| 1. |
- Biswas, Rahul, et al.
(author)
-
Two c's in a pod : cosmology-independent measurement of the Type Ia supernova colour-luminosity relation with a sibling pair
- 2022
-
In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 509:4, s. 5340-5356
-
Journal article (peer-reviewed)abstract
- Using Zwicky Transient Facility (ZTF) observations, we identify a pair of ‘sibling’ Type Ia supernovae (SNe Ia), i.e. hosted by the same galaxy at z = 0.0541. They exploded within 200 d from each other at a separation of 0.6arcsec0.6arcsec corresponding to a projected distance of only 0.6 kpc. Performing SALT2 light-curve fits to the gri ZTF photometry, we show that for these equally distant ‘standardizable candles’, there is a difference of 2 mag in their rest-frame B-band peaks, and the fainter supernova (SN) has a significantly red SALT2 colour c = 0.57 ± 0.04, while the stretch values x1 of the two SNe are similar, suggesting that the fainter SN is attenuated by dust in the interstellar medium of the host galaxy. We use these measurements to infer the SALT2 colour standardization parameter, β = 3.5 ± 0.3, independent of the underlying cosmology and Malmquist bias. Assuming the colour excess is entirely due to dust, the result differs by 2σ from the average Milky Way total-to-selective extinction ratio, but is in good agreement with the colour–brightness corrections empirically derived from the most recent SN Ia Hubble–Lemaitre diagram fits. Thus we suggest that SN ‘siblings’, which will increasingly be discovered in the coming years, can be used to probe the validity of the colour and light-curve shape corrections using in SN Ia cosmology while avoiding important systematic effects in their inference from global multiparameter fits to inhomogeneous data sets, and also help constrain the role of interstellar dust in SN Ia cosmology.
|
|
| 2. |
- Fremling, Christoffer, 1984-, et al.
(author)
-
Oxygen and helium in stripped-envelope supernovae
-
Other publication (other academic/artistic)abstract
- We present a spectral analysis of 513 spectra of 176 stripped-envelope (SE) supernovae (SNe) discovered by the untargeted Palomar Transient Factory (PTF) and intermediate PTF (iPTF) surveys. Our sample contains 44 Type Ib SNe, 55 Type IIb SNe, 59 Type Ic SNe and 18 Type Ib/c SNe. We aim to identify differences among the SE SN subtypes in order to put constraints on their progenitors via measurements of the pseudo equivalent widths (pEWs) and velocities of the He I λλ5876,7065, and O I λ7774 lines. We find that Type Ic SNe show higher pEWs and velocities in their O I λ7774 absorption signatures compared to Type IIb and Type Ib SNe. The pEWs of the He I λλ5876,7065 absorption lines are similar in Type Ib and Type IIb SNe, with a few Type Ib SNe showing stronger absorptions prior to maximum light in the He I λ5876 line. The He I λλ5876,7065 velocities at maximum light are higher.We have also identified an anti-correlation between He I λ7065 pEW and O I λ7774 velocity among Type IIb and Type Ib SNe. If both Type Ib and Type Ic SNe had similar amounts of He, and if low mixing was responsible for hiding He in Type Ic SNe, systematically lower velocities and lower oxygen line strengths are predicted for Type Ic SNe. This is contrary to what we have observed. If He is not hidden, it must have been lost in Type Ic SNe. The anti-correlation for Type Ib and Type IIb SNe then suggests that varying amounts of He can be present the time of explosion. The observed difference in the average O I λ7774 velocity around maximum light of Type Ic (~9800 km s-1) and Type Ib SNe (~7900 km s-1) can be explained by the removal of ~0.9 solar masses from the envelope, on average, if the other explosion parameters are assumed to be unchanged between the subtypes.
|
|
| 3. |
- Fremling, Christoffer, 1984-
(author)
-
PTF12os and iPTF13bvn : Two stripped-envelope supernovae discovered by the Palomar Transient Factory
- 2016
-
Licentiate thesis (other academic/artistic)abstract
- This thesis is based on research made by the intermediate Palomar Transient Factory [(i)PTF], and it is particularly closely tied to the still ongoing research on the stripped-envelope (SE) supernova (SN), iPTF13bvn (Type Ib), that occurred in the nearby galaxy NGC 5806. This SN was initially thought to have been the explosion of a very massive Wolf-Rayet (WR) star, but I have shown that this is very likely not the case. I suggest instead that the most likely scenario is that iPTF13bvn originated from a binary system where the envelope was stripped off from the SN progenitor by tidal forces from a companion star, in a similar way as for the very well studied Type IIb SN 2011dh. I have also investigated another SE SN, PTF12os (Type IIb), that occurred in the same galaxy as iPTF13bvn, with the conclusion that PTF12os and iPTF13bvn are very similar amongst themselves, and that both of them are also remarkably similar to SN 2011dh, in terms of all of the available observations (light-curves, spectra). Hydrodynamical models have been used to constrain the explosion parameters of iPTF13bvn, PTF12os and SN 2011dh; finding 56Ni masses in the range 0.063 − 0.075 M⊙, ejecta masses in the range 1.85 − 1.91 M⊙. Using the 56Ni-masses derived from our hydrodynamical modeling in combination with nebular models and late-time spectroscopy we were able to constrain the Zero-Age Main Sequence (ZAMS) mass to ∼ 12 M⊙ for iPTF13bvn and ≲ 15 M⊙ for PTF12os. In current stellar evolution models, stars with these masses on the ZAMS cannot lose their hydrogen envelopes and become SE SNe without binary interactions.
|
|
| 4. |
- Fremling, Christoffer, 1984-
(author)
-
Stripped-envelope supernovae discovered by the Palomar Transient Factory
- 2017
-
Doctoral thesis (other academic/artistic)abstract
- This thesis is based on research made by the intermediate Palomar Transient Factory [(i)PTF]. The focus is on stripped-envelope (SE) supernovae (SNe) discovered by (i)PTF, and it is closely tied to the research on the SE SN iPTF13bvn, that occurred in the nearby galaxy NGC 5806. This SN was initially thought to have been the explosion of a very massive Wolf-Rayet star, but we have shown that this is very likely not the case. We suggest instead that iPTF13bvn originated from a binary system where the envelope was stripped off from the SN progenitor by tidal forces from a companion (Paper I). PTF12os exploded in the same galaxy as iPTF13bvn, and our analysis shows that PTF12os and iPTF13bvn were very similar, and that both were also remarkably similar to the Type IIb SN 2011dh, in terms of their light-curves and spectra. In Paper II, hydrodynamical models were used to constrain the explosion parameters of iPTF13bvn, PTF12os and SN 2011dh; finding 56Ni masses in the range 0.063-0.075 solar masses (Ms), ejecta masses in the range 1.85-1.91 Ms, and kinetic energies in the range 0.54-0.94 x 1051 erg. Furthermore, using nebular models and late-time spectroscopy we were able to constrain the Zero-Age Main Sequence (ZAMS) mass to ~ 12 Ms, for iPTF13bvn and ≤ 15 Ms for PTF12os. In current stellar evolution models, stars with these masses on the ZAMS cannot lose their envelopes and become SE SNe without binary interactions. In Paper III we investigate a peculiar SE SN, iPTF15dtg; this SN lacks both hydrogen and helium and shows a double-peaked LC with a broad main LC peak. Using hydrodynamical modeling we show that iPTF15dtg had a very large ejecta mass (~ 10 Ms), resulting from an explosion of a very massive star (~ 35 Ms). The initial peak in the LC can be explained by the presence of extended material around the star, likely due to an episode of strong mass-loss experienced by the progenitor prior to the explosion. In Paper IV we perform a statistical study of the spectra of all 176 SE SNe (Type IIb, Ib and Ic) discovered by (i)PTF. The spectra of Type Ic SNe show O absorption features that are both stronger and broader (indicating faster expansion velocities) compared to Type IIb and Type Ib SNe. These findings along with very weak He absorption support the traditional picture with Type Ic SNe being heavily stripped of their He envelopes prior to the explosions, and argue against alternative explanations, such as differences in explosive mixing of 56Ni among the SE SN subtypes.
|
|
| 5. |
- Goobar, Ariel, 1962-, et al.
(author)
-
Uncovering a population of gravitational lens galaxies with magnified standard candle SN Zwicky
- 2023
-
In: Nature Astronomy. - 2397-3366. ; 7:9, s. 1098-1107
-
Journal article (peer-reviewed)abstract
- Detecting gravitationally lensed supernovae is among the biggest challenges in astronomy. It involves a combination of two very rare phenomena: catching the transient signal of a stellar explosion in a distant galaxy and observing it through a nearly perfectly aligned foreground galaxy that deflects light towards the observer. Here we describe how high-cadence optical observations with the Zwicky Transient Facility, with its unparalleled large field of view, led to the detection of a multiply imaged type Ia supernova, SN Zwicky, also known as SN 2022qmx. Magnified nearly 25-fold, the system was found thanks to the standard candle nature of type Ia supernovae. High-spatial-resolution imaging with the Keck telescope resolved four images of the supernova with very small angular separation, corresponding to an Einstein radius of only θE = 0.167″ and almost identical arrival times. The small θE and faintness of the lensing galaxy are very unusual, highlighting the importance of supernovae to fully characterize the properties of galaxy-scale gravitational lenses, including the impact of galaxy substructures.
|
|
| 6. |
- Jencson, Jacob E., et al.
(author)
-
The SPIRITS Sample of Luminous Infrared Transients : Uncovering Hidden Supernovae and Dusty Stellar Outbursts in Nearby Galaxies
- 2019
-
In: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 886:1
-
Journal article (peer-reviewed)abstract
- We present a systematic study of the most luminous (M-IR [Vega magnitudes] brighter than ?14) infrared (IR) transients discovered by the SPitzer InfraRed Intensive Transients Survey (SPIRITS) between 2014 and 2018 in nearby galaxies (D < 35 Mpc). The sample consists of nine events that span peak IR luminosities of M-[4.5],M-peak between ?14 and ?18.2, show IR colors between 0.2;<;([3.6]?[4.5]);<;3.0, and fade on timescales between 55 days;t(fade);<;480 days. The two reddest events (A(V) > 12) show multiple, luminous IR outbursts over several years and have directly detected, massive progenitors in archival imaging. With analyses of extensive, multiwavelength follow-up, we suggest the following possible classifications: five obscured core-collapse supernovae (CCSNe), two erupting massive stars, one luminous red nova, and one intermediate-luminosity red transient. We define a control sample of all optically discovered transients recovered in SPIRITS galaxies and satisfying the same selection criteria. The control sample consists of eight CCSNe and one Type;Iax SN. We find that 7 of the 13 CCSNe in the SPIRITS sample have lower bounds on their extinction of 2;A(V);<;8. We estimate a nominal fraction of CCSNe in nearby galaxies that are missed by optical surveys as high as
|
|
| 7. |
- Kool, Erik C., et al.
(author)
-
A radio-detected type Ia supernova with helium-rich circumstellar material
- 2023
-
In: Nature. - 0028-0836 .- 1476-4687. ; 617:7961, s. 477-482
-
Journal article (peer-reviewed)abstract
- Type Ia supernovae (SNe Ia) are thermonuclear explosions of degenerate white dwarf stars destabilized by mass accretion from a companion star1, but the nature of their progenitors remains poorly understood. A way to discriminate between progenitor systems is through radio observations; a non-degenerate companion star is expected to lose material through winds2 or binary interaction3 before explosion, and the supernova ejecta crashing into this nearby circumstellar material should result in radio synchrotron emission. However, despite extensive efforts, no type Ia supernova (SN Ia) has ever been detected at radio wavelengths, which suggests a clean environment and a companion star that is itself a degenerate white dwarf star4,5. Here we report on the study of SN 2020eyj, a SN Ia showing helium-rich circumstellar material, as demonstrated by its spectral features, infrared emission and, for the first time in a SN Ia to our knowledge, a radio counterpart. On the basis of our modelling, we conclude that the circumstellar material probably originates from a single-degenerate binary system in which a white dwarf accretes material from a helium donor star, an often proposed formation channel for SNe Ia (refs. 6,7). We describe how comprehensive radio follow-up of SN 2020eyj-like SNe Ia can improve the constraints on their progenitor systems.
|
|
| 8. |
- Sharma, Yashvi, et al.
(author)
-
A Systematic Study of Ia-CSM Supernovae from the ZTF Bright Transient Survey
- 2023
-
In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 948:1
-
Journal article (peer-reviewed)abstract
- Among the supernovae (SNe) that show strong interaction with a circumstellar medium (CSM), there is a rare subclass of Type Ia supernovae, SNe Ia-CSM, which show strong narrow hydrogen emission lines much like SNe IIn but on top of a diluted Type Ia spectrum. The only previous systematic study of this class identified 16 SNe Ia-CSM, eight historic and eight from the Palomar Transient Factory (PTF). Now using the successor survey to PTF, the Zwicky Transient Facility (ZTF), we have classified 12 additional SNe Ia-CSM through the systematic Bright Transient Survey (BTS). Consistent with previous studies, we find these SNe to have slowly evolving optical light curves with peak absolute magnitudes between -19.1 and -21, spectra having weak H ss and large Balmer ldecrements of similar to 7. Out of the 10 SNe from our sample observed by NEOWISE, nine have 3 sigma detections, with some SNe showing a reduction in the red wing of Ha, indicative of newly formed dust. We do not find our SN Ia-CSM sample to have a significantly different distribution of equivalent widths of He I.5876 than SNe IIn as observed in Silverman et al. The hosts tend to be late-type galaxies with recent star formation. We derive a rate estimate of 29+(27)(21) Gpc(-3) yr(-1) for SNe Ia-CSM, which is similar to 0.02%-0.2% of the SN Ia rate. We also identify six ambiguous SNe IIn/Ia-CSM in the BTS sample and including them gives an upper limit rate of 0.07%-0.8%. This work nearly doubles the sample of well-studied Ia-CSM objects in Silverman et al., increasing the total number to 28.
|
|
| 9. |
- Tinyanont, Samaporn, et al.
(author)
-
Supernova 2020wnt : An Atypical Superluminous Supernova with a Hidden Central Engine
- 2023
-
In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 951:1
-
Journal article (peer-reviewed)abstract
- We present observations of a peculiar hydrogen- and helium-poor stripped-envelope (SE) supernova (SN) 2020wnt, primarily in the optical and near-infrared (near-IR). Its peak absolute bolometric magnitude of −20.9 mag (Lbol, peak = (6.8 ± 0.3) × 1043 erg s−1) and a rise time of 69 days are reminiscent of hydrogen-poor superluminous SNe (SLSNe I), luminous transients potentially powered by spinning-down magnetars. Before the main peak, there is a brief peak lasting <10 days post explosion, likely caused by interaction with circumstellar medium (CSM) ejected ∼years before the SN explosion. The optical spectra near peak lack a hot continuum and O ii absorptions, which are signs of heating from a central engine; they quantitatively resemble those of radioactivity-powered hydrogen/helium-poor Type Ic SESNe. At ∼1 yr after peak, nebular spectra reveal a blue pseudo-continuum and narrow O i recombination lines associated with magnetar heating. Radio observations rule out strong CSM interactions as the dominant energy source at +266 days post peak. Near-IR observations at +200–300 days reveal carbon monoxide and dust formation, which causes a dramatic optical light-curve dip. Pair-instability explosion models predict slow light curve and spectral features incompatible with observations. SN 2020wnt is best explained as a magnetar-powered core-collapse explosion of a 28 M⊙ pre-SN star. The explosion kinetic energy is significantly larger than the magnetar energy at peak, effectively concealing the magnetar-heated inner ejecta until well after peak. SN 2020wnt falls into a continuum between normal SNe Ic and SLSNe I, and demonstrates that optical spectra at peak alone cannot rule out the presence of a central engine.
|
|
