6 research outputs found
The Early Light Curve of a Type Ia Supernova 2021hpr in NGC 3147: Progenitor Constraints with the Companion Interaction Model
The progenitor system of Type Ia supernovae (SNe Ia) is expected to be a
close binary system of a carbon/oxygen white dwarf (WD) and a non-degenerate
star or another WD. Here, we present results from a high-cadence monitoring
observation of SN 2021hpr in a spiral galaxy, NGC 3147, and constraints on the
progenitor system based on its early multi-color light curve data. First, we
classify SN 2021hpr as a normal SN Ia from its long-term photometric and
spectroscopic data. More interestingly, we found a significant "early excess"
in the light curve over a simple power-law evolution. The early
light curve evolves from blue to red and blue during the first week. To explain
this, we fitted the early part of -band light curves with a two-component
model of the ejecta-companion interaction and a simple power-law model. The
early excess and its color can be explained by shock cooling emission due to a
companion star having a radius of . We also examined
HST pre-explosion images with no detection of a progenitor candidate,
consistent with the above result. However, we could not detect signs of a
significant amount of the stripped mass from a non-degenerate companion star
( for H emission). The early excess light in
the multi-band light curve supports a non-degenerate companion in the
progenitor system of SN 2021hpr. At the same time, the non-detection of
emission lines opens a door for other methods to explain this event.Comment: 26 pages, 13 figures + appendix, Accepted for publication in Ap
SN 2022vqz: A Peculiar SN 2002es-like Type Ia Supernova with Prominent Early Excess Emission
We present extensive photometric and spectroscopic observations of a peculiar
type Ia supernova (SN Ia) 2022vqz. It shares many similarities with the SN
2002es-like SNe Ia, such as low luminosity (i.e.,
mag) and moderate post-peak decline rate (i.e.,
mag). The nickel mass synthesized in the explosion is estimated as
from the bolometric light curve, which is obviously
lower than normal SNe Ia. SN 2022vqz is also characterized by a slow expanding
ejecta, with Si II velocities persisting around 7000 km s since 16 days
before the peak, which is unique among all known SNe Ia. While all these
properties imply a less energetic thermonuclear explosion that should leave
considerable amount of unburnt materials, however, absent signature of unburnt
carbon in the spectra of SN 2022vqz is puzzling. A prominent early peak is
clearly detected in the - and -band light curves of ATLAS and in the
-band data of ZTF within days after the explosion. Possible mechanisms for
the early peak are discussed, including sub-Chandrasekhar mass double
detonation model and interaction of SN ejecta with circumstellar material
(CSM). We found both models face some difficulties in replicating all aspects
of the observed data. As an alternative, we propose a hybrid CONe white dwarf
as progenitor of SN 2022vqz which can simultaneously reconcile the tension
between low ejecta velocity and absence of carbon. We further discuss the
diversity of 02es-like objects and possible origins of different scenarios.Comment: 24 pages, 12 figures, submitted to MNRA
The optical-gamma correlation in BL Lacertae
We present multifrequency light curves of BL Lacertae from February 2008 to October 2012. Lowenergy data (optical and millimetre) were acquired in the framework of a GASP-WEBT project. High-energy data (ultraviolet, X-ray, and γ-ray) come from observations of the Swift, RXTE, and Fermi satellites. After a period of moderate activity, in May 2011 the source suddenly started to flare at γ and optical-UV frequencies. Activity at millimetre wavelengths and X rays began 3-4 months later. This behaviour offered a good opportunity to study the correlation among flux variability in different bands, in particular between the best-sampled optical and γ-ray light curves. However, even in this fortuitous case, we can only define a general correlation with likely no time lag, but with a lag uncertainty of ±1 day. Indeed, the data reveal a complex relationship between the γ and optical fluxes, which cannot be unveiled because of the small gaps in the sampling of this extremely variable source