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EF Eridani

{{short description|Star in the constellation Eridanus}}

{{Starbox begin}}

{{Starbox image

| image = 250px

| caption = Visual band light curves for EF Eridani, adapted from Williams and Hiltner (1980)

}}

{{Starbox observe

| epoch = J2000.0

| constell = Eridanus

| ra = {{RA|03|14|13.25262}}

| dec = {{DEC|-22|35|42.9001}}

| appmag_v = 14.5–17.3

}}

{{Starbox character

| class =

| variable = E+XM{{cite web | title=Query= EF Eri

| url=http://www.sai.msu.su/gcvs/cgi-bin/search.cgi?search=EF+Eri

| publisher=Centre de Données astronomiques de Strasbourg

| work=General Catalogue of Variable Stars | access-date=2009-12-17}}

}}

{{Starbox astrometry

| radial_v = 70

| prop_mo_ra = 137.993

| prop_mo_dec = -55.971

| pm_footnote =

| parallax = 6.2327

| p_error = 0.1417

| parallax_footnote =

}}

{{Starbox catalog

| names = GSC 6439.00120, X 03116-227}}

{{Starbox reference

| Simbad = EF+Eri

}}

{{Starbox end}}

EF Eridani (abbreviated EF Eri, sometimes incorrectly referred to as EF Eridanus) is a variable star of the type known as polars, AM Herculis stars, or magnetic cataclysmic variable stars. Historically it has varied between apparent magnitudes 14.5 and 17.3, although since 1995 it has generally remained at the lower limit. The star system consists of a white dwarf with a substellar-mass former star in orbit.

EF Eridani B

The substellar mass in orbit around the white dwarf is a star that lost all of its gas to the white dwarf. What remains is an object with a mass of 0.05 solar masses ({{Solar mass|link=y}}), or about 53 Jupiter masses ({{Jupiter mass|link=yes}}), which is too small to continue fusion, and does not have the composition of a super-Jupiter, brown dwarf, or white dwarf. There is no category for such a stellar remnant.

It is hypothesized that 500 million years ago, the white dwarf started to cannibalize its partner, when they were separated by 7 million km. As it lost mass, the regular star spiraled inward. Today, they are separated by a mere 700,000 km for an orbital period of {{val|81|u=min}}. The orbit is expected to continue to shrink due to gravitational radiation.{{cite journal | title=Evidence for a substellar secondary in the magnetic cataclysmic binary EF Eridani | author=Beuermann, K. | author2=Wheatley, P. | author3=Ramsay, G. | author4=Euchner, F. | author5=Gänsicke, B. T. | journal=Astronomy and Astrophysics Letters| volume=354 | pages=L49–L52 | date=February 2000 | bibcode=2000A&A...354L..49B|arxiv = astro-ph/0001183 }}

See also

References

{{reflist|refs=

{{Cite Gaia DR3|5099482805904892288}}

{{cite web

| url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=EF+Eri

| title =V* EF Eri – Nova-like Star

| publisher=Centre de Données astronomiques de Strasbourg

| work=SIMBAD

| access-date=2009-12-17}}

{{cite journal |last1=Williams |first1=G. |last2=Hiltner |first2=W. A. |title=Light curve of the optical counterpart of 2A 0311-227 |journal=Publications of the Astronomical Society of the Pacific |date=April 1980 |volume=92 |pages=178–182 |doi=10.1086/130643 |bibcode=1980PASP...92..178W |s2cid=120568192 |doi-access=free }}

}}

External links

  • [https://web.archive.org/web/20041012120611/http://www.cnn.com/2004/TECH/space/10/05/space.star.reut/index.html (CNN) Faded star defies description]
  • [https://web.archive.org/web/20030512095207/http://www.aavso.org/cgi-bin/searchcharts3.pl?name=EF+ERI AAVSO charts for EF Eridani]

{{Stars of Eridanus}}

{{DEFAULTSORT:EF Eridani}}

Category:Polars (cataclysmic variable stars)

Category:Eridanus (constellation)

Eridani, EF

Category:Eclipsing binaries