{{Short description|Star in the constellation Boötes}} {{Starbox begin | name=HD 123657<br/>(BY Boötis) }} {{Starbox image | image= {{Location mark |image=Boötes constellation map.svg |float=center |alt= |label= |position=right |width=240 |mark=Red circle.svg |mark_width=10 |mark_link=BY Boötis |x=715|y=284 }} |caption=Location of BY Boö (circled) }} {{Starbox observe | epoch=J2000 | constell=[[Boötes]] | ra={{RA|14|07|55.755}}<ref name=dr3/> | dec={{DEC|+43|51|16.03}}<ref name=dr3/> | appmag_v={{Val|4.98|-|5.33}}<ref name=gcvs/><ref name=AAVSO/> }} {{Starbox character | type = [[asymptotic giant branch|AGB]]<ref name=ah2024/> | class=M4.5III<ref name=alvarez/> | r-i = 1.66<ref name=ducati/> | b-v = 1.58<ref name=ducati/> | u-b = 1.66<ref name=ducati/> | variable=[[Slow irregular variable|LB]]<ref name=alvarez/> }} {{Starbox astrometry | radial_v={{Val|-36.24}}<ref name=Famaey2005/> | prop_mo_ra= +11.443 | prop_mo_dec={{Val|-30.812}} | pm_footnote = <ref name=dr3/> | parallax=6.0110 | p_error=0.1554 | parallax_footnote=<ref name=dr3/> | absmag_v=−0.90<ref name=park/> }} {{Starbox detail | mass=3.96<ref name=charbonnel2020/> | radius={{Val|131.7|3.4|3.5}}<ref name=Baines2025/> | luminosity={{Val|2100|300|fmt=commas}}<ref name=Alonso-Hernández2026/> | temperature={{Val|3400|100|120|fmt=commas}}<ref name=Alonso-Hernández2026/> | metal_fe=−0.03<ref name=marrese/> | gravity= 0.66<ref name=coelho2020/> | rotation= | age= }} {{Starbox catalog | names=BY Boötis, [[Henry Draper Catalogue|HD]] 123657, [[Hipparcos Catalogue|HIP]] 69038, [[Bright Star Catalogue|HR]] 5299, [[Guide Star Catalog|GSC]] 03040-00969, [[Tycho Catalogue|TYC]] 3040-969-1, [[Bonner Durchmusterung|BD]]+44°2325, [[IRAS]] 14059+4405, [[Two-Micron Sky Survey|IRC]] +40253, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 44901 }} {{Starbox reference | Simbad=HD+123657 | ARICNS = }} {{Starbox end}}
'''HD 123657''' ('''BY Boötis''') is a star in the northern constellation of [[Boötes]], near the end of the handle of the [[Big Dipper]]. It is a fifth-magnitude star, and can be spotted to the [[unaided eye]] in sufficiently [[dark-sky preserve|dark skies]], far from [[light pollution]]. Based on [[stellar parallax]] measurements, it is about 540 [[light-year]]s distant.
[[File:BYBooLightCurve.png|thumb|left|A [[light curve]] for BY Boötis, plotted from ''[[Hipparcos]]'' data<ref name=HipDataAccess/>]] This is a [[slow irregular variable]] with an apparent magnitude varying between 4.98 and 5.33.<ref name=gcvs/><ref name=AAVSO/> The variability of the brightness of HD 123657 was announced by [[Joel Stebbins]] and [[Charles Morse Huffer]] in 1928, based on observations made at [[Washburn Observatory]].<ref name="Stebbins1928"/> The star was given its [[variable star designation]], BY Boötis, in 1973.<ref name="Kukarkin1973"/>
HD 123657 has a [[spectral type|spectral classification]] of M4.5III,<ref name=alvarez/> placing it as a cool [[red giant]] that exhausted its hydrogen supply. It has expanded to over 132 times the [[size of the Sun]],<ref name=Baines2025/> now radiating 2,100 times [[solar luminosity|its luminosity]] at a cool [[photosphere]] that has an [[effective temperature]] of {{Val|3400|ul=K|fmt=commas}}.<ref name=Alonso-Hernández2026/> {{clear left}}
== References == <references> <ref name=dr3>{{cite Gaia DR3|1505343882144388864}}</ref>
<ref name=ah2024>{{cite journal |bibcode=2024A&A...684A..77A |title=CO emission survey of asymptotic giant branch stars with ultraviolet excesses |last1=Alonso-Hernández |first1=J. |last2=Sánchez Contreras |first2=C. |last3=Sahai |first3=R. |journal=Astronomy and Astrophysics |date=2024 |volume=684 |pages=A77 |doi=10.1051/0004-6361/202347317 |arxiv=2401.08546 }}</ref>
<ref name=charbonnel2020>{{cite journal |bibcode=2020A&A...633A..34C |title=Lithium in red giant stars: Constraining non-standard mixing with large surveys in the Gaia era |last1=Charbonnel |first1=C. |last2=Lagarde |first2=N. |last3=Jasniewicz |first3=G. |last4=North |first4=P. L. |last5=Shetrone |first5=M. |last6=Krugler Hollek |first6=J. |last7=Smith |first7=V. V. |last8=Smiljanic |first8=R. |last9=Palacios |first9=A. |last10=Ottoni |first10=G. |journal=Astronomy and Astrophysics |date=2020 |volume=633 |pages=A34 |doi=10.1051/0004-6361/201936360 |arxiv=1910.12732 }}</ref>
<ref name=coelho2020>{{cite journal |bibcode=2020MNRAS.491.2025C |title=To use or not to use synthetic stellar spectra in population synthesis models? |last1=Coelho |first1=Paula R. T. |last2=Bruzual |first2=Gustavo |last3=Charlot |first3=Stéphane |journal=Monthly Notices of the Royal Astronomical Society |date=2020 |volume=491 |issue=2 |page=2025 |doi=10.1093/mnras/stz3023 |doi-access=free |arxiv=1910.11902 }}</ref>
<ref name="Stebbins1928">{{cite journal |last1=Stebbins |first1=Joel |last2=Huffer |first2=C. M. |title=The Constancy of the Light of Red Stars |journal=Publications of the Washburn Observatory |date=1928 |volume=15 |pages=137–174 |bibcode=1928PWasO..15..137S }}</ref>
<ref name=HipDataAccess>{{cite web |title=Hipparcos Tools Interactive Data Access |url=https://www.cosmos.esa.int/web/hipparcos/interactive-data-access |website=Hipparcos |publisher=ESA |access-date=8 December 2021}}</ref>
<ref name="Kukarkin1973">{{cite journal |last1=Kukarkin |first1=B. V. |last2=Kholopov |first2=P. N. |last3=Kukarkina |first3=N. P. |last4=Perova |first4=N. B. |title=59th Name-List of Variable Stars |journal=Information Bulletin on Variable Stars |date=October 1973 |volume=834 |pages=1–22 |bibcode=1973IBVS..834....1K |url=https://ibvs.konkoly.hu/pub/ibvs/0801/0834.pdf |access-date=4 December 2024}}</ref>
<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|year=2002}}</ref>
<ref name=Baines2025>{{cite journal |last=Baines |first=Ellyn K. |last2=Clark |first2=James H. |last3=Kingsley |first3=Bradley I. |last4=Schmitt |first4=Henrique R. |last5=Stone |first5=Jordan M. |date=2025-05-07 |title=Vintage NPOI: New and Updated Angular Diameters for 145 Stars |journal=The Astronomical Journal |language=en |volume=169 |issue=6 |pages=293 |doi=10.3847/1538-3881/adc930 |doi-access=free |arxiv=2506.02912 |issn=1538-3881}}</ref>
<ref name=AAVSO>{{Cite web |title=VSX : Detail for BY Boo |url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=4405 |access-date=2025-03-11 |website=www.aavso.org}}</ref>
<ref name=alvarez>{{cite journal|doi=10.1051/0004-6361:20011261|title=Envelope tomography of long-period variable stars|journal=Astronomy and Astrophysics|volume=379|pages=305–322|year=2001|last1=Alvarez|first1=R.|last2=Jorissen|first2=A.|last3=Plez|first3=B.|last4=Gillet|first4=D.|last5=Fokin|first5=A.|last6=Dedecker|first6=M.|bibcode=2001A&A...379..305A|arxiv = astro-ph/0109259 |s2cid=15502307}}</ref>
<ref name=park>{{cite journal|bibcode=2013AJ....146...73P|arxiv=1307.0592|title=Wilson-Bappu Effect: Extended to Surface Gravity|journal=The Astronomical Journal|volume=146|issue=4|pages=73|last1=Park|first1=Sunkyung|last2=Kang|first2=Wonseok|last3=Lee|first3=Jeong-Eun|last4=Lee|first4=Sang-Gak|year=2013|doi=10.1088/0004-6256/146/4/73|s2cid=119187733}}</ref>
<ref name=Alonso-Hernández2026>{{Cite journal |last=Alonso-Hernández |first=J. |last2=Sánchez Contreras |first2=C. |last3=Sahai |first3=R. |last4=Sanz-Forcada |first4=J. |date=2026-04-13 |title=The dusty envelopes of asymptotic giant branch stars with ultraviolet excesses |journal=Astronomy & Astrophysics |doi=10.1051/0004-6361/202659537 |issn=0004-6361|doi-access=free |arxiv=2603.19815 }}</ref>
<ref name=marrese>{{cite journal|bibcode=2003A&A...406..995M|title=High resolution spectroscopy over lambda lambda 8500-8750 Å for GAIA. IV. Extending the cool MK stars sample|journal=Astronomy and Astrophysics|volume=406|issue=3|pages=995|last1=Marrese|first1=P. M.|last2=Boschi|first2=F.|last3=Munari|first3=U.|year=2003|doi=10.1051/0004-6361:20030647|doi-access=free}}</ref>
<ref name=Famaey2005>{{cite journal|bibcode=2005A&A...430..165F|title=Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters|journal=Astronomy and Astrophysics|volume=430|pages=165|last1=Famaey|first1=B.|last2=Jorissen|first2=A.|last3=Luri|first3=X.|last4=Mayor|first4=M.|last5=Udry|first5=S.|last6=Dejonghe|first6=H.|last7=Turon|first7=C.|year=2005|doi=10.1051/0004-6361:20041272|arxiv = astro-ph/0409579 |s2cid=17804304}}</ref>
<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref> </references>
{{Stars of Boötes}}
[[Category:Boötes]] [[Category:Henry Draper Catalogue objects|123657]] [[Category:Hipparcos objects|069038]] [[Category:M-type giants]] [[Category:Bright Star Catalogue objects|5299]] [[Category:Objects with variable star designations|Boötis, BY]] [[Category:Slow irregular variables]] [[Category:Durchmusterung objects]]