics, and circumstellar
interaction, yet their interplay remains poorly understood. We analyse
a representative sample of 145 nearby SNe Ia observed within ±5d of
B-band maximum light, including normal, 91T-, and 91bg-like events
with measured light-curve decline rates (Δm15) and SiII and
CaII line properties from the literature. We model PVF and HVF
velocity distributions using Gaussian Mixture Models, compare SiII and
CaII PVF velocity distributions, assess CaII HVF properties, and test
correlations between SiII PVF velocities and Δm15, with
emphasis on HVF effects. For the first time, we show that the CaII PVF
velocity distribution, measured for the same events at the same phases
as SiII, is predominantly unimodal, in contrast to the well-known
bimodal SiII PVF distribution that supports the
high-velocity/normal-velocity division. This contrast likely reflects
a subclass-dependent formation depth of the CaII line, as supported by
a positive correlation (>3.3σ) between Δm15 and the
velocity offset between CaII and SiII PVFs, particularly in
faster-declining SNe Ia. Importantly, HVFs do not significantly bias
PVF velocity distributions. A significant negative correlation
(>3.3σ) between SiII PVF velocity and Δm15 is found only
for HVF-weak SNe Ia, consistent with more energetic explosions
yielding faster ejecta, while this trend vanishes in HVF-strong
events, likely due to circumstellar interaction. These results
underscore the critical role of HVFs and SN Ia subclass in
interpreting ejecta kinematics in both models and observations.
Description:
The names of all SNe Ia in our sample, their spectroscopic
subclassifications, Δm15 values (with corresponding data
sources), and their redshifts.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
suppl.dat 72 145 Properties of 145 SNe Ia
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See also:
J/MNRAS/451/1973 : Type Ia supernovae high-velocity features (Silverman+, 2015)
Byte-by-byte Description of file: suppl.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- SNname Supernova (SN) name
10- 16 A7 --- SNsubclass SN spectroscopic subclass (1)
18- 36 A19 --- r_SNsubclass Source of SN subclass
38- 41 F4.2 mag dm15 ? SN light curve (LC) decline rate
43- 46 F4.2 mag e_dm15 ? Error of SN LC decline rate
48- 66 A19 --- r_dm15 ? Source of SN LC decline rate
68- 72 F5.3 --- z Redshift of SN
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Note (1): Note on SN subclass as follows:
Ia-norm = normal Type Ia SNe
Ia-91T = overluminous 91T-like SNe
Ia-99aa = overluminous 99aa-like SNe
Ia-91bg = subluminous 91bg-like SNe
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Acknowledgements:
Artur Hakobyan, artur.hakobyan(at)yerphi.am
References:
Hakobyan et al., 2020MNRAS.499.1424H 2020MNRAS.499.1424H, Cat. J/MNRAS/499/1424
Silverman et al., 2015MNRAS.451.1973S 2015MNRAS.451.1973S, Cat. J/MNRAS/451/1973
(End) Artur Hakobyan [YerPHI], Patricia Vannier [CDS] 23-Feb-2026