ATLAS filters

The typically used ATLAS filters are non-standard, 'cyan' ('c-band') and 'orange' ('o-band'), covering 4200 - 6500 and 5600 - 8200 Angstrom, respectively. 'Cyan' is roughly equivalent to a broad 'g+r' filter, and 'orange' is a broad 'r+i' filter.

Some tests have been performed to compare these filters to the more commonly used ones. This was done using a template SN Ia at max. and a SN characterised by a blue continuum (LSQ13ddu). The magnitude offsets for the spectra at z=0 and z=0.1 were calculated and the values are given in Table 1. The offset between the cyan and orange filters for both objects is that the flux through the 'orange' filter is ~0.2 mag fainter than through the 'cyan' filter.


Table 1. Offsets from B band magnitude for the two ATLAS filters for a SN Ia and LSQ13ddu at two redshifts, z=0 and z=0.1.
Type
 Redshift Cyan  offset (mag)*  
Orange
offset (mag)*
SN Ia (max.)
 00.2
0.4
SN Ia (max.)
 0.1-0.1  0.1

LSQ13ddu (early)$
 0        0.1
0.3
LSQ13ddu (early)$   
 0.1        0.1
 0.2

*Offsets are with respect to the B band
$LSQ13ddu is dominated by a blue continuum at early times (seen in many young CC SNe)




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