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Title: Understanding type Ia supernovae through their U-band spectra

Abstract

Observations of type Ia supernovae (SNe Ia) can be used to derive accurate cosmological distances through empirical standardization techniques. Despite this success neither the progenitors of SNe Ia nor the explosion process are fully understood. The U-band region has been less well observed for nearby SNe, due to technical challenges, but is the most readily accessible band for high-redshift SNe. Using spectrophotometry from the Nearby Supernova Factory, we study the origin and extent of U-band spectroscopic variations in SNe Ia and explore consequences for their standardization and the potential for providing new insights into the explosion process. We divide the U-band spectrum into four wavelength regions λ(uNi), λ(uTi), λ(uSi) and λ(uCa). Two of these span the Ca H&K λλ 3934, 3969 complex. We employ spectral synthesis using SYNAPPS to associate the two bluer regions with Ni/Co and Ti. The flux of the uTi feature is an extremely sensitive temperature/luminosity indicator, standardizing the SN peak luminosity to 0.116 ± 0.011 mag root mean square (RMS). A traditional SALT2.4 fit on the same sample yields a 0.135 mag RMS. Standardization using uTi also reduces the difference in corrected magnitude between SNe originating from different host galaxy environments. Early U-band spectra can bemore » used to probe the Ni+Co distribution in the ejecta, thus offering a rare window into the source of light curve power. The uCa flux further improves standardization, yielding a 0.086 ± 0.010 mag RMS without the need to include an additional intrinsic dispersion to reach χ 2/dof ~ 1. Here, this reduction in RMS is partially driven by an improved standardization of Shallow Silicon and 91T-like SNe« less

Authors:
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Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of California, Oakland, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Org.:
The Nearby Supernova Factory
OSTI Identifier:
1543825
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Astronomy and Astrophysics
Additional Journal Information:
Journal Volume: 614; Journal ID: ISSN 0004-6361
Publisher:
EDP Sciences
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Astronomy & Astrophysics; supernovae: general; cosmology: observations; dark energy

Citation Formats

Nordin, J., Aldering, G., Antilogus, P., Aragon, C., Bailey, S., Baltay, C., Barbary, K., Bongard, S., Boone, K., Brinnel, V., Buton, C., Childress, M., Chotard, N., Copin, Y., Dixon, S., Fagrelius, P., Feindt, U., Fouchez, D., Gangler, E., Hayden, B., Hillebrandt, W., Kim, A., Kowalski, M., Kuesters, D., Leget, P. -F., Lombardo, S., Lin, Q., Pain, R., Pecontal, E., Pereira, R., Perlmutter, S., Rabinowitz, D., Rigault, M., Runge, K., Rubin, D., Saunders, C., Smadja, G., Sofiatti, C., Suzuki, N., Taubenberger, S., Tao, C., and Thomas, R. C. Understanding type Ia supernovae through their U-band spectra. United States: N. p., 2018. Web. doi:10.1051/0004-6361/201732137.
Nordin, J., Aldering, G., Antilogus, P., Aragon, C., Bailey, S., Baltay, C., Barbary, K., Bongard, S., Boone, K., Brinnel, V., Buton, C., Childress, M., Chotard, N., Copin, Y., Dixon, S., Fagrelius, P., Feindt, U., Fouchez, D., Gangler, E., Hayden, B., Hillebrandt, W., Kim, A., Kowalski, M., Kuesters, D., Leget, P. -F., Lombardo, S., Lin, Q., Pain, R., Pecontal, E., Pereira, R., Perlmutter, S., Rabinowitz, D., Rigault, M., Runge, K., Rubin, D., Saunders, C., Smadja, G., Sofiatti, C., Suzuki, N., Taubenberger, S., Tao, C., & Thomas, R. C. Understanding type Ia supernovae through their U-band spectra. United States. doi:10.1051/0004-6361/201732137.
Nordin, J., Aldering, G., Antilogus, P., Aragon, C., Bailey, S., Baltay, C., Barbary, K., Bongard, S., Boone, K., Brinnel, V., Buton, C., Childress, M., Chotard, N., Copin, Y., Dixon, S., Fagrelius, P., Feindt, U., Fouchez, D., Gangler, E., Hayden, B., Hillebrandt, W., Kim, A., Kowalski, M., Kuesters, D., Leget, P. -F., Lombardo, S., Lin, Q., Pain, R., Pecontal, E., Pereira, R., Perlmutter, S., Rabinowitz, D., Rigault, M., Runge, K., Rubin, D., Saunders, C., Smadja, G., Sofiatti, C., Suzuki, N., Taubenberger, S., Tao, C., and Thomas, R. C. Fri . "Understanding type Ia supernovae through their U-band spectra". United States. doi:10.1051/0004-6361/201732137. https://www.osti.gov/servlets/purl/1543825.
@article{osti_1543825,
title = {Understanding type Ia supernovae through their U-band spectra},
author = {Nordin, J. and Aldering, G. and Antilogus, P. and Aragon, C. and Bailey, S. and Baltay, C. and Barbary, K. and Bongard, S. and Boone, K. and Brinnel, V. and Buton, C. and Childress, M. and Chotard, N. and Copin, Y. and Dixon, S. and Fagrelius, P. and Feindt, U. and Fouchez, D. and Gangler, E. and Hayden, B. and Hillebrandt, W. and Kim, A. and Kowalski, M. and Kuesters, D. and Leget, P. -F. and Lombardo, S. and Lin, Q. and Pain, R. and Pecontal, E. and Pereira, R. and Perlmutter, S. and Rabinowitz, D. and Rigault, M. and Runge, K. and Rubin, D. and Saunders, C. and Smadja, G. and Sofiatti, C. and Suzuki, N. and Taubenberger, S. and Tao, C. and Thomas, R. C.},
abstractNote = {Observations of type Ia supernovae (SNe Ia) can be used to derive accurate cosmological distances through empirical standardization techniques. Despite this success neither the progenitors of SNe Ia nor the explosion process are fully understood. The U-band region has been less well observed for nearby SNe, due to technical challenges, but is the most readily accessible band for high-redshift SNe. Using spectrophotometry from the Nearby Supernova Factory, we study the origin and extent of U-band spectroscopic variations in SNe Ia and explore consequences for their standardization and the potential for providing new insights into the explosion process. We divide the U-band spectrum into four wavelength regions λ(uNi), λ(uTi), λ(uSi) and λ(uCa). Two of these span the Ca H&K λλ 3934, 3969 complex. We employ spectral synthesis using SYNAPPS to associate the two bluer regions with Ni/Co and Ti. The flux of the uTi feature is an extremely sensitive temperature/luminosity indicator, standardizing the SN peak luminosity to 0.116 ± 0.011 mag root mean square (RMS). A traditional SALT2.4 fit on the same sample yields a 0.135 mag RMS. Standardization using uTi also reduces the difference in corrected magnitude between SNe originating from different host galaxy environments. Early U-band spectra can be used to probe the Ni+Co distribution in the ejecta, thus offering a rare window into the source of light curve power. The uCa flux further improves standardization, yielding a 0.086 ± 0.010 mag RMS without the need to include an additional intrinsic dispersion to reach χ2/dof ~ 1. Here, this reduction in RMS is partially driven by an improved standardization of Shallow Silicon and 91T-like SNe},
doi = {10.1051/0004-6361/201732137},
journal = {Astronomy and Astrophysics},
number = ,
volume = 614,
place = {United States},
year = {2018},
month = {6}
}

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