Recent Atomic Data for Cr <scp>ii</scp> Improves Non-LTE Model for Sirius A Spectrum

Abstract Sirius A ( α Canis Majoris), with its slow rotation and stable atmospheric conditions, serves as an ideal candidate for 1D stellar atmosphere spectral synthesis. Its mass, radius, and surface gravity are known to great precision (≃1%), however, its elemental composition is one of its most uncertain parameters. To improve the accuracy of spectral synthesis, we have updated the Cr ii model atom used in the PHOENIX stellar atmosphere code to include the latest atomic data available in the literature. Comparison of the synthetic non-local thermodynamic equilibrium spectrum with the observed spectrum, from the Very Large Telescope Ultraviolet and Visible Echelle Spectrograph, shows great improvement for four lines: 3084.46 Å and 3173.56 Å, 4539.59 Å, and 4565.74 Å relative to earlier models with less accurate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo>(</mml:mo> <mml:mi>g</mml:mi> <mml:mi>f</mml:mi> <mml:mo>)</mml:mo> </mml:math> values. These Cr ii lines are in need of experimental <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo>(</mml:mo> <mml:mi>g</mml:mi> <mml:mi>f</mml:mi> <mml:mo>)</mml:mo> </mml:math> values: 3495.38, 4150.99, 4224.85, and 4912.45 Å.