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Register a new userRed and Reddened: Ultraviolet through Near-Infrared Observations of Type Ia Supernova 2017erp
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We present space-based ultraviolet/optical photometry and spectroscopy with the Swift Ultra-Violet/Optical Telescope and Hubble Space Telescope, respectively, along with ground-based optical photometry and spectroscopy and near-infrared spectroscopy of supernova SN2017erp. The optical light curves and spectra are consistent with a normal Type Ia supernova (SN Ia). Compared to previous photometric samples in the near-ultraviolet (NUV), SN2017erp has colors similar to the NUV-red category after correcting for Milky Way and host dust reddening. We find the difference between SN2017erp and the NUV-blue SN2011fe is not consistent with dust reddening alone but is similar to the SALT color law, derived from rest-frame UV photometry of higher redshift SNe Ia. This chromatic difference is dominated by the intrinsic differences in the UV and only a small contribution from the expected dust reddening. Differentiating the two can have important consequences for determining cosmological distances with rest-frame UV photometry. This spectroscopic series is important for analyzing SNe Ia with intrinsically redder NUV colors. We also 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 Angstroms implying a factor of ten higher metallicity in the upper layers of SN2017erp 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.
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Understanding the intrinsic colors of Type Ia supernovae (SNe Ia) is important to their use as cosmological standard candles. Understanding the effects of reddening and redshift on the observed colors are complicated and dependent on the intrinsic spectrum, the filter curves, and the wavelength dependence of reddening. We present ultraviolet and optical data of a growing sample of SNe Ia observed with the Ultra-Violet/Optical Telescope on the Swift spacecraft and use this sample to re-examine the near-UV (NUV) colors of SNe Ia. We find that a small amount of reddening (E(B-V)=0.2 mag) could account for the difference between groups designated as NUV-blue and NUV-red, and a moderate amount of reddening (E(B-V)=0.5 mag) could account for the whole NUV-optical differences. The reddening scenario, however, is inconsistent with the mid-UV colors and color evolution. The effect of redshift alone only accounts for part of the variation. Using a spectral template of SN2011fe we can forward model the effects of redshift and reddening and directly compare with the observed colors. We find that some SNe are consistent with reddene
Supernova (SN) 2017cbv in NGC 5643 is one of a handful of type Ia supernovae (SNe~Ia) reported to have excess blue emission at early times. This paper presents extensive $BVRIYJHK_s$-band light curves of SN 2017cbv, covering the phase from $-16$ to $+125$ days relative to $B$-band maximum light. SN 2017cbv reached a $B$-band maximum of 11.710$pm$0.006~mag, with a post-maximum magnitude decline $Delta m_{15}(B)$=0.990$pm$0.013 mag. The supernova suffered no host reddening based on Phillips intrinsic color, Lira-Phillips relation, and the CMAGIC diagram. By employing the CMAGIC distance modulus $mu=30.58pm0.05$~mag and assuming $H_0$=72~$rm km s^{-1} Mpc^{-1}$, we found that 0.73~msun $^{56}$Ni was synthesized during the explosion of SN 2017cbv, which is consistent with estimates using reddening-free and distance-free methods via the phases of the secondary maximum of the NIR-band light curves. We also present 14 near-infrared spectra from $-18$ to $+49$~days relative to the $B$-band maximum light, providing constraints on the amount of swept-up hydrogen from the companion star in the context of the single degenerate progenitor scenario. No $Pa{beta}$ emission feature was detected from our post-maximum NIR spectra, placing a hydrogen mass upper limit of 0.1 $M_{odot}$. The overall optical/NIR photometric and NIR spectral evolution of SN 2017cbv is similar to that of a normal SN~Ia, even though its early evolution is marked by a flux excess no seen in most other well-observed normal SNe~Ia. We also compare the exquisite light curves of SN 2017cbv with some $M_{ch}$ DDT models and sub-$M_{ch}$ double detonation models.
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 a 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.
We present extensive optical (UBVRI), near-infrared (JK) light curves and optical spectroscopy of the Type Ia supernova (SN) 2006X in the nearby galaxy NGC 4321 (M100). Our observations suggest that either SN 2006X has an intrinsically peculiar color evolution, or it is highly reddened [E(B - V)_{host} = 1.42+/-0.04 mag] with R_V = 1.48+/-0.06, much lower than the canonical value of 3.1 for the average Galactic dust. SN 2006X also has one of the highest expansion velocities ever published for a SN Ia. Compared with the other SNe Ia we analyzed, SN 2006X has a broader light curve in the U band, a more prominent bump/shoulder feature in the V and R bands, a more pronounced secondary maximum in the I and near-infrared bands, and a remarkably smaller late-time decline rate in the B band. The B - V color evolution shows an obvious deviation from the Lira-Phillips relation at 1 to 3 months after maximum brightness. At early times, optical spectra of SN 2006X displayed strong, high-velocity features of both intermediate-mass elements (Si, Ca, and S) and iron-peak elements, while at late times they showed a relatively blue continuum, consistent with the blue U-B and B-V colors at similar epochs. A light echo and/or the interaction of the SN ejecta and its circumstellar material may provide a plausible explanation for its late-time photometric and spectroscopic behavior. Using the Cepheid distance of M100, we derive a Hubble constant of 72.7+/-8.2 km s^{-1} Mpc^{-1}(statistical) from the normalized dereddened luminosity of SN 2006X. We briefly discuss whether abnormal dust is a universal signature for all SNe Ia, and whether the most rapidly expanding objects form a subclass with distinct photometric and spectroscopic properties.
We main goal of this paper is to test whether the NIR peak magnitudes of SNe Ia could be accurately estimated with only a single observation obtained close to maximum light, provided the time of B band maximum and the optical stretch parameter are known. We obtained multi-epoch UBVRI and single-epoch J and H photometric observations of 16 SNe Ia in the redshift range z=0.037-0.183, doubling the leverage of the current SN Ia NIR Hubble diagram and the number of SNe beyond redshift 0.04. This sample was analyzed together with 102 NIR and 458 optical light curves (LCs) of normal SNe Ia from the literature. The analysis of 45 well-sampled NIR LCs shows that a single template accurately describes them if its time axis is stretched with the optical stretch parameter. This allows us to estimate the NIR peak magnitudes even with one observation obtained within 10 days from B-band maximum. We find that the NIR Hubble residuals show weak correlation with DM_15 and E(B-V), and for the first time we report a possible dependence on the J_max-H_max color. The intrinsic NIR luminosity scatter of SNe Ia is estimated to be around 0.10 mag, which is smaller than what can be derived for a similarly heterogeneous sample at optical wavelengths. In conclusion, we find that SNe Ia are at least as good standard candles in the NIR as in the optical. We showed that it is feasible to extended the NIR SN Ia Hubble diagram to z=0.2 with very modest sampling of the NIR LCs, if complemented by well-sampled optical LCs. Our results suggest that the most efficient way to extend the NIR Hubble diagram to high redshift would be to obtain a single observation close to the NIR maximum. (abridged)
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