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Published October 20, 2009 | Published
Journal Article Open

Multi-Wavelength Properties of the Type IIb SN 2008ax


We present the UV, optical, X-ray, and radio properties of the Type IIb SN 2008ax discovered in NGC 4490. The observations in the UV are one of the earliest of a Type IIb supernova (SN). On approximately day 4 after the explosion, a dramatic upturn in the u and uvw1 (λ_c = 2600 Å) light curves occurred after an initial rapid decline which is attributed to adiabatic cooling after the initial shock breakout. This rapid decline and upturn is reminiscent of the Type IIb SN 1993J on day 6 after the explosion. Optical/near-IR spectra taken around the peak reveal prominent Hα, He I, and Ca II absorption lines. A fading X-ray source is also located at the position of SN 2008ax, implying an interaction of the SN shock with the surrounding circumstellar material and a mass-loss rate of the progenitor of M (overdot) = (9 ± 3) × 10^(−6) M_☉ yr^(−1). The unusual time evolution (14 days) of the 6 cm peak radio luminosity provides further evidence that the mass-loss rate is low. Combining the UV, optical, X-ray, and radio data with models of helium exploding stars implies the progenitor of SN 2008ax was an unmixed star in an interacting binary. Modeling of the SN light curve suggests a kinetic energy (E_k) of 0.5 × 10^(51) erg, an ejecta mass (M_(ej)) of 2.9 M_☉, and a nickel mass (M_(Ni)) of 0.06 M_☉.

Additional Information

© 2009 American Astronomical Society. Received 2009 August 31; accepted 2009 September 17; published 2009 October 5. We thank Alicia Soderberg for suggestions regarding this work, which is sponsored at PSU by NASA contract NAS5-00136 and at Marquette by NASA award NNX09AC90G. The HET of UT-Austin, PSU, Stanford, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen, is named in honor of William Hobby and Robert Eberly.

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Published - Roming2009p6243Astrophys_J_Lett.pdf


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August 21, 2023
October 19, 2023