The Distance to SN 1999em in NGC 1637 from the Expanding Photosphere Method

• Published in: Publications of the Astronomical Society of the Pacific 2002-01, Vol.114 (791), p.35-64
• Main Authors: Leonard, Douglas C., Filippenko, Alexei V., Gates, Elinor L., Li, Weidong, Eastman, Ronald G., Barth, Aaron J., Bus, Schelte J., Chornock, Ryan, Coil, Alison L., Frink, Sabine, Grady, Carol A., Harris, Alan W., Malkan, Matthew A., Matheson, Thomas, Quirrenbach, Andreas, Treffers, Richard R.
• Format: Article
• Language: English
• Subjects: Absorption spectra; Asphericity; Cepheids; Galaxies; Hydrogen; Line spectra; Photometry; Photospheres; Visible spectrum; Wavelengths
• ISSN: 0004-6280; 1538-3873
• DOI: 10.1086/324785

We present 30 optical spectra and 49 photometric epochs sampling the first 517 days after discovery of supernova (SN) 1999em and derive its distance through the expanding photosphere method (EPM). SN 1999em is shown to be a Type II‐plateau (II‐P) event, with a photometric plateau lasting until about 100 days after explosion. We identify the dominant ions responsible for most of the absorption features seen in the optical portion of the spectrum during the plateau phase. Using the weakest unblended absorption features to estimate photospheric velocity, we find the distance to SN 1999em to be \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $D=8.2\pm 0.6$ \end{document} Mpc, with an explosion date of HJD \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $2,451,475.6\pm 1.4$ \end{document} , or \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $5.3\pm 1.4$ \end{document} days before discovery. We show that this distance estimate is about 10% closer than the distance that results if the strong Feiiλλ4924, 5018, 5169 absorption features, w