SN 2013aa and SN 2017cbv: Two Sibling Type Ia Supernovae in the spiral galaxy NGC 5643

Understand

We present photometric and spectroscopic observations of SN 2013aa and SN 2017cbv, two nearly identical type Ia supernovae (SNe Ia) in the host galaxy NGC 5643.

• The optical photometry has been obtained using the same telescope and instruments used by the Carnegie Supernova Project.
• This eliminates most instrumental systematics and provides light curves in a stable and well-understood photometric system.
• Having the same host galaxy also eliminates systematics due to distance and peculiar velocity, providing an opportunity to directly test the relative precision of SNe Ia as standard candles.