Abstract
We present a multiwavelength photometric and spectroscopic analysis of 13 super-Chandrasekhar-mass/2003fg-like Type Ia supernovae (SNe Ia). Nine of these objects were observed by the ...Carnegie Supernova Project. The 2003fg-like SNe have slowly declining light curves (Δ
m
15
(
B
) < 1.3 mag), and peak absolute
B
-band magnitudes of −19 <
M
B
< −21 mag. Many of the 2003fg-like SNe are located in the same part of the luminosity–width relation as normal SNe Ia. In the optical
B
and
V
bands, the 2003fg-like SNe look like normal SNe Ia, but at redder wavelengths they diverge. Unlike other luminous SNe Ia, the 2003fg-like SNe generally have only one
i
-band maximum, which peaks after the epoch of the
B
-band maximum, while their near-IR (NIR) light-curve rise times can be ≳40 days longer than those of normal SNe Ia. They are also at least 1 mag brighter in the NIR bands than normal SNe Ia, peaking above
M
H
= −19 mag, and generally have negative Hubble residuals, which may be the cause of some systematics in dark-energy experiments. Spectroscopically, the 2003fg-like SNe exhibit peculiarities such as unburnt carbon well past maximum light, a large spread (8000–12,000 km s
−1
) in Si
ii
λ
6355 velocities at maximum light with no rapid early velocity decline, and no clear
H
-band break at +10 days. We find that SNe with a larger pseudo-equivalent width of C
ii
at maximum light have lower Si
ii
λ
6355 velocities and more slowly declining light curves. There are also multiple factors that contribute to the peak luminosity of 2003fg-like SNe. The explosion of a C–O degenerate core inside a carbon-rich envelope is consistent with these observations. Such a configuration may come from the core-degenerate scenario.
We present an early-phase g-band light curve and visual-wavelength spectra of the normal Type Ia supernova (SN) 2013gy. The light curve is constructed by determining the appropriate S-corrections to ...transform KAIT natural-system B- and V-band photometry and Carnegie Supernova Project natural-system g-band photometry to the Pan-STARRS1 g-band natural photometric system. A Markov chain Monte Carlo calculation provides a best-fit single power-law function to the first ten epochs of photometry described by an exponent of 2.16+0.06−0.06 2 . 16 − 0.06 + 0.06 $ 2.16^{+0.06}_{-0.06} $ and a time of first light of MJD 56629.4+0.1−0.1 56629 . 4 − 0.1 + 0.1 $ 56629.4^{+0.1}_{-0.1} $ , which is 1.93+0.12−0.13 1 . 93 − 0.13 + 0.12 $ 1.93^{+0.12}_{-0.13} $ days (i.e., < 48 h) before the discovery date (2013 December 4.84 UT) and −19.10+0.12−0.13 − 19 . 10 − 0.13 + 0.12 $ -19.10^{+0.12}_{-0.13} $ days before the time of B-band maximum (MJD 56648.5 ± 0.1). The estimate of the time of first light is consistent with the explosion time inferred from the evolution of the Si IIλ6355 Doppler velocity. Furthermore, discovery photometry and previous nondetection limits enable us to constrain the companion radius down to Rc ≤ 4 R⊙. In addition to our early-time constraints, we used a deep +235 day nebular-phase spectrum from Magellan/IMACS to place a stripped H-mass limit of < 0.018 M⊙. Combined, these limits effectively rule out H-rich nondegenerate companions.
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Abstract We present the second and final release of optical spectroscopy of Type Ia supernovae (SNe Ia) obtained during the first and second phases of the Carnegie Supernova Project (CSP-I and ...CSP-II). The newly released data consist of 148 spectra of 30 SNe Ia observed in the course of CSP-I and 234 spectra of 127 SNe Ia obtained during CSP-II. We also present 216 optical spectra of 46 historical SNe Ia, including 53 spectra of 30 SNe Ia observed by the Calán/Tololo Supernova Survey. We combine these observations with previously published CSP data and publicly available spectra to compile a large sample of measurements of spectroscopic parameters at maximum light, consisting of pseudo-equivalent widths and expansion velocities of selected features for 232 CSP and historical SNe Ia (including more than 1000 spectra). Finally, we review some of the strongest correlations between spectroscopic and photometric properties of SNe Ia. Specifically, we define two samples: one consisting of SNe Ia discovered by targeted searches (most of them CSP-I objects) and the other composed of SNe Ia discovered by untargeted searches, which includes most of the CSP-II objects. The analyzed correlations are similar for both samples. We find a larger incidence of SNe Ia belonging to the cool and broad-line Branch subtypes among the events discovered by targeted searches, shallow-silicon SNe Ia are present with similar frequencies in both samples, while core normal SNe Ia are more frequent in untargeted searches.
The Carnegie Supernova Project II Moriya, T J; Stritzinger, M D; Taddia, F ...
Astronomy and astrophysics (Berlin),
09/2020, Volume:
641
Journal Article
Peer reviewed
Open access
We present optical and near-infrared photometry and spectroscopy of the Type IIn supernova, (SN) 2014ab, obtained by the Carnegie Supernova Project II and initiated immediately after its optical ...discovery. We also study public mid-infrared photometry obtained by the Wide-field Infrared Survey Explorer satellite extending from 56 days prior to the optical discovery to over 1600 days. The light curve of SN 2014ab evolves slowly, while the spectra exhibit strong emission features produced from the interaction between rapidly expanding ejecta and dense circumstellar matter. The light curve and spectral properties are very similar to those of SN 2010jl. The estimated mass-loss rate of the progenitor of SN 2014ab is of the order of 0.1 M⊙ yr−1 under the assumption of spherically symmetric circumstellar matter and steady mass loss. Although the mid-infrared luminosity increases due to emission from dust, which is characterized by a blackbody temperature close to the dust evaporation temperature (∼2000 K), there were no clear signatures of in situ dust formation observed within the cold dense shell located behind the forward shock in SN 2014ab in the early phases. Mid-infrared emission of SN 2014ab may originate from pre-existing dust located within dense circumstellar matter that is heated by the SN shock or shock-driven radiation. Finally, for the benefit of the community, we also present five near-infrared spectra of SN 2010jl obtained between 450 to 1300 days post-discovery in the appendix.
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The Carnegie Supernova Project II Taddia, F; Stritzinger, M D; Fransson, C ...
Astronomy and astrophysics (Berlin),
06/2020, Volume:
638
Journal Article
Peer reviewed
Open access
We present ultra-violet (UV) to mid-infrared (MIR) observations of the long-lasting Type IIn supernova (SN) 2013L obtained by the Carnegie Supernova Project II beginning two days after discovery and ...extending until +887 days (d). The SN reached a peak r-band absolute magnitude of ≈−19 mag and an even brighter UV peak, and its light curve evolution resembles that of SN 1988Z. The spectra of SN 2013L are dominated by hydrogen emission features, characterized by three components attributed to different emission regions. A unique feature of this Type IIn SN is that, apart from the first epochs, the blue shifted line profile is dominated by the macroscopic velocity of the expanding shock wave of the SN. We are therefore able to trace the evolution of the shock velocity in the dense and partially opaque circumstellar medium (CSM), from ∼4800 km s−1 at +48 d, decreasing as t−0.23 to ∼2700 km s−1 after a year. We performed spectral modeling of both the broad- and intermediate-velocity components of the Hα line profile. The high-velocity component is consistent with emission from a radially thin, spherical shell located behind the expanding shock with emission wings broadened by electron scattering. We propose that the intermediate component originates from preionized gas from the unshocked dense CSM with the same velocity as the narrow component, ∼100 km s−1, but also that it is broadened by electron scattering. These features provide direct information about the shock structure, which is consistent with model calculations. The spectra exhibit broad O I and O I lines that emerge at ≳+144 d and broad Ca II features. The spectral continua and the spectral energy distributions (SEDs) of SN 2013L after +132 d are well reproduced by a two-component black-body (BB) model; one component represents emitting material with a temperature between 5 × 103 and 1.5 × 104 K (hot component) and the second component is characterized by a temperature around 1–1.5 × 103 K (warm component). The warm component dominates the emission at very late epochs (≳+400 d), as is evident from both the last near infrared (NIR) spectrum and MIR observations obtained with the Spitzer Space Telescope. Using the BB fit to the SEDs, we constructed a bolometric light curve that was modeled together with the unshocked CSM velocity and the shock velocity derived from the Hα line modeling. The circumstellar-interaction model of the bolometric light curve reveals a mass-loss rate history with large values (1.7 × 10−2 − 0.15 M⊙ yr−1) over the ∼25−40 years before explosion, depending on the radiative efficiency and anisotropies in the CSM. The drop in the light curve at ∼350 days and the presence of electron scattering wings at late epochs indicate an anisotropic CSM. The mass-loss rate values and the unshocked-CSM velocity are consistent with the characteristics of a massive star, such as a luminous blue variable (LBV) undergoing strong eruptions, similar to η Carinae. Our analysis also suggests a scenario where pre-existing dust grains have a distribution that is characterized by a small covering factor.
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The Carnegie Supernova Project I Stritzinger, M. D.; Anderson, J. P.; Contreras, C. ...
Astronomy and astrophysics (Berlin),
2018, 20180101, Volume:
609
Journal Article
Peer reviewed
Open access
The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated supernova follow-up program based at the Las Campanas Observatory that collected science data of young, low-redshift ...supernovae between 2004 and 2009. Presented in this paper is the CSP-I photometric data release of low-redshift stripped-envelope core-collapse supernovae. The data consist of optical (uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared (YJH) photometry. Twenty objects have optical pre-maximum coverage with a subset of 12 beginning at least five days prior to the epoch of B-band maximum brightness. In the near-infrared, 17 objects have pre-maximum observations with a subset of 14 beginning at least five days prior to the epoch of J-band maximum brightness. Analysis of this photometric data release is presented in companion papers focusing on techniques to estimate host-galaxy extinction and the light-curve and progenitor star properties of the sample. The analysis of an accompanying visual-wavelength spectroscopy sample of ~150 spectra will be the subject of a future paper.
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The Carnegie Supernova Project I Stritzinger, M. D.; Anderson, J. P.; Contreras, C. ...
Astronomy and astrophysics (Berlin),
2018, Volume:
609
Journal Article
Peer reviewed
Open access
The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated supernova follow-up program based at the Las Campanas Observatory that collected science data of young, low-redshift ...supernovae between 2004 and 2009. Presented in this paper is the CSP-I photometric data release of low-redshift stripped-envelope core-collapse supernovae. The data consist of optical ( uBgVri ) photometry of 34 objects, with a subset of 26 having near-infrared ( YJH ) photometry. Twenty objects have optical pre-maximum coverage with a subset of 12 beginning at least five days prior to the epoch of B -band maximum brightness. In the near-infrared, 17 objects have pre-maximum observations with a subset of 14 beginning at least five days prior to the epoch of J -band maximum brightness. Analysis of this photometric data release is presented in companion papers focusing on techniques to estimate host-galaxy extinction and the light-curve and progenitor star properties of the sample. The analysis of an accompanying visual-wavelength spectroscopy sample of ~150 spectra will be the subject of a future paper.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
The Carnegie Supernova Project II Taddia, F.; Stritzinger, M. D.; Fransson, C. ...
Astronomy and astrophysics (Berlin),
06/2020, Volume:
638
Journal Article
Peer reviewed
Open access
We present ultra-violet (UV) to mid-infrared (MIR) observations of the long-lasting Type IIn supernova (SN) 2013L obtained by the Carnegie Supernova Project II beginning two days after discovery and ...extending until +887 days (d). The SN reached a peak
r
-band absolute magnitude of ≈−19 mag and an even brighter UV peak, and its light curve evolution resembles that of SN 1988Z. The spectra of SN 2013L are dominated by hydrogen emission features, characterized by three components attributed to different emission regions. A unique feature of this Type IIn SN is that, apart from the first epochs, the blue shifted line profile is dominated by the macroscopic velocity of the expanding shock wave of the SN. We are therefore able to trace the evolution of the shock velocity in the dense and partially opaque circumstellar medium (CSM), from ∼4800 km s
−1
at +48 d, decreasing as
t
−0.23
to ∼2700 km s
−1
after a year. We performed spectral modeling of both the broad- and intermediate-velocity components of the H
α
line profile. The high-velocity component is consistent with emission from a radially thin, spherical shell located behind the expanding shock with emission wings broadened by electron scattering. We propose that the intermediate component originates from preionized gas from the unshocked dense CSM with the same velocity as the narrow component, ∼100 km s
−1
, but also that it is broadened by electron scattering. These features provide direct information about the shock structure, which is consistent with model calculations. The spectra exhibit broad O
I
and O
I
lines that emerge at ≳+144 d and broad Ca
II
features. The spectral continua and the spectral energy distributions (SEDs) of SN 2013L after +132 d are well reproduced by a two-component black-body (BB) model; one component represents emitting material with a temperature between 5 × 10
3
and 1.5 × 10
4
K (hot component) and the second component is characterized by a temperature around 1–1.5 × 10
3
K (warm component). The warm component dominates the emission at very late epochs (≳+400 d), as is evident from both the last near infrared (NIR) spectrum and MIR observations obtained with the
Spitzer
Space Telescope. Using the BB fit to the SEDs, we constructed a bolometric light curve that was modeled together with the unshocked CSM velocity and the shock velocity derived from the H
α
line modeling. The circumstellar-interaction model of the bolometric light curve reveals a mass-loss rate history with large values (1.7 × 10
−2
− 0.15
M
⊙
yr
−1
) over the ∼25−40 years before explosion, depending on the radiative efficiency and anisotropies in the CSM. The drop in the light curve at ∼350 days and the presence of electron scattering wings at late epochs indicate an anisotropic CSM. The mass-loss rate values and the unshocked-CSM velocity are consistent with the characteristics of a massive star, such as a luminous blue variable (LBV) undergoing strong eruptions, similar to
η
Carinae. Our analysis also suggests a scenario where pre-existing dust grains have a distribution that is characterized by a small covering factor.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
The Carnegie Supernova Project II Moriya, T. J.; Stritzinger, M. D.; Taddia, F. ...
Astronomy and astrophysics (Berlin),
09/2020, Volume:
641
Journal Article
Peer reviewed
Open access
We present optical and near-infrared photometry and spectroscopy of the Type IIn supernova, (SN) 2014ab, obtained by the Carnegie Supernova Project II and initiated immediately after its optical ...discovery. We also study public mid-infrared photometry obtained by the Wide-field Infrared Survey Explorer satellite extending from 56 days prior to the optical discovery to over 1600 days. The light curve of SN 2014ab evolves slowly, while the spectra exhibit strong emission features produced from the interaction between rapidly expanding ejecta and dense circumstellar matter. The light curve and spectral properties are very similar to those of SN 2010jl. The estimated mass-loss rate of the progenitor of SN 2014ab is of the order of 0.1
M
⊙
yr
−1
under the assumption of spherically symmetric circumstellar matter and steady mass loss. Although the mid-infrared luminosity increases due to emission from dust, which is characterized by a blackbody temperature close to the dust evaporation temperature (∼2000 K), there were no clear signatures of in situ dust formation observed within the cold dense shell located behind the forward shock in SN 2014ab in the early phases. Mid-infrared emission of SN 2014ab may originate from pre-existing dust located within dense circumstellar matter that is heated by the SN shock or shock-driven radiation. Finally, for the benefit of the community, we also present five near-infrared spectra of SN 2010jl obtained between 450 to 1300 days post-discovery in the appendix.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
We present the second and final release of optical spectroscopy of Type Ia Supernovae (SNe Ia) obtained during the first and second phases of the Carnegie Supernova Project (CSP-I and CSP-II). The ...newly released data consist of 148 spectra of 30 SNe Ia observed in the course of the CSP-I, and 234 spectra of 127 SNe Ia obtained during the CSP-II. We also present 216 optical spectra of 46 historical SNe Ia, including 53 spectra of 30 SNe Ia observed by the Calán/Tololo Supernova Survey. We combine these observations with previously published CSP data and publicly-available spectra to compile a large sample of measurements of spectroscopic parameters at maximum light, consisting of pseudo-equivalent widths and expansion velocities of selected features, for 232 CSP and historical SNe Ia (including more than 1000 spectra). Finally, we review some of the strongest correlations between spectroscopic and photometric properties of SNe Ia. Specifically, we define two samples: one consisting of SNe Ia discovered by targeted searches (most of them CSP-I objects) and the other composed of SNe Ia discovered by untargeted searches, which includes most of the CSP-II objects. The analysed correlations are similar for both samples. We find a larger incidence of SNe Ia belonging to the Cool (CL)and Broad Line (BL) Branch subtypes among the events discovered by targeted searches, Shallow Silicon (SS) SNe Ia are present with similar frequencies in both samples, while Core Normal (CN) SNe Ia are more frequent in untargeted searches.
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