Preliminary spectral analysis of the type II supernova 1999em

E. Baron, David Branch, Peter H. Hauschildt, Alexei V. Filippenko, R. P. Kirshner, P. M. Challis, Saurabh Jha, R. Chevalier, Claes Fransson, Peter Lundqvist, Peter Garnavich, Bruno Leibundgut, R. Mccray, E. Michael, Nino Panagia, M. M. Phillips, C. S.J. Pun, Brian Schmidt, George Sonneborn, N. B. SuntzeffL. Wang, J. C. Wheeler

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Abstract

We have calculated fast direct spectral model fits to two early-time spectra of the Type II plateau SN 1999em, using the SYNOW synthetic spectrum code. The first is an extremely early blue optical spectrum and the second a combined Hubble Space Telescope and optical spectrum obtained one week later. Spectroscopically this supernova appears to be a normal Type II, and these fits are in excellent agreement with the observed spectra. Our direct analysis suggests the presence of enhanced nitrogen. We have further studied these spectra with the full non-LTE general model atmosphere code PHOENIX. While we do not find confirmation for enhanced nitrogen (nor do we rule it out), we do require enhanced helium. An even more intriguing possible line identification is complicated Balmer and He I lines, which we show falls naturally out of the detailed calculations with a shallow density gradient. We also show that very early spectra such as those presented here combined with sophisticated spectral modeling allow an independent estimate of the total reddening to the supernova, since when the spectrum is very blue, dereddening leads to changes in the blue flux that cannot be reproduced by altering the "temperature" of the emitted radiation. These results are extremely encouraging since they imply that detailed modeling of early spectra can shed light on both the abundances and total extinction of SNe II, the latter improving their utility and reliability as distance indicators.

Original languageEnglish (US)
Pages (from-to)444-448
Number of pages5
JournalAstrophysical Journal
Volume545
Issue number1 PART 1
StatePublished - Dec 10 2000

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spectral analysis
spectrum analysis
supernovae
optical spectrum
nitrogen
Hubble Space Telescope
plateaus
helium
extinction
modeling
atmospheres
plateau
gradients
radiation
estimates
atmosphere

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Baron, E., Branch, D., Hauschildt, P. H., Filippenko, A. V., Kirshner, R. P., Challis, P. M., ... Wheeler, J. C. (2000). Preliminary spectral analysis of the type II supernova 1999em. Astrophysical Journal, 545(1 PART 1), 444-448.
Baron, E. ; Branch, David ; Hauschildt, Peter H. ; Filippenko, Alexei V. ; Kirshner, R. P. ; Challis, P. M. ; Jha, Saurabh ; Chevalier, R. ; Fransson, Claes ; Lundqvist, Peter ; Garnavich, Peter ; Leibundgut, Bruno ; Mccray, R. ; Michael, E. ; Panagia, Nino ; Phillips, M. M. ; Pun, C. S.J. ; Schmidt, Brian ; Sonneborn, George ; Suntzeff, N. B. ; Wang, L. ; Wheeler, J. C. / Preliminary spectral analysis of the type II supernova 1999em. In: Astrophysical Journal. 2000 ; Vol. 545, No. 1 PART 1. pp. 444-448.
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Baron, E, Branch, D, Hauschildt, PH, Filippenko, AV, Kirshner, RP, Challis, PM, Jha, S, Chevalier, R, Fransson, C, Lundqvist, P, Garnavich, P, Leibundgut, B, Mccray, R, Michael, E, Panagia, N, Phillips, MM, Pun, CSJ, Schmidt, B, Sonneborn, G, Suntzeff, NB, Wang, L & Wheeler, JC 2000, 'Preliminary spectral analysis of the type II supernova 1999em', Astrophysical Journal, vol. 545, no. 1 PART 1, pp. 444-448.

Preliminary spectral analysis of the type II supernova 1999em. / Baron, E.; Branch, David; Hauschildt, Peter H.; Filippenko, Alexei V.; Kirshner, R. P.; Challis, P. M.; Jha, Saurabh; Chevalier, R.; Fransson, Claes; Lundqvist, Peter; Garnavich, Peter; Leibundgut, Bruno; Mccray, R.; Michael, E.; Panagia, Nino; Phillips, M. M.; Pun, C. S.J.; Schmidt, Brian; Sonneborn, George; Suntzeff, N. B.; Wang, L.; Wheeler, J. C.

In: Astrophysical Journal, Vol. 545, No. 1 PART 1, 10.12.2000, p. 444-448.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Preliminary spectral analysis of the type II supernova 1999em

AU - Baron, E.

AU - Branch, David

AU - Hauschildt, Peter H.

AU - Filippenko, Alexei V.

AU - Kirshner, R. P.

AU - Challis, P. M.

AU - Jha, Saurabh

AU - Chevalier, R.

AU - Fransson, Claes

AU - Lundqvist, Peter

AU - Garnavich, Peter

AU - Leibundgut, Bruno

AU - Mccray, R.

AU - Michael, E.

AU - Panagia, Nino

AU - Phillips, M. M.

AU - Pun, C. S.J.

AU - Schmidt, Brian

AU - Sonneborn, George

AU - Suntzeff, N. B.

AU - Wang, L.

AU - Wheeler, J. C.

PY - 2000/12/10

Y1 - 2000/12/10

N2 - We have calculated fast direct spectral model fits to two early-time spectra of the Type II plateau SN 1999em, using the SYNOW synthetic spectrum code. The first is an extremely early blue optical spectrum and the second a combined Hubble Space Telescope and optical spectrum obtained one week later. Spectroscopically this supernova appears to be a normal Type II, and these fits are in excellent agreement with the observed spectra. Our direct analysis suggests the presence of enhanced nitrogen. We have further studied these spectra with the full non-LTE general model atmosphere code PHOENIX. While we do not find confirmation for enhanced nitrogen (nor do we rule it out), we do require enhanced helium. An even more intriguing possible line identification is complicated Balmer and He I lines, which we show falls naturally out of the detailed calculations with a shallow density gradient. We also show that very early spectra such as those presented here combined with sophisticated spectral modeling allow an independent estimate of the total reddening to the supernova, since when the spectrum is very blue, dereddening leads to changes in the blue flux that cannot be reproduced by altering the "temperature" of the emitted radiation. These results are extremely encouraging since they imply that detailed modeling of early spectra can shed light on both the abundances and total extinction of SNe II, the latter improving their utility and reliability as distance indicators.

AB - We have calculated fast direct spectral model fits to two early-time spectra of the Type II plateau SN 1999em, using the SYNOW synthetic spectrum code. The first is an extremely early blue optical spectrum and the second a combined Hubble Space Telescope and optical spectrum obtained one week later. Spectroscopically this supernova appears to be a normal Type II, and these fits are in excellent agreement with the observed spectra. Our direct analysis suggests the presence of enhanced nitrogen. We have further studied these spectra with the full non-LTE general model atmosphere code PHOENIX. While we do not find confirmation for enhanced nitrogen (nor do we rule it out), we do require enhanced helium. An even more intriguing possible line identification is complicated Balmer and He I lines, which we show falls naturally out of the detailed calculations with a shallow density gradient. We also show that very early spectra such as those presented here combined with sophisticated spectral modeling allow an independent estimate of the total reddening to the supernova, since when the spectrum is very blue, dereddening leads to changes in the blue flux that cannot be reproduced by altering the "temperature" of the emitted radiation. These results are extremely encouraging since they imply that detailed modeling of early spectra can shed light on both the abundances and total extinction of SNe II, the latter improving their utility and reliability as distance indicators.

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Baron E, Branch D, Hauschildt PH, Filippenko AV, Kirshner RP, Challis PM et al. Preliminary spectral analysis of the type II supernova 1999em. Astrophysical Journal. 2000 Dec 10;545(1 PART 1):444-448.