Abstract
We presented a detailed analysis of progenitor properties of type IIP supernova 2017eaw in NGC 6946, based on the pre-explosion images and early-time observations obtained immediately after ...the explosion. An unusually red star, with MF814W = −6.9 mag and mF606W − mF814W = 2.9 ± 0.2 mag, can be identified at the SN position in the pre-discovery Hubble Space Telescope (HST) images taken in 2016. The observed spectral energy distribution of this star, covering the wavelength of 0.6–2.0 $\ \mathrm{\mu m}$, matches that of an M4-type red supergiant (RSG) with a temperature of about 3550 K. These results suggest that SN 2017eaw has a RSG progenitor with an initial mass of 12 ± 2 M⊙. The absolute F814W-band magnitude of this progenitor star is found to evolve from −7.2 mag in 2004 to −6.9 mag in 2016. Such a dimming effect is, however, unpredicted for an RSG in its neon/oxygen burning phase when its luminosity should modestly increase. The spectrum of SN 2017eaw taken a few hours after discovery clearly shows a narrow Hα emission feature blueshifted by ∼160 km s−1. This narrow component disappeared in the spectrum taken two days later, suggesting the presence of a circumstellar material (CSM) shell (i.e. at a distance of <2.1–4.3 × 1014 cm). Combining the inferred distance with the expansion velocity of the CSM, we suggest that the progenitor of SN 2017eaw should have experienced violent mass-loss at about 1–2 yr prior to explosion, perhaps invoked by pulsational envelop ejection. This mechanism may help explain its luminosity decline in 2016 as well as the lack of detections of RSGs with relatively higher initial mass as progenitors of SNe IIP.
Stars with initial masses in the range of 8–25 solar masses are thought to end their lives as hydrogen-rich supernovae (SNe II). Based on the pre-explosion images of Hubble space telescope (HST) and ...Spitzer space telescope, we place tight constraints on the progenitor candidate of type IIP SN 2023ixf in Messier 101. Fitting of the spectral energy distribution (SED) of its progenitor with dusty stellar spectral models results in an estimation of the effective temperature as 3091
−258
+422
K. The luminosity is estimated as lg(
L
/
L
⊙
)∼4.83, consistent with a red supergiant (RSG) star with an initial mass of 12
−1
+2
M
⊙
. The derived mass loss rate (6×10
−6
−9×10
−6
M
⊙
yr
−1
) is much lower than that inferred from the flash spectroscopy of the SN, suggesting that the progenitor experienced a sudden increase in mass loss when approaching the final explosion. In the infrared bands, significant deviation from the range of regular RSGs in the color-magnitude diagram and period-luminosity space of the progenitor star indicates enhanced mass loss and dust formation. Combined with new evidence of polarization at the early phases of SN 2023ixf, such a violent mass loss is likely a result of binary interaction.
Abstract Type Icn supernovae (SNe Icn) are a newly detected, rare subtype of interacting stripped-envelope supernovae that show narrow P Cygni lines of highly ionized carbon, oxygen, and neon in ...their early spectra due to the interactions of the SNe ejecta with dense hydrogen- and helium-deficient circumstellar material (CSM). It has been suggested that SNe Icn may have multiple progenitor channels, such as the explosion of carbon-rich Wolf–Rayet stars or the explosion of stripped-envelope SNe, which undergo binary interactions. Among the SNe Icn, SN 2019jc shows unique properties, and previous work inferred that it may stem from the ultrastripped supernova, but other possibilities still exist. In this work, we aim to simulate the light curves from the explosions of oxygen-neon and carbon-oxygen double white dwarf (WD) merger remnants and to further investigate whether the corresponding explosions can appear as some particular SNe Icn. We generate the light curves from the explosive remnants and analyze the influence of different parameters on the light curves, such as the ejecta mass, explosion energy, mass of 56 Ni, and CSM properties. Comparing our results with some SNe Icn, we found that the light curves from the explosions of double WD merger remnants can explain the observable properties of SN 2019jc, from which we infer that this special SN Icn may have a different progenitor. Our results indicate that double WD merger may be an alternative model in producing at least one of the SNe Icn.
Abstract
We present our photometric and spectroscopic observations of the peculiar transient AT2018cow. The multiband photometry covers from peak to ∼70 days, and the spectroscopy ranges from 5 to ...∼50 days. The rapid rise (
t
r
≲ 2.9 days), high luminosity (
M
V
,peak
∼ −20.8 mag), and fast decline after peak make AT2018cow stand out from any other optical transients, whereas we find that its light curves show a high resemblance to those of Type Ibn supernovae. Moreover, the spectral energy distribution remains at a high temperature of ∼14,000 K at
t
> 15 days after discovery. The spectra are featureless in the first 10 days, while some broad emission lines due to H, He, C, and O emerge later, with velocity declining from ∼14,000 to ∼3000 km s
−1
at the end of our observations. Narrow and weak He
I
emission lines emerge in the spectra at
t
> 20 days after discovery. These emission lines are reminiscent of the features seen in interacting supernovae like the Type Ibn and IIn subclasses. We fit the bolometric light curves with a model of circumstellar interaction and radioactive decay of
56
Ni and find a good fit with ejecta mass
M
ej
∼ 3.16
M
⊙
, circumstellar medium (CSM) mass
M
CSM
∼ 0.04
M
⊙
, and ejected
56
Ni mass
M
⊙
. The CSM shell might be formed in an eruptive mass ejection of the progenitor star. Furthermore, the host environment of AT2018cow implies a connection of AT2018cow with massive stars. Combining observational properties and the light-curve fitting results, we conclude that AT2018cow might be a peculiar interacting supernova that originated from a massive star.
We present optical and ultraviolet observations of nearby Type Ic supernova (SN Ic) SN 2017ein, as well as a detailed analysis of its progenitor properties from both the early-time observations and ...the prediscovery Hubble Space Telescope (HST) images. The optical light curves started from within 1 day to ∼275 days after explosion, and optical spectra range from ∼2 days to ∼90 days after explosion. Compared to other normal SNe Ic like SN 2007gr and SN 2013ge, SN 2017ein seems to have more prominent C ii absorption and higher expansion velocities in early phases, suggestive of relatively lower ejecta mass. The earliest photometry obtained for SN 2017ein shows indications of shock cooling. The best fit obtained by including a shock-cooling component gives an estimate of the envelope mass as ∼0.02 M and stellar radius as 8 4 R . Examining the pre-explosion images taken with the HST WFPC2, we find that the SN position coincides with a luminous and blue point-like source, with an extinction-corrected absolute magnitude of MV ∼ −8.2 mag and MI ∼ −7.7 mag. Comparisons of the observations to the theoretical models indicate that the counterpart source was either a single W-R star or a binary whose members had high initial masses, or a young compact star cluster. To further distinguish between different scenarios requires revisiting the site of the progenitor with HST after the SN fades away.
Abstract We present a detailed analysis of the progenitor and its local environment for the recently discovered Type II supernova (SN) 2024ggi at a distance of about 6.7 Mpc, by utilizing the ...pre-explosion images from the Hubble Space Telescope and Spitzer Space Telescope. The progenitor is identified as a red bright variable star, with absolute F814W-band magnitudes being −6.2 mag in 1995 to −7.2 mag in 2003, respectively, consistent with that of a normal red supergiant star. Combining with the historical mid-infrared light curves, a pulsational period of about 379 days can be inferred for the progenitor star. Fitting its spectral energy distribution with stellar spectral models yields the stellar parameters of temperature, radius, and bolometric luminosity as T * = 3290 − 27 + 19 K, R * = 887 − 51 + 60 R ⊙ , and log( L / L ⊙ ) = 4.92 − 0.04 + 0.05 , respectively. The above parameters indicate that the progenitor of SN 2024ggi is consistent with the stellar evolutionary track of a solar-metallicity massive star with an initial mass of 13 − 1 + 1 M ⊙ . Moreover, our analysis indicates a relatively low mass-loss rate (i.e., <3 × 10 −6 M ⊙ yr −1 ) for the progenitor compared to that inferred from flash spectroscopy and X-ray detection (i.e., 10 −2 –10 −5 M ⊙ yr −1 ), implying a significant enhancement in mass loss within a few years prior to the explosion.
Abstract
We present space-based ultraviolet/optical photometry and spectroscopy with the
Swift
Ultra-Violet/Optical Telescope and
Hubble Space Telescope
(
HST
), respectively, along with ground-based ...optical photometry and spectroscopy and near-infrared spectroscopy of supernova SN 2017erp. The optical light curves and spectra are consistent with a normal SN Ia. Compared to previous photometric samples in the near-ultraviolet (NUV), SN 2017erp has UV colors that are redder than NUV-blue SNe Ia corrected to similar optical colors. The chromatic difference between SNe 2011fe and 2017erp is dominated by the intrinsic differences in the UV rather than the expected dust reddening. This chromatic difference is similar to the SALT2 color law, derived from rest-frame ultraviolet photometry of higher redshift SNe Ia. Differentiating between intrinsic UV diversity and dust reddening can have important consequences for determining cosmological distances with rest-frame ultraviolet photometry. This ultraviolet spectroscopic series is the first from
HST
of a normal, albeit reddened, NUV-red SN Ia and is important for analyzing SNe Ia with intrinsically redder NUV colors. We show model comparisons suggesting that metallicity could be the physical difference between NUV-blue and NUV-red SNe Ia, with emission peaks from reverse fluorescence near 3000 Å implying a factor of ∼10 higher metallicity in the upper layers of SN 2017erp compared to SN 2011fe. Metallicity estimates are very model dependent, however, and there are multiple effects in the UV. Further models and UV spectra of SNe Ia are needed to explore the diversity of SNe Ia, which show seemingly independent differences in the near-UV peaks and mid-UV flux levels.
Abstract
ASASSN-14ms may represent the most luminous Type Ibn supernova (SN Ibn) ever detected, with an absolute
U
-band magnitude brighter than −22.0 mag and a total bolometric luminosity >1.0 × 10
...44
erg s
−1
near maximum light. The early-time spectra of this SN are characterized by a blue continuum on which are superimposed narrow P Cygni profile lines of He
i
, suggesting the presence of slowly moving (∼1000 km s
−1
), He-rich circumstellar material (CSM). At 1–2 months after maximum brightness, the He
i
line profiles become only slightly broader, with blueshifted velocities of 2000–3000 km s
−1
, consistent with the CSM shell being continuously accelerated by the SN light and ejecta. Like most SNe Ibn, the light curves of ASASSN-14ms show rapid post-peak evolution, dropping by ∼7 mag in the
V
band over three months. Such a rapid post-peak decline and high luminosity can be explained by interaction between SN ejecta and helium-rich CSM of 0.9
M
⊙
at a distance of ∼10
15
cm. The CSM around ASASSN-14ms is estimated to originate from a pre-explosion event with a mass-loss rate of 6.7
M
⊙
yr
−1
(assuming a velocity of ∼1000 km s
−1
), which is consistent with abundant He-rich material violently ejected during the late Wolf–Rayet (WN9-11 or Opfe) stage. After examining the light curves for a sample of SNe Ibn, we find that the more luminous ones tend to have slower post-peak decline rates, reflecting that the observed differences may arise primarily from discrepancies in the CSM distribution around the massive progenitors.
Abstract
We have conducted photometric and spectroscopic observations of the peculiar Type Ia supernova (SN Ia) 2016ije that was discovered through the Tsinghua-NAOC Transient Survey. This peculiar ...object exploded in the outskirts of a metal-poor, low-surface brightness galaxy (i.e.,
M
g
= −14.5 mag). Our photometric analysis reveals that SN 2016ije is subluminous (
M
B
,
max
= −17.65 ± 0.06 mag) but exhibits relatively broad light curves (Δ
m
15
(
B
) = 1.35 ± 0.14 mag), similar to the behavior of SN 2002es. Our analysis of the bolometric light curve indicates that only 0.14 ± 0.04
M
⊙
of
56
Ni was synthesized in the explosion of SN 2016ije, which suggests a less energetic thermonuclear explosion when compared to normal SNe Ia, and this left a considerable amount of unburned materials in the ejecta. Spectroscopically, SN 2016ije resembles other SN 2002es-like SNe Ia, except that the ejecta velocity inferred from its carbon absorption line (∼4500 km s
−1
) is much lower than that from silicon lines (∼8300 km s
−1
) at around the maximum light. Additionally, most of the absorption lines are broader than other 02es-like SNe Ia. These peculiarities suggest the presence of significant unburned carbon in the inner region and a wide line-forming region along the line of sight. These characteristics suggest that SN 2016ije might originate from the violent merger of a white dwarf binary system, when viewed near an orientation along the iron-group-element cavity caused by the companion star.
Abstract
We present the discovery and studies of the helium-rich, fast-evolving supernova (SN) 2021agco at a distance of ∼40 Mpc. Its early-time flux is found to rise from half peak to the peak of ...−16.06 ± 0.42 mag in the
r
band within
2.4
−
1.0
+
1.5
days, and the post-peak light curves also decline at a much faster pace relative to normal stripped-envelope supernovae (SNe) of Type Ib/Ic. The early-time spectrum of SN 2021agco (
t
≈ 1.0 days after the peak) is characterized by a featureless blue continuum superimposed with a weak emission line of ionized C
iii
, and the subsequent spectra show prominent He
i
lines. Both the photometric and spectroscopic evolution show close resemblances to SN 2019dge, which is believed to have an extremely stripped progenitor. We reproduce the multicolor light curves of SN 2021agco with a model combining shock-cooling emission with
56
Ni decay. The best-fit results give an ejecta mass of ≈0.3
M
⊙
and a synthesized nickel mass of ≈2.2 × 10
−2
M
⊙
. The progenitor is estimated to have an envelope radius of
R
env
≈ 80
R
⊙
and a mass of
M
env
≈ 0.10
M
⊙
. All these suggest that SN 2021agco can be categorized as an ultra-stripped SN Ib, representing the closest object of this rare subtype. This SN is found to explode in the disk of a Sab-type galaxy with an age of ∼10.0 Gyr and low star-forming activity. Compared to normal SNe Ib/c, the host galaxies of SN 2021agco and other ultra-stripped SNe tend to have relatively lower metallicity, which complicates the properties of their progenitor populations.
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