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Register a new userOptical and Infrared Photometry of the Unusual Type Ia Supernova 2000cx
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We present optical and infrared photometry of the unusual Type Ia supernova 2000cx. With the data of Li et al. (2001) and Jha (2002), this comprises the largest dataset ever assembled for a Type Ia SN, more than 600 points in UBVRIJHK. We confirm the finding of Li et al. regarding the unusually blue B-V colors as SN 2000cx entered the nebular phase. Its I-band secondary hump was extremely weak given its B-band decline rate. The V minus near infrared colors likewise do not match loci based on other slowly declining Type Ia SNe, though V-K is the least ``abnormal. In several ways SN 2000cx resembles other slow decliners, given its B-band decline rate (Delta m_15(B) = 0.93), the appearance of Fe III lines and weakness of Si II in its pre-maximum spectrum, the V-K colors and post-maximum V-H colors. If the distance modulus derived from Surface Brightness Fluctuations of the host galaxy is correct, we find that the rate of light increase prior to maximum, the characteristics of the bolometric light curve, and the implied absolute magnitude at maximum are all consistent with a sub-luminous object with Delta m_15(B) ~ 1.6-1.7 having a higher than normal kinetic energy.
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We present optical and near-infrared photometry, along with optical spectra, of the Type Ia supernova SN 2000E in the spiral galaxy NGC 6951. It was discovered by the staff of the Teramo Observatory during the monitoring of the SN 1999el. The observations span a time interval of 234 days in the optical and 134 days in the near-infrared (starting 16 days and 7 days before maximum B light, respectively). Optical spectra are available from 6 days before maximum B light to 122 days after it. SN 2000E exhibits a Dm15(B) = 0.94, thus being classifiable as a slow-declining Type Ia SN and showing the distinctive features of such a class of objects. Spectroscopically, SN 2000E appears as a normal Type Ia SN, like SN 1990N. We could constrain reddening [E(B-V) ~0.5 mag] and distance (mu0 ~32.14 mag) using a number of different methods. The bolometric luminosity curve of SN 2000E, allows a determination of the Ni56 mass amounting to 0.9Msun.
We have conducted a systematic and comprehensive monitoring programme of the Type Ia supernova 2000cx at late phases using the VLT and HST. The VLT observations cover phases 360 to 480 days past maximum brightness and include photometry in the BVRIJH bands, together with a single epoch in each of U and Ks. While the optical bands decay by about 1.4 mag per 100 days, we find that the near-IR magnitudes stay virtually constant during the observed period. This means that the importance of the near-IR to the bolometric light curve increases with time. The finding is also in agreement with our detailed modeling of a Type Ia supernova in the nebular phase. In these models, the increased importance of the near-IR is a temperature effect. We note that this complicates late-time studies where often only the V band is well monitored. In particular, it is not correct to assume that any optical band follows the bolometric light curve at these phases, and any conclusions based on such assumptions, e.g., regarding positron-escape, must be regarded as premature. A very simple model where all positrons are trapped can reasonably well account for the observations. The nickel mass deduced from the positron tail of this light curve is lower than found from the peak brightness, providing an estimate of the fraction of late-time emission that is outside of the observed wavelength range. Our detailed models show the signature of an infrared catastrophe at these epochs, which is not supported by the observations.
The Type Ia SN 2000cx exhibited multiple peculiarities, including a lopsided B-band light-curve peak that does not conform to current methods for using shapes of light curves to standardize SN Ia luminosities. We use the parameterized supernova synthetic-spectrum code SYNOW to study line identifications in the photospheric-phase spectra of SN 2000cx. Previous work established the presence of Ca II infrared-triplet features forming above velocity about 20,000 km/s, much higher than the photospheric velocity of about 10,000 km/s. We find Ti II features forming at the same high velocity. High-velocity line formation is partly responsible for the photometric peculiarities of SN 2000cx: for example, B-band flux blocking by Ti II absorption features that decreases with time causes the B light curve to rise more rapidly and decline more slowly than it otherwise would. SN 2000cx contains an absorption feature near 4530 A that may be H-beta, forming at the same high velocity. The lack of conspicuous H-alpha and P-alpha signatures does not necessarily invalidate the H-beta identification if the high-velocity line formation is confined to a clump that partly covers the photosphere and the H-alpha and P-alpha source functions are elevated relative to that of resonance scattering. The H-beta identification is tentative. If it is correct, the high-velocity matter must have come from a nondegenerate companion star.
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 39 nights of optical photometry, 34 nights of infrared photometry, and 4 nights of optical spectroscopy of the Type Ia SN 1999ac. This supernova was discovered two weeks before maximum light, and observations were begun shortly thereafter. At early times its spectra resembled the unusual SN 1999aa and were characterized by very high velocities in the Ca II H and K lines, but very low velocities in the Si II 6355 A line. The optical photometry showed a slow rise to peak brightness but, quite peculiarly, was followed by a more rapid decline from maximum. Thus, the B- and V-band light curves cannot be characterized by a single stretch factor. We argue that the best measure of the nature of this object is not the decline rate parameter Delta m_15 (B). The B-V colors were unusual from 30 to 90 days after maximum light in that they evolved to bluer values at a much slower rate than normal Type Ia supernovae. The spectra and bolometric light curve indicate that this event was similar to the spectroscopically peculiar slow decliner SN 1999aa.
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