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ASTR 545 Module 2 HR Diagram 08.1.1 Spectral Classes: (A) Write out the Spectral Classes from Hottest to Coolest Stars. Broadly

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ASTR 545 Module 2 HR Diagram 08.1.1 Spectral Classes: (A) Write out the Spectral Classes from Hottest to Coolest Stars. Broadly ASTR 545 Module 2 HR Diagram 08.1.1 Spectral Classes: (a) Write out the spectral classes from hottest to coolest stars. Broadly speaking, what are the primary spectral features that define each class? (b) What four macroscopic properties in a stellar atmosphere predominantly govern the relative strengths of features? (c) Briefly provide a qualitative description of the physical interdependence of these quantities (hint, don’t forget about free electrons from ionized atoms). 08.1.3 Luminosity Classes: (a) For an A star, write the spectral+luminosity class for supergiant, bright giant, giant, subgiant, and main sequence star. From the HR diagram, obtain approximate luminosities for each of these A stars. (b) Compute the radius and surface gravity, log g, of each luminosity class assuming M = 3M⊙. (c) Qualitative describe how the Balmer hydrogen lines change in strength and shape with luminosity class in these A stars as a function of surface gravity. 10.1.2 Spectral Classes and Luminosity Classes: (a,b,c,d) (a) What is the single most important physical macroscopic parameter that defines the Spectral Class of a star? Write out the common Spectral Classes of stars in order of increasing value of this parameter. For one of your Spectral Classes, include the subclass (0-9). (b) Broadly speaking, what are the primary spectral features that define each Spectral Class (you are encouraged to make a small table). How/Why (physically) do each of these depend (change with) the primary macroscopic physical parameter? (c) For an A type star, write the Spectral + Luminosity Class notation for supergiant, bright giant, giant, subgiant, main sequence star, and White Dwarf. From the HR diagram, obtain approximate luminosities and radii for each of these A stars. Present your work as a small table. (d) Qualitative describe how the Balmer hydrogen lines change in strength and shape in these A stars as a function of Luminosity Class. 10.3.3 4 A star on the HR diagram has T = 3000 K, L/L⊙ = 10 , and M/M⊙ = 3. (a) Compute log(g/g⊙) for this star. 1 (b) If the mass of this star were increased to M/M⊙ = 30, but the surface gravity was the same as in part (a), compute what the luminosity (L/L⊙) would be? 14.1.5 Luminosity Classes: (a) For an A star, write the spectral+luminosity class for supergiant, bright giant, giant, subgiant, main sequence star, and white dwarf. (b) From the HR diagram, obtain approximate luminosities for each of these A stars. (c) Given the luminosity and the typical temperature of an A star, compute the radius and surface gravity, log g, of each luminosity class assuming M = 3M⊙. Give your answers in solar units (R/R⊙ and g/g⊙). Show your work for a minimum of one stellar type and tabulate the stars by luminosity classes in order of increasing log g. (d) Qualitative describe how the equivalent widths and the wings of the Balmer hydrogen lines change with luminosity class in these A stars as a function of surface gravity. 16.2.4 = (14.1.5) Luminosity Classes: (a) For an A star, write the spectral+luminosity class for supergiant, bright giant, giant, subgiant, main sequence star, and white dwarf. (b) From the HR diagram, obtain approximate luminosities for each of these A stars. (c) Given the luminosity and the typical temperature of an A star, compute the radius and surface gravity, log g, of each luminosity class assuming M = 3M⊙. Give your answers in solar units (R/R⊙ and g/g⊙). Show your work for a minimum of one stellar type and tabulate the stars by luminosity classes in order of increasing log g. 2.
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