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Spectroscopy - faint target v bright moonlight


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An example of how tolerant spectroscopy can be of  bright sky conditions.  This supernova SN 2020uxz has now faded to mag 16.5.  Despite the sky background being around 5x brighter than the spectrum (Taken using an ALPY modified for faint objects at lower resolution) there is still enough signal to identify it as a type Ia around 70 days past maximum, matching for example SN 2002bo from SNID (red) at a similar age.

Cheers

Robin

 

 

SN2020uxb_20210101_ALPY200.png

sn2020uxz_snidfit_2002bo.png

Edited by robin_astro
typo
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Here's another one from last night. SN 2020adow discovered a week ago in a relatively nearby galaxy KUG 0830+278 (redshift 0.0075) 

https://www.wis-tns.org/object/2020adow

SN2020adow_SNIDfit_SN1994I.png.ed484002f7f55e410e03d7c7b7a74d55.png

Here overlaid on  matching type Ic supernova SN1994I, and below compared with the professional spectrum used  to classify it 

sn2020adow_20210101_956_Leadbeater.png.47cb9000c51a309d66d5f17dcf422a84.png

Type Ic are a relatively less common type of  so called "Stripped Envelope" Core Collapse Supernova where the exploding massive star has already lost its Hydrogen and Helium so these do not appear in the spectrum. The narrow line at H alpha (at 6612A, red-shifted from 6563A) is from the host galaxy which is completely outshone by the exceptionally powerful supernova, here identified  as a broad lined (BL) variant due to the higher than usual velocity of the explosion. The magnitude here was ~14.5. Note how my spectrum appears to be redshifted relative to the professional spectrum taken a few days earlier. This is because we are now seeing slower moving material in the spectrum (less blue shifted) compared with a few days earlier.

Cheers

Robin

 

 

Edited by robin_astro
typo
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And finally...   

A brand new one to kick  off the new year.  AT2021K discovered yesterday at mag 15.7 in galaxy MCG +06-30-084 

https://www.wis-tns.org/object/2021k

"AT" signifies it has not yet been confirmed and classified as a supernova.  It is another who's light dominates its parent galaxy as seen in the discovery image

https://alerce.online/object/ZTF21aaabvjk

My spectrum from last night is inconclusive so I cannot officially classify it.  I suspect it may be a type Ia , (the thermonuclear detonation of a white dwarf in a binary system) though the usual identifying feature (Si II absorption at around 6300A) is not obvious

AT2021K_SNIDfit_Ia.png.509e97f51aa607c0854f8048e072a762.png

Cheers

Robin

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On 02/01/2021 at 22:52, robin_astro said:

My spectrum from last night is inconclusive so I cannot officially classify it.  I suspect it may be a type Ia 

 

Unfortunately the weather prevented me from getting another shot at this and it has now been classified (unusually from a spectrum at the UV/blue end of the spectrum). My suspicion that it was a type Ia turned out to be  correct though

https://www.wis-tns.org/object/2021K

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