Type Ia SupernovaIlija Medan

What is a Type Ia Supernova?

• Progenitor thought to be a binary system• Two options:

• White Dwarf + Red Giant• White Dwarf + White Dwarf

• Supernova is thermonuclear explosion of white dwarf• Occurs as it approaches 1.38 !⊙ due

to accretion (less than Chandrasekhar limit)

• Thought to be due to sudden carbon fusion

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Why Use Type Ia?

Hamuy et al. (1995) Tammann & Schroder (1990)

Type Ia Supernova Type II Supernova

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More Evidence Of Common Peak Luminosities

• Branch & Tammann(1992) showed light curves for 22 Type IaSN• Good agreement

across all SN in the shape of light curve around peak

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More Evidence Of Common Peak Luminosities

• Saha et al. (1995) observed two Type IaSN in NGC 5253• Peaks were found to be !!"# = 8.33 ± 0.2 and !!"# = 8.56 ± 0.1• Less than 1! difference• Difference due to

reddening

Image Credit: ESA/Hubble & NASA 5

Distance Estimate – “Standard Candle”

• As peak luminosities are constant, Type IaSn are “standard candles” (i.e. brightness only depends on distance)

• Issue with standard candles:• Don’t have direct measurement of the

distance (so only know apparent brightness)• Need to calibrate relationship

A B

A

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Standard Candle Calibrator – Nearby Galaxies

• Find Type Ia SN that have occurred in the same galaxy• Saha et al. (1995) observed two Type Ia

SN in NGC 5253• What else is in NGC 5253?

• CEPHEIDS! (Another run on our ladder)• Find "!,#$% = −19.60 ± 0.11• Sources of Error:

• Tied to calibration of Cepheid distance relationship (usually based on distance to LMC)

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Standard Candle Calibrator – Thermal Emission

• Baade-Wesselink Method (Baade 1926, Wesselink 1946): If following are known for expanding object, can recover radius:• ""## at #$ and #%• $&'( at #$ and #%• %(')

• If radius and !!"" known can find luminosity (and distance)• Have to make assumptions about color-temperature relationship for SN

(blackbody, model atmospheres, etc.)• Find "#,%&' = −20.1 ± 0.7 (Branch et al. 1988)• Sources of error:

• Color-temperature relationship uncertain

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Standard Candle Calibrator – Ni-Co Decay

• SN Type Ia light curves caused by radioactive decay

• Peak luminosity can be related to ejected Ni mass and rise time

• Find "!,#$% = −19.4 ± 0.4(Harkness 1991)

• Sources of error:• Ni mass depends on mass of

progenitorImage Credit: Branch & Tammann (1992)

!"!" (##$%& =55 days)

%&!" (##$%& = 78 days)

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Standard Candle Calibrator – Modeling• Directly model the explosion

• Free parameters of more simple models:• Spectrum of supernova at various

times• Observed brightness with time for

various photometric bands

• Find "!,#$% = −19.4 ± 0.3(Branch 1992)

• Sources of error:• Physics of the explosion still not well

understood10

Video Credit: ASC / Alliances Center for Astrophysical Thermonuclear Flashes

Standard Candle Calibrator – Summary

Method Peak Absolute MagnitudeNearby Galaxies −19.60 ± 0.11

Thermal Emission −20.1 ± 0.7Ni-Co Decay −19.4 ± 0.4

Modeling −19.4 ± 0.3

In good agreement!

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What Distances Can We Probe?

• Using "! = −19.7 (and ignoring extinction and redshift correction), get expected apparent magnitude

• /! ≈ 20 corresponds to 1 billion pc• Farthest Type Ia SN discovered by

Dark Energy Survey at ~3×10'pc (Smith et al. 2018)

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Limitations of Using Type Ia SN

• We must observe a SN at peak luminosity to obtain a distance• For the size of the Virgo cluster,

rate is ~0.1 Type Ia SN per century

• Peak luminosity lasts on the order of a week, so takes either large surveys or luck to catch rare events!• e.g. Zwicky Transient Facility (ZTF)

and LSST

Image Credit: Maoz & Mannucci (2012) 13

Final (Large) Sources of Error

• Two important assumptions to use Type Ia SN as standard candles:1. All Type Ia SN progenitors are white dwarfs of the same mass at explosion• Evidence of “Super-Chandrasekhar-Mass” white dwarfs (Howell et al.

2006)• Type Iax SN are a class with white dwarf progenitors of lower mass

(Foley et al. 2013)2. The companion to the white dwarf has little effect on the SN peak

luminosity• Not sure what proportion of of Type Ia SN are from RG+WD systems or

WD+WD systems• WD+WD systems would result in merger and have higher mass (i.e.

higher peak luminosity) than expected

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Conclusions

• Type Ia SN can be used as standard candles to probe a large range of cosmological distances

• Multiple calibration methods provide similar peak luminosities

• Challenging to use though due to short window of the peak and small number of them

• Much is still unknown about these systems and the variety of them, which could lead to very large errors

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References• Baade, W. (1926). Über eine Möglichkeit, die Pulsationstheorie der Cephei-Veränderlichen zu prüten. Astronomische Nachrichten, 228(20),

359. • Branch, D., Drucker, W., & Jeffery, D. J. (1988). Differences among Expansion Velocities of Type IA Supernovae. ApJL, 330, L117.• Branch, D., & Tammann, G. ~A. (1992). Type IA supernovae as standard candles. ARA&A, 30, 359–389.• Foley, R. J., Challis, P. ~J., Chornock, R., Ganeshalingam, M., Li, W., Marion, G. ~H., … Soderberg, A. ~M. (2013). Type Iax Supernovae: A New

Class of Stellar Explosion. ApJ, 767(1), 57.• Gibson, B. ~K. (2000). The distance to the Large Magellanic Cloud. MEMSAI, 71, 693–700.• Hamuy, M., Phillips, M. ~M., Maza, J., Suntzeff, N. B., Schommer, R. ~A., & Aviles, R. (1995). A Hubble Diagram of Distant Type 1a Supernovae.

AJ, 109, 1.• Harkness, R. (1991). Type ia Supernovae. European Southern Observatory Conference and Workshop Proceedings, 37, 447.• Howell, D. A., Sullivan, M., Nugent, P. E., Ellis, R. S., Conley, A. J., Le Borgne, D., … Pritchet, C. J. (2006). The type Ia supernova SNLS-03D3bb

from a super-Chandrasekhar-mass white dwarf star. Nature, 443(7109), 308–311.• Maoz, D., & Mannucci, F. (2012). Type-Ia Supernova Rates and the Progenitor Problem: A Review. PASA, 29(4), 447–465.• Saha, A., Sandage, A., Labhardt, L., Schwengeler, H., Tammann, G. ~A., Panagia, N., & Macchetto, F. ~D. (1995). Discovery of Cepheids in NGC

5253: Absolute Peak Brightness of SN IA 1895B and SN IA 1972E and the Value of H 0. ApJ, 438, 8.• Smith, M., Sullivan, M., Nichol, R. ~C., Galbany, L., D’Andrea, C. ~B., Inserra, C., … DES Collaboration. (2018). Studying the Ultraviolet Spectrum

of the First Spectroscopically Confirmed Supernova at Redshift Two. ApJ, 854(1), 37.• Strom, R. G. (1988). Distances to the remnants of historical type I supernovae. MNRAS, 230, 331–344.• Tammann, G. ~A., & Schroeder, A. (1990). Supernova studies. V. The luminosity function of supernovae of type II. AAP, 236, 149.• Wesselink, A. ~J. (1946). The observations of brightness, colour and radial velocity of Cephei and the pulsation hypothesis (Errata: 10 258,

310). BAIN, 10, 91. 16