| 1. |
- Boldt, Luis N., et al.
(författare)
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Near-Infrared K Corrections of Type Ia Supernovae and their Errors
- 2014
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 126:938, s. 324-337
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we use near-infrared (NIR) spectral observations of Type Ia supernovae (SNe Ia) to study the uncertainties inherent in NIR K corrections. To do so, 75 previously published NIR spectra of 33 SNe Ia are employed to determine K-correction uncertainties in the YJHK(s) passbands as a function of temporal phase and redshift. The resultant K corrections are then fed into an interpolation algorithm that provides mean K corrections as a function of temporal phase and robust estimates of the associated errors. These uncertainties are both statistical and intrinsic-i.e., due to the diversity of spectral features from object to object and must be included in the overall error budget of cosmological parameters constrained through the use of NIR observations of SNe Ia. Intrinsic variations are likely the dominant source of error for all four passbands at maximum light. Given the present data, the total Y-band K-correction uncertainties at maximum are smallest, amounting to +/- 0.04 mag at a redshift of z = 0.08. The J-band K-term errors are also reasonably small (+/- 0.06 mag), but intrinsic variations of spectral features and noise introduced by telluric corrections in the H-band currently limit its total K-correction errors at maximum to +/- 0.10 mag at z = 0.08. Finally, uncertainties in the K-s-band K terms at maximum amount to +/- 0.07 mag at this same redshift. These results are largely constrained by the small number of published NIR spectra of SNe Ia, which do not yet allow spectral templates to be constructed as a function of the light curve decline rate.
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| 2. |
- Burns, Christopher R., et al.
(författare)
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THE CARNEGIE SUPERNOVA PROJECT : LIGHT-CURVE FITTING WITH SNooPy
- 2011
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 141:1, s. 19-
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Tidskriftsartikel (refereegranskat)abstract
- In providing an independent measure of the expansion history of the universe, the Carnegie Supernova Project (CSP) has observed 71 high-z Type Ia supernovae (SNe Ia) in the near-infrared bands Y and J. These can be used to construct rest-frame i-band light curves which, when compared to a low-z sample, yield distance moduli that are less sensitive to extinction and/or decline-rate corrections than in the optical. However, working with NIR observed and i-band rest-frame photometry presents unique challenges and has necessitated the development of a new set of observational tools in order to reduce and analyze both the low-z and high-z CSP sample. We present in this paper the methods used to generate uBVgriYJH light-curve templates based on a sample of 24 high-quality low-z CSP SNe. We also present two methods for determining the distances to the hosts of SN Ia events. A larger sample of 30 low-z SNe Ia in the Hubble flow is used to calibrate these methods. We then apply the method and derive distances to seven galaxies that are so nearby that their motions are not dominated by the Hubble flow.
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| 3. |
- Clark, Peter, et al.
(författare)
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LSQ13ddu : a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 492:2, s. 2208-2228
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 +/- 0.9 d to reach a peak brightness of -19.70 +/- 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow He I features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow He I velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive Ni-56 powering but can be explained through a combination of CSM interaction and an underlying Ni-56 decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib.
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| 4. |
- D'Andrea, Chris B., et al.
(författare)
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Type II-P Supernovae from the SDSS-II Supernova Survey and the Standardized Candle Method
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 708:1, s. 661-674
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Tidskriftsartikel (refereegranskat)abstract
- We apply the Standardized Candle Method (SCM) for Type II Plateau supernovae (SNe II-P), which relates the velocity of the ejecta of a SN to its luminosity during the plateau, to 15 SNe II-P discovered over the three season run of the Sloan Digital Sky Survey-II Supernova Survey. The redshifts of these SNe—0.027 < z < 0.144—cover a range hitherto sparsely sampled in the literature; in particular, our SNe II-P sample contains nearly as many SNe in the Hubble flow (z > 0.01) as all of the current literature on the SCM combined. We find that the SDSS SNe have a very small intrinsic I-band dispersion (0.22 mag), which can be attributed to selection effects. When the SCM is applied to the combined SDSS-plus-literature set of SNe II-P, the dispersion increases to 0.29 mag, larger than the scatter for either set of SNe separately. We show that the standardization cannot be further improved by eliminating SNe with positive plateau decline rates, as proposed in Poznanski et al. We thoroughly examine all potential systematic effects and conclude that for the SCM to be useful for cosmology, the methods currently used to determine the Fe II velocity at day 50 must be improved, and spectral templates able to encompass the intrinsic variations of Type II-P SNe will be needed. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.
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| 5. |
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| 6. |
- Ergon, Mattias, 1967-, et al.
(författare)
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Light curve and spectral modelling of the type IIb SN 2020acat. Evidence for a strong Ni bubble effect on the diffusion time
- 2024
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 683
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Tidskriftsartikel (refereegranskat)abstract
- We use the light-curve and spectral synthesis code JEKYLL to calculate a set of macroscopically mixed type IIb supernova (SN) models, which are compared to both previously published and new late-phase observations of SN 2020acat. The models differ in the initial mass, in the radial mixing and expansion of the radioactive material, and in the properties of the hydrogen envelope. The best match to the photospheric and nebular spectra and light curves of SN 2020acat is found for a model with an initial mass of 17 M⊙, strong radial mixing and expansion of the radioactive material, and a 0.1 M⊙ hydrogen envelope with a low hydrogen mass fraction of 0.27. The most interesting result is that strong expansion of the clumps containing radioactive material seems to be required to fit the observations of SN 2020acat both in the diffusion phase and in the nebular phase. These Ni bubbles are expected to expand due to heating from radioactive decays, but the degree of expansion is poorly constrained. Without strong expansion, there is a tension between the diffusion phase and the subsequent evolution, and models that fit the nebular phase produce a diffusion peak that is too broad. The diffusion-phase light curve is sensitive to the expansion of the Ni bubbles because the resulting Swiss-cheese-like geometry decreases the effective opacity and therefore the diffusion time. This effect has not been taken into account in previous light-curve modelling of stripped-envelope SNe, which may lead to a systematic underestimate of their ejecta masses. In addition to strong expansion, strong mixing of the radioactive material also seems to be required to fit the diffusion peak. It should be emphasized, however, that JEKYLL is limited to a geometry that is spherically symmetric on average, and large-scale asymmetries may also play a role. The relatively high initial mass found for the progenitor of SN 2020acat places it at the upper end of the mass distribution of type IIb SN progenitors, and a single-star origin cannot be excluded.
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| 7. |
- Folatelli, Gaston, et al.
(författare)
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UNBURNED MATERIAL IN THE EJECTA OF TYPE Ia SUPERNOVAE
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 745:1, s. 74-
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Tidskriftsartikel (refereegranskat)abstract
- The presence of unburned material in the ejecta of normal Type Ia supernovae (SNe Ia) is investigated using early-time spectroscopy obtained by the Carnegie Supernova Project. The tell-tale signature of pristine material from a C+O white dwarf progenitor star is the presence of carbon, as oxygen is also a product of carbon burning. The most prominent carbon lines in optical spectra of SNe Ia are expected to arise from C II. We find that at least 30% of the objects in the sample show an absorption at approximate to 6300 angstrom which is attributed to C II lambda 6580. An alternative identification of this absorption as Ha is considered to be unlikely. These findings imply a larger incidence of carbon in SNe Ia ejecta than previously noted. We show how observational biases and physical conditions may hide the presence of weak C II lines, and account for the scarcity of previous carbon detections in the literature. This relatively large frequency of carbon detections has crucial implications on our understanding of the explosive process. Furthermore, the identification of the 6300 angstrom absorptions as carbon would imply that unburned material is present at very low expansion velocities, merely approximate to 1000 km s(-1) above the bulk of Si II. Based on spectral modeling, it is found that the detections are consistent with a mass of carbon of 10(-3) to 10(-2) M-circle dot. The presence of this material so deep in the ejecta would imply substantial mixing, which may be related to asymmetries of the flame propagation. Another possible explanation for the carbon absorptions may be the existence of clumps of unburned material along the line of sight. However, the uniformity of the relation between C II and Si II velocities is not consistent with such small-scale asymmetries. The spectroscopic and photometric properties of SNe Ia with and without carbon signatures are compared. A trend toward bluer color and lower luminosity at maximum light is found for objects which show carbon.
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| 8. |
- Foley, Ryan J., et al.
(författare)
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ON THE PROGENITOR AND SUPERNOVA OF THE SN 2002cx-LIKE SUPERNOVA 2008ge
- 2010
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 140:5, s. 1321-1328
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Tidskriftsartikel (refereegranskat)abstract
- We present observations of supernova (SN) 2008ge, which is spectroscopically similar to the peculiar SN 2002cx, and its pre-explosion site indicating that its progenitor was probably a white dwarf. NGC 1527, the host galaxy of SN 2008ge, is an S0 galaxy with no evidence of star formation or massive stars. Astrometrically matching late-time imaging of SN 2008ge to pre-explosion Hubble Space Telescope imaging, we constrain the luminosity of the progenitor star. Since SN 2008ge has no indication of hydrogen or helium in its spectrum, its progenitor must have lost its outer layers before exploding, meaning that it is a white dwarf, a Wolf-Rayet star, or a lower-mass star in a binary system. Observations of the host galaxy show no signs of individual massive stars, star clusters, or H (II) regions at the SN position or anywhere else, making a Wolf-Rayet progenitor unlikely. Late-time spectroscopy of SN 2008ge shows strong [Fe (II)] lines with large velocity widths compared to other members of this class at similar epochs. These previously unseen features indicate that a significant amount of the SN ejecta is Fe (presumably the result of the radioactive decay of Ni-56 generated in the SN), further supporting a thermonuclear explosion. Placing the observations of SN 2008ge in the context of observations of other objects in the same class of SNe, we suggest that the progenitor was most likely a white dwarf.
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| 9. |
- Foley, Ryan J., et al.
(författare)
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THE FIRST MAXIMUM-LIGHT ULTRAVIOLET THROUGH NEAR-INFRARED SPECTRUM OF A TYPE Ia SUPERNOVA
- 2012
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Ingår i: THE ASTROPHYSICAL JOURNAL LETTERS. - 2041-8205. ; 753:1, s. L5-
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Tidskriftsartikel (refereegranskat)abstract
- We present the first maximum-light ultraviolet (UV) through near-infrared (NIR) Type Ia supernova (SN Ia) spectrum. This spectrum of SN 2011iv was obtained nearly simultaneously by the Hubble Space Telescope at UV/optical wavelengths and the Magellan Baade telescope at NIR wavelengths. These data provide the opportunity to examine the entire maximum-light SN Ia spectral energy distribution. Since the UV region of an SN Ia spectrum is extremely sensitive to the composition of the outer layers of the explosion, which are transparent at longer wavelengths, this unprecedented spectrum can provide strong constraints on the composition of the SN ejecta, and similarly the SN explosion and progenitor system. SN 2011iv is spectroscopically normal, but has a relatively fast decline (Delta m(15)(B) = 1.69 +/- 0.05 mag). We compare SN 2011iv to other SNe Ia with UV spectra near maximum light and examine trends between UV spectral properties, light-curve shape, and ejecta velocity. We tentatively find that SNe with similar light-curve shapes but different ejecta velocities have similar UV spectra, while those with similar ejecta velocities but different light-curve shapes have very different UV spectra. Through a comparison with explosion models, we find that both a solar-metallicity W7 and a zero-metallicity delayed-detonation model provide a reasonable fit to the spectrum of SN 2011iv from the UV to the NIR.
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| 10. |
- Fox, Ori D., et al.
(författare)
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The slow demise of the long-lived SN 2005ip
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 498:1, s. 517-531
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Tidskriftsartikel (refereegranskat)abstract
- The Type IIn supernova (SN IIn) 2005ip is one of the most well-studied and long-lasting examples of an SN interacting with its circumstellar environment. The optical light curve plateaued at a nearly constant level for more than five years, suggesting ongoing shock interaction with an extended and clumpy circumstellar medium (CSM). Here, we present continued observations of the SN from ∼1000 to 5000 d post-explosion at all wavelengths, including X-ray, ultraviolet, near-infrared (NIR), and mid-infrared. The UV spectra probe the pre-explosion mass loss and show evidence for CNO processing. From the bolometric light curve, we find that the total radiated energy is in excess of 1050 erg, the progenitor star’s pre-explosion mass-loss rate was ≳1×10−2M⊙ yr−1, and the total mass lost shortly before explosion was ≳1M⊙, though the mass lost could have been considerably larger depending on the efficiency for the conversion of kinetic energy to radiation. The ultraviolet through NIR spectrum is characterized by two high-density components, one with narrow high-ionization lines, and one with broader low-ionization H i, He i, [O i], Mg ii, and Fe ii lines. The rich Fe ii spectrum is strongly affected by Lyα fluorescence, consistent with spectral modelling. Both the Balmer and He i lines indicate a decreasing CSM density during the late interaction period. We find similarities to SN 1988Z, which shows a comparable change in spectrum at around the same time during its very slow decline. These results suggest that, at long last, the shock interaction in SN 2005ip may finally be on the decline.
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