99 Aquarii

{{short description|Orange-hued giant star in the constellation Aquarius}}

{{about|b² Aquarii|other star systems with this Bayer designation|b Aquarii}}

{{Starbox begin

| name = 99 Aquarii

}}

{{Starbox image

| image =

File:Aquarius IAU.svg

12px

| caption = Location of 99 Aquarii (circled)

}}

{{Starbox observe

| epoch = J2000

| ra = {{RA|23|26|02.7857}}

| dec = {{DEC|−20|38|31.251}}

| appmag_v = 4.37

| constell = Aquarius

}}

{{Starbox character

| class = K4 III

| b-v = +1.431

| u-b = +1.815

| variable = Suspected

}}

{{Starbox astrometry

| radial_v = +15.7

| prop_mo_ra = −50.72

| prop_mo_dec = −64.22

| parallax = 11.51

| p_error = 0.21

| parallax_footnote =

| absmag_v =

}}

{{Starbox detail

| mass =

| radius = 33

| luminosity =

| temperature = 3980

| metal_fe = −0.20

| gravity = 1.66

| rotational_velocity =

| age_myr =

}}

{{Starbox catalog

| names= BD−21 6420, HD 220704, HIP 115669, HR 8906, NSV 14554, SAO 191900.

}}

99 Aquarii (abbreviated 99 Aqr) is a star in the equatorial constellation of Aquarius. 99 Aquarii is the Flamsteed designation, although it also bears the Bayer designation b² Aquarii. It is visible to the naked eye with an apparent visual magnitude of 4.38; according to the Bortle Dark-Sky Scale this is bright enough to be seen even from city skies under ideal viewing conditions. Based upon parallax measurements, the distance to this star is around {{Convert|283|ly|pc|abbr=off|lk=on}}.

This is a giant star with a stellar classification of K4 III. It is a suspected variable star that apparently ranges in magnitude between 4.35 and 4.45. The measured angular diameter of this star is {{nowrap|3.55 ± 0.21 mas}}. At the estimated distance of Delta Ophiuchi, this yields a physical size of about 33 times the radius of the Sun. The outer atmosphere has an effective temperature of 3980 K, giving it the orange-hued glow of a cool, K-type star.

This star was a candidate member of the Ursa Major Moving Group based on the work of American astronomer Nancy Roman, but this membership is now in question.

References

{{reflist|refs=

{{citation | first=F. | last=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 | postscript=. |arxiv = 0708.1752 | s2cid=18759600 }}

{{citation | last1=McWilliam | first1=Andrew | title=High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances | journal=Astrophysical Journal Supplement Series | volume=74 | pages=1075–1128 |date=December 1990 | doi=10.1086/191527 | bibcode=1990ApJS...74.1075M | postscript=. | doi-access=free }}

{{citation | last1=Houk | first1=Nancy | title=Michigan catalogue of two-dimensional spectral types for the HD stars | volume=4 | publication-place=Ann Arbor | publisher=Dept. of Astronomy, University of Michigan | date=1978 | bibcode=1988mcts.book.....H | postscript=. }}

{{citation | last=Wilson | first=Ralph Elmer | date=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institution of Washington | location=Washington | bibcode=1953GCRV..C......0W | postscript=. }}

{{citation | last1=Jennens | first1=P. A. | last2=Helfer | first2=H. L. | title=A new photometric metal abundance and luminosity calibration for field G and K giants. | journal=Monthly Notices of the Royal Astronomical Society | volume=172 | pages=667–679 |date=September 1975 | issue=3 | bibcode=1975MNRAS.172..667J | postscript=. | doi=10.1093/mnras/172.3.667| doi-access=free }}

{{citation | last1=Richichi | first1=A. | last2=Percheron | first2=I. | last3=Khristoforova | first3=M. | title=CHARM2: An updated Catalog of High Angular Resolution Measurements | journal=Astronomy and Astrophysics | volume=431 | pages=773–777 |date=February 2005 | issue=2 | doi=10.1051/0004-6361:20042039 | bibcode=2005A&A...431..773R | postscript=. | doi-access=free }}

{{citation | first1=Kenneth R. | last1=Lang | title=Astrophysical formulae | volume=1 | series=Astronomy and astrophysics library | edition=3rd | publisher=Birkhäuser | date=2006 | isbn=3-540-29692-1 | url=https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41 | postscript=. }}. The radius (R_*) is given by:

: $\begin{align} 2\cdot R_*
& = \frac{(87\cdot 3.55\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\
& \approx 66\cdot R_{\bigodot}
\end{align}$

{{citation|title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |access-date=2012-01-16 |postscript=. |url-status=dead |archive-url=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=March 18, 2012 }}

{{citation | display-authors=1 | last1=Samus | first1=N. N. | last2=Durlevich | first2=O. V. | last3=Kazarovets | first3=E. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | last6=Zharova | first6=A .V. | title=NSV 14554 | work=General Catalog of Variable Stars |date=March 2012 | url=http://www.sai.msu.su/gcvs/cgi-bin/ident.cgi?cat=HD++&num=220704 | access-date=2012-07-12 | postscript=. }}

{{citation | last1=Chupina | first1=N. V. | last2=Reva | first2=V. G. | last3=Vereshchagin | first3=S. V. | title=Kinematic structure of the corona of the Ursa Major flow found using proper motions and radial velocities of single stars | journal=Astronomy and Astrophysics | volume=451 | issue=3 | pages=909–916 |date=June 2006 | doi=10.1051/0004-6361:20054009 | bibcode=2006A&A...451..909C | postscript=. | doi-access=free }} See table 7.

}}

External links

[http://aladin.u-strasbg.fr/AladinPreview?-c=23+26+02.7861-20+38+31.251&ident=NSV+14554&submit=Aladin+previewer Image 99 Aquarii]

Category:K-type giants

Category:Suspected variables

Category:Ursa Major moving group

Category:Aquarius (constellation)

Category:Bright Star Catalogue objects