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Register a new userOptical and Infrared photometry of the type IIn SN 1998S:Days 11-146
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We present contemporaneous optical and infrared photometric observations of the type IIn SN 1998S covering the period between 11 and 146 days after discovery. The infrared data constitute the first ever infrared light curves of a type IIn supernova. We use blackbody and spline fits to the photometry to examine the luminosity evolution. During the first 2--3 months, the luminosity is dominated by the release of shock-deposited energy in the ejecta. After $sim$100 days the luminosity is powered mostly by the deposition of radioactive decay energy from 0.15$pm$0.05 M$_{odot}$ of $^{56}$Ni which was produced in the explosion. We also report the discovery of an astonishingly high infrared (IR) excess, $K-L=2.5$, that was present at day 130. We interpret this as being due to thermal emission from dust grains in the vicinity of the supernova. We argue that to produce such a high IR luminosity so soon after the explosion, the dust must be {it pre-existing} and so is located in the circumstellar medium of the progenitor. The dust could be heated either by the UV/optical flash (IR echo) or by the X-rays from the interaction of the ejecta with the circumstellar material
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Near-infrared photometric observations of the Type IIn SN 2005ip in NGC 2906 reveal large fluxes (>1.3 mJy) in the K_s-band over more than 900 days. While warm dust can explain the late-time K_s-band emission of SN 2005ip, the nature of the dust heating source is ambiguous. Shock heating of pre-existing dust by post-shocked gas is unlikely because the forward shock is moving too slowly to have traversed the expected dust-free cavity by the time observations first reveal the K_s emission. While an infrared light echo model correctly predicts a near-infrared luminosity plateau, heating dust to the observed temperatures of ~1400-1600 K at a relatively large distance from the supernova (> 10^{18} cm) requires an extraordinarily high early supernova luminosity (~1 X 10^{11} L_solar). The evidence instead favors condensing dust in the cool, dense shell between the forward and reverse shocks. Both the initial dust temperature and the evolutionary trend towards lower temperatures are consistent with this scenario. We infer that radiation from the circumstellar interaction heats the dust. While this paper includes no spectroscopic confirmation, the photometry is comparable to other SNe that do show spectroscopic evidence for dust formation. Observations of dust formation in SNe are sparse, so these results provide a rare opportunity to consider SNe Type IIn as dust sources.
We present contemporary infrared and optical spectroscopic observations of the type IIn SN 1998S for the period between 3 and 127 days after discovery. In the first week the spectra are characterised by prominent broad emission lines with narrow peaks superimposed on a very blue continuum(T~24000K). In the following two weeks broad, blueshifted absorption components appeared in the spectra and the temperature dropped. By day 44, broad emission components in H and He reappeared in the spectra. These persisted to 100-130d, becoming increasingly asymmetric. We agree with Leonard et al. (2000) that the broad emission lines indicate interaction between the ejecta and circumstellar material (CSM) and deduce that progenitor of SN 1998S appears to have gone through at least two phases of mass loss, giving rise to two CSM zones. Examination of the spectra indicates that the inner zone extended to <90AU, while the outer CSM extended from 185AU to over 1800AU. Analysis of high resolution spectra shows that the outer CSM had a velocity of 40-50 km/s. Assuming a constant velocity, we can infer that the outer CSM wind commenced more than 170 years ago, and ceased about 20 years ago, while the inner CSM wind may have commenced less than 9 years ago. During the era of the outer CSM wind the outflow was high, >2x10^{-5}M_{odot}/yr corresponding to a mass loss of at least 0.003M_{odot} and suggesting a massive progenitor. We also model the CO emission observed in SN 1998S. We deduce a CO mass of ~10^{-3} M_{odot} moving at ~2200km/s, and infer a mixed metal/He core of ~4M_{odot}, again indicating a massive progenitor.
On 2017 March 11, the DLT40 Transient Discovery Survey discovered SN 2017cbv in NGC5643, a Type 2 Seyfert Galaxy in the Lupus Constellation. SN 2017cbv went on to become a bright Type Ia supernova, with a $V_{max}$ of 11.51 $pm$ 0.05 mag. We present early time optical and infrared photometry of SN 2017cbv covering the rise and fall of over 68 days. We find that SN 2017cbv has a broad light curve $Delta m_{15}(B)$ = 0.88 $pm$ 0.07, a $B$-band maximum at 2457840.97 $pm$ 0.43, a negligible host galaxy reddening where $E(B-V)_{host}$ $approx$ 0, and a distance modulus of 30.49 $pm$ 0.32 to the SN, corresponding to a distance of $12.58_{-1.71}^{+1.98}$ Mpc. We also present the results of two different numerical models we used for analysis in this paper: SALT2, an empirical model for Type Ia supernova optical light curves that accounts for variability components; and SNooPy, the CSP-II light-curve model that covers both optical and near-infrared wavelengths and is used for distance estimates.
We present an extensive ($sim$ 1200 d) photometric and spectroscopic monitoring of the Type IIn supernova (SN) 2012ab. After a rapid initial rise leading to a bright maximum (M$_{R}$ = $-$19.39 mag), the light curves show a plateau lasting about 2 months followed by a steep decline up to about 100 d. Only in the $U$ band the decline is constant in the same interval. At later phases, the light curves remain flatter than the $^{56}$Co decline suggesting the increasing contribution of the interaction between SN ejecta with circumstellar material (CSM). Although heavily contaminated by emission lines of the host galaxy, the early spectral sequence (until 32 d) shows persistent narrow emissions, indicative of slow unshocked CSM, and the emergence of broad Balmer lines of hydrogen with P-Cygni profiles over a blue continuum, arising from a fast expanding SN ejecta. From about 2 months to $sim$1200 d, the P-Cygni profiles are overcome by intermediate width emissions (FWHM $sim 6000$ kms), produced in the shocked region due to interaction. On the red wing a red bump appears after 76 d, likely a signature of the onset of interaction of the receding ejecta with the CSM. The presence of fast material both approaching and then receding is suggestive that we are observing the SN along the axis of a jet-like ejection in a cavity devoid of or uninterrupted by CSM in the innermost regions.
We present the photometric and spectroscopic evolution of the type IIn SN 1995G in NGC 1643, on the basis of 4 years of optical and infrared observations. This supernova shows very flat optical light curves similar to SN 1988Z, with a slow decline rate at all times. The spectra are characterized by strong Balmer lines with multiple components in emission and with a P-Cygni absorption component blueshifted by only 700 km/s. This feature indicates the presence of a slowly expanding shell above the SN ejecta as in the case of SNe 1994aj and 1996L. As in other SNe IIn the slow luminosity decline cannot be explained only with a radioactive energy input and an additional source of energy is required, most likely that produced by the interaction between supernova ejecta and a pre--existent circumstellar medium. It was estimated that the shell material has a density n(H) >> 10^8 cm^-3, consistent with the absence of forbidden lines in the spectra. About 2 years after the burst the low velocity shell is largely overtaken by the SN ejecta and the luminosity drops at a faster rate.
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