Mira B

{{Starbox begin

|title=Mira B (VZ Ceti)}}

{{Starbox image

|caption=The red giant star Mira (right), and its companion Mira B on the left. Taken on December 11, 1995, by the Hubble Space Telescope using the Faint Object Camera.

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{{Starbox observe

|epoch=J2000

|constell=Cetus

|ra={{RA|02|19|20.80}}{{cite journal|title=VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications|author=Skiff, B. A.|journal=VizieR On-line Data Catalog|volume=1|date=2014|bibcode=2014yCat....1.2023S}}

|dec={{DEC|−02|58|40.0}}

|appmag_v=9.5–12.0{{cite journal|title=An Electronic Version of the Second Volume of the General Catalogue of Variable Stars with Improved Coordinates|author1=Samus', N. N.|display-authors=etal|journal=Astronomy Letters|volume=29|issue=7|pages=468–479|date=2003|bibcode=2003AstL...29..468S|doi=10.1134/1.1589864|s2cid=16299532}}

}}

{{Starbox character

|class=DA{{cite journal|title=Observations of rapid blue variables – VIII. The companion to Mira|author=Warner, B.| author-link=Brian Warner (astronomer)|journal=Monthly Notices of the Royal Astronomical Society|volume=159|pages=95–100 |date=1972 |bibcode=1972MNRAS.159...95W |doi=10.1093/mnras/159.1.95|doi-access=free}}

}}

{{Starbox astrometry

|dist_ly=approx. 300{{Cite journal|first1=F.|last1=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752|s2cid=18759600 }}

|dist_pc=approx. 90

}}

{{Starbox catalog

|names=VZ Cet, ο Cet B, WDS J02193-0259Ab, CCDM J02194-0258P, WD 0216-032

}}

Mira B, also known as VZ Ceti, is the companion star to the variable star Mira, separated by around {{Val|100|ul=AU}}. Suspected as early as 1918, it was visually confirmed in 1923 by Robert Grant Aitken, and has been observed more or less continually since then, most recently by the Chandra X-Ray Observatory.{{cite book|author=Robert Burnham|title=Burnham's Celestial Handbook, Volume One: An Observer's Guide to the Universe Beyond the Solar System|url=https://books.google.com/books?id=z3_CAgAAQBAJ|date=15 April 2013|publisher=Courier Corporation|isbn=978-0-486-31902-5}}

Long known to be erratically variable itself, its fluctuations seem to be related to its accretion of matter from Mira's stellar wind, which makes it a symbiotic star.{{cite book|author=James B. Kaler|title=The Hundred Greatest Stars|url=https://books.google.com/books?id=jmoQBwAAQBAJ|date=7 May 2006|publisher=Springer Science & Business Media|isbn=978-0-387-21625-6}}

Orbit

Its orbit around Mira is poorly known; the most recent estimate listed in the Sixth Catalog of Orbits of Visual Binary Stars gives an orbital period of roughly 500 years, with a periastron around the year 2285. Assuming the distance in the Hipparcos catalog and orbit are correct, Mira A and B are separated by an average of 100 AU.{{cite web|url=http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6|title=Sixth Catalog of Orbits of Visual Binary Stars|publisher=United States Naval Observatory|access-date=21 June 2017|archive-date=1 August 2017|archive-url=https://web.archive.org/web/20170801102553/http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6|url-status=dead}}

Current research

File:VZCetLightCurve.png light curves for Mira B (VZ Ceti), adapted from Sokoloski and Bildsten (2010)]]

In January 2007, astronomers at the Keck Observatory announced the discovery of a protoplanetary disk around Mira B. Discovered via infrared data, the disk is apparently derived from captured material from Mira itself; Mira B accretes as much as one percent of the matter lost by its primary. Though planetary formation is perhaps unlikely as long as the disk is in active accretion, it may proceed apace once Mira A completes its red giant phase and becomes a white dwarf remnant.{{cite journal|doi=10.1086/517993|title=Born-Again Protoplanetary Disk around Mira B|journal=The Astrophysical Journal|volume=662|pages=651–657|year=2007|last1=Ireland|first1=M. J|last2=Monnier|first2=J. D|last3=Tuthill|first3=P. G|last4=Cohen|first4=R. W|last5=De Buizer|first5=J. M|last6=Packham|first6=C|last7=Ciardi|first7=D|last8=Hayward|first8=T|last9=Lloyd|first9=J. P|issue=1|bibcode=2007ApJ...662..651I|arxiv=astro-ph/0703244|s2cid=16694}}

Several factors, such as low x-ray luminosity, suggest that Mira B is actually a normal main-sequence star of spectral type K and roughly 0.7 solar mass, rather than a white dwarf as first envisioned. However, a 2010 analysis of rapid optical brightness variations has indicated that Mira B is, in fact, a white dwarf.{{cite journal |arxiv=1009.2509 |author1=J. L. Sokoloski |author2=Lars Bildsten |title=Evidence for the White Dwarf Nature of Mira B |date=2010 |doi=10.1088/0004-637X/723/2/1188 |volume=723 |issue=2 |journal=The Astrophysical Journal |pages=1188–1194 |bibcode=2010ApJ...723.1188S|s2cid=119247560 }}

External links

[http://www.aavso.org/vstar/vsots/1298.shtml From the AAVSO Variable Star of the Month: Mira] {{Webarchive|url=https://web.archive.org/web/20030705131018/http://www.aavso.org/vstar/vsots/1298.shtml |date=2003-07-05 }}
[https://web.archive.org/web/20090412084731/http://ad.usno.navy.mil/wds/orb6.html Sixth Orbit Catalog]
[http://chandra.harvard.edu/photo/2005/mira/ Chandra Photo Album, Mira press release]
[https://arxiv.org/abs/astro-ph/0703244 Born Again Protoplanetary Disk Around Mira B]

References

Category:Binary stars

Category:White dwarfs

Category:Cetus

Ceti, Omicron, B

Ceti, VZ

Category:Astronomical objects discovered in 1923