Supernova 1998S

[SN 1998S NIR Spectrum at t=95 d]Near-Infrared Spectrum of SN 1998S 95 days after Vmax.

At day 95, the Near-Infrared spectrum of SN 1998S exhibited broad emission from hydrogen and helium recombination lines as well as some low-ionization line emission from O,Mg, Si and Fe. Also visable in this spectrum is the "second overtone" feature of Carbon Monoxide (CO). This is the third supernova in which molecular emission has been detected.

[SN 1998S Optical Spectrum at t=225 d]Optical Spectrum of SN 1998S 225 days after Vmax.



[SN 1998S NIR spectrum at t=225 d]Near-Infrared Spectrum of SN 1998S 225 days after Vmax.



[Dust emission in SN 1998S and SN 1997ab]Near-Infrared spectra of SN 1998S at t=355 d and SN 1997ab at t = 1064+ d.

Both of these spectra exhibit a red continuum which is well fit by a single 1200 K blackbody curve. Note that the relative flux level across the 1.8 - 2.0 micron gap is uncertain by up to 30%. The top spectrum in each panel shows the fit to the data as reduced. In the lower plot of each panel the flux of the K-band region has been adjusted as a free parameter during the fitting proceedure. Both SN 1998S and SN 1997ab are Type IIn supernovae, and the NIR continuum in these objects is likely thermal emission from dust heated by a strong interaction with a dense circumstellar medium.

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