BD Camelopardalis
Encyclopedia
BD Camelopardalis is an S star and symbiotic star in the constellation Camelopardalis
. It was recognized as a spectroscopic binary star in 1922, and its orbital solution published in 1984; it has a 596-day orbital period. A spectroscopic composition analysis was done of the red giant primary star in 1986.
Although the star's spectrum shows the spectral features of zirconium oxide which define spectral class S, BD Cam shows no technetium
lines in its spectrum. It is believed to be an "extrinsic" S star, one whose s-process
element excesses originate in a binary companion star. The system displays only minimal variations in the visible, but the presence of the companion and its interactions with the stellar wind
of the visible red giant
makes for easily observed time-variable spectral features in the ultraviolet
and in the near infrared
spectral line of helium
.
At times BD Cam is the brightest S star in the visible sky, because other bright S stars are mira variable
s or other types of variable star
with large changes in apparent brightness. Its own brightness variability in the visible part of the spectrum is modest.
" On the basis of the measurement of radial velocities of the line components it is concluded that the helium emission originates in the vicinity of the inner Lagrangian point of the system, indicating a gas motion from the red giant primary, directed to the secondary, with a velocity of about 5 km/s. At the same time, there is a high-velocity, hot wind outwards from the primary red giant with a velocity of about 50 km/s. " -Shcherbakov, A. G. and Tuominen, I.
" However, HR 1105 appears to have a highly variable UV companion. In 1982, no UV flux was discerned for this system, but by 1986 C IV was strong, increasing by a factor of 3 in 1987 with prominent lines of Si III, C III, O III, Si IV, and N V. " - Ake, Thomas B., III; Johnson, Hollis R. and Perry, Benjamin F., Jr.
Camelopardalis
Camelopardalis is a large but faint constellation in the northern sky. The constellation was introduced in 1612 by Petrus Plancius. Some older astronomy books give an alternative spelling of the name, Camelopardus.-Etymology:...
. It was recognized as a spectroscopic binary star in 1922, and its orbital solution published in 1984; it has a 596-day orbital period. A spectroscopic composition analysis was done of the red giant primary star in 1986.
Although the star's spectrum shows the spectral features of zirconium oxide which define spectral class S, BD Cam shows no technetium
Technetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...
lines in its spectrum. It is believed to be an "extrinsic" S star, one whose s-process
S-process
The S-process or slow-neutron-capture-process is a nucleosynthesis process that occurs at relatively low neutron density and intermediate temperature conditions in stars. Under these conditions the rate of neutron capture by atomic nuclei is slow relative to the rate of radioactive beta-minus decay...
element excesses originate in a binary companion star. The system displays only minimal variations in the visible, but the presence of the companion and its interactions with the stellar wind
Stellar wind
A stellar wind is a flow of neutral or charged gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.Different types of stars have...
of the visible red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
makes for easily observed time-variable spectral features in the ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
and in the near infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
spectral line of helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
.
At times BD Cam is the brightest S star in the visible sky, because other bright S stars are mira variable
Mira variable
Mira variables , named after the star Mira, are a class of pulsating variable stars characterized by very red colors, pulsation periods longer than 100 days, and light amplitudes greater than one magnitude in infrared and 2.5 magnitude in visual...
s or other types of variable star
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
with large changes in apparent brightness. Its own brightness variability in the visible part of the spectrum is modest.
" On the basis of the measurement of radial velocities of the line components it is concluded that the helium emission originates in the vicinity of the inner Lagrangian point of the system, indicating a gas motion from the red giant primary, directed to the secondary, with a velocity of about 5 km/s. At the same time, there is a high-velocity, hot wind outwards from the primary red giant with a velocity of about 50 km/s. " -Shcherbakov, A. G. and Tuominen, I.
" However, HR 1105 appears to have a highly variable UV companion. In 1982, no UV flux was discerned for this system, but by 1986 C IV was strong, increasing by a factor of 3 in 1987 with prominent lines of Si III, C III, O III, Si IV, and N V. " - Ake, Thomas B., III; Johnson, Hollis R. and Perry, Benjamin F., Jr.