Phillips relationship

The Phillips relationship (according to M. Phillips, who first described it in 1993) describes an empirical relationship between the course of the light curves of thermonuclear supernovae of type Ia and the absolute brightness . With the help of the Phillips relationship, astronomical distance determination could be extended to cosmological distances with high accuracy and led to the discovery of the accelerated expansion of the universe .

statement

According to the Phillips relationship, there is a connection between the absolute brightness and the decrease in brightness in the blue filter of the UBV system 15 days after the maximum of the supernova light curve. ${\displaystyle M}$ ${\displaystyle \Delta {m}_{15}}$

The Phillips relationship was later developed into a multi-color light curve method, which is less dependent on the correction of the extinction . The absolute visual brightness at the maximum is therefore:

${\displaystyle M_{\mathrm {max} }(V)=-19.504+0.736\cdot \Delta m_{15}(B)+0.182\cdot \Delta m_{15}^{2}(B)+5\cdot \log(H_{0})}$

${\displaystyle H_{0}}$is Hubble's constant in units of 65 km / s per megaparsec and is used to correct the accelerated expansion of the universe. The accuracy of the multi-color light curve method is 0.1  mag .

The Phillips relationship does not apply to the under-luminous supernova of the Iax type and the over-luminous super-Chandrasekhar supernovae . These thermonuclear supernovae can be identified as non-standard type Ia supernova on the basis of the brightness curve.

interpretation

The light curves of supernovae are driven by the radioactive decay of ⁵⁶ Ni . The amount of radioactive nickel determines the temperature of the supernovae photosphere and influences the opacity of the stellar atmosphere . As the temperature rises, the opacity increases, so that more energy is retained in the atmosphere. This accelerates the decrease in brightness and the energy is radiated later.

A small group of Type Ia supernovae, such as B. SN 2001ay, but do not follow the Phillips relationship. The absolute brightness of these supernovae corresponds to that of other standard SN-Ia, while the decrease in brightness is significantly slower. This is interpreted as the result of an unusual chemical composition of the precursor star, according to which the exploded white dwarf is said to have consisted of over 80 percent carbon .

Individual evidence

1. ↑ Phillips, MM: The absolute magnitudes of Type IA supernovae . In: Astrophysical Journal Letters . tape 413 , 1993, pp. L105-L108 , doi : 10.1086 / 186970 .
2. ↑ Richard de Grijs: An Introduction to Distance Measurement in Astronomy . Wiley, Chichester 2011, ISBN 978-0-470-51179-4 , pp. 188-198 .
3. ^ Saurabh Jha, Adam G. Riess and Robert P. Kirshner: Improved Distances to Type Ia Supernovae with Multicolor Light-Curve Shapes: MLCS2k2 . In: Astrophysical Journal . tape 659 , 2007, p. 122-148 , doi : 10.1086 / 512054 .
4. ^ Ryan J. Foley et al .: TYPE Iax SUPERNOVAE: A NEW CLASS OF STELLAR EXPLOSION . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1212.2209v2 .
5. ↑ Upasana Das, Banibrata Mukhopadhyay: New mass limit for white dwarfs: super-Chandrasekhar type Ia supernova as a new standard candle . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.5965 .
6. ^ B. Sadler et al .: Constraining the Properties of SNe Ia Progenitors from Light Curves . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1109.3629 .
7. ↑ E. Baron, P. Hoeflich, K. Krisciunas, I. Dominguez, AM Khokhlov, MM Phillips, N. Suntzeff, L. Wang: A Physical Model for SN 2001ay, a normal, bright, extremely slowly declining Type Ia supernova . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1205.0814v1 .