4 Draconis

{{Starbox image

| image = 250px

| caption = Light curves for CQ Draconis, adapted from Skopal et al. (1992) The brightening seen (most clearly in the ultraviolet) after June 1990 occurred shortly after the periastron passage.

}}

{{Starbox observe

| epoch = J2000.0

| ra = {{RA|12|30|06.66200}}

| dec = {{DEC|+69|12|03.9742}}

| appmag_v = 4.90 - 5.12

| constell = Draco

}}

{{Starbox character

| class = M3+ IIIa

| b-v =

| u-b =

| variable = Z Andromedae

}}

{{Starbox astrometry

| radial_v = −15

| prop_mo_ra = {{val|-57.311|0.214}}

| prop_mo_dec = {{val|-50.365|0.219}}

| parallax = 5.7233

| p_error = 0.1880

| parallax_footnote =

| absmag_v = −1.37

}}

{{Starbox orbit

| reference =

| primary = 4 Draconis A (red giant)

| name = 4 Draconis B

| period =

| period_unitless = {{val|fmt=commas|1703|3|ul=d}}

| axis =

| axis_unitless = {{val|82|4|ul=Gm}} ( a⋅sin(i) )

| eccentricity = {{val|0.30|0.05}}

| inclination =

| node =

| periastron = 2442868.5

| periarg =

| periarg_primary = {{val|244|9}}

| k1 = {{val|3.67|0.19}}

| k2 =

}}

{{Starbox detail

| component1 = red giant

| mass = {{val|1.64|0.2}}

| radius = {{val|111.0|9.30|11.2}}

| temperature = {{val|3718|69|fmt=commas}}

| gravity = 1.24

| luminosity = {{val|2122|419|fmt=commas}}

| age_gyr={{val|1.97|0.57}}

| component2 = white dwarf

| mass2 = ~0.8

| temperature2 = {{val|fmt=commas|20000|3000}}

}}

{{Starbox catalog

| names = CQ Dra, HD 108907, HR 4765, HIP 60998, SAO 15816

}}

{{Starbox reference

| Simbad = CQ+Dra

}}

4 Draconis, also known as HR 4765 and CQ Draconis, is a star about 570 light years from the Earth, in the constellation Draco. It is a 5th magnitude star, so it will be faintly visible to the naked eye of an observer far from city lights. It is a variable star, whose brightness varies slightly from 4.90 to 5.12 over a period of 4.66 years.

In 1967, Olin Eggen discovered that 4 Draconis is a variable star, during a multicolor photometric survey of red stars. In 1973 it was given the variable star designation CQ Draconis.

Until the year 1985, 4 Draconis was thought to be a normal red giant star. In 1985, Dieter Reimers announced that the International Ultraviolet Explorer had detected a hot companion to the red giant, which itself appeared to be a binary cataclysmic variable star, making the complete system a triple star. However a 2003 study by Peter Wheatley et al., who examined ROSAT X-ray data for the star, concluded that the hot companion was more apt to be a single white dwarf, rather than a binary, and that the white dwarf is accreting material from the red giant. There does not yet appear to be a consensus about the multiplicity; some later studies consider 4 Draconis to be a binary, and some a triple.

In 1987, Alexander Brown announced that 6 cm wavelength radio emission had been detected by the Very Large Array. The strength of the radio emission was variable on a timescale of weeks to months.

It is possible that an outburst of 4 Draconis was the "guest star" reported by Chinese astronomers in the year 369 CE, in the constellation Zigong.

References

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Category:Draco (constellation)

060998

108907

Draconis, CQ

Category:Z Andromedae variables

Draconis, 4

Category:M-type giants