LQ Hydrae

{{Short description|Star in the constellation Hydra}} {{Starbox begin}} {{Starbox image | image = [[Image:LQHyaLightCurve.png|250px]] | caption = A [[Photometric_system#Photometric_letters|visual band]] [[light curve]] for LQ Hydrae. The main plot (adapted from Berdyugina ''et al.''<ref name=Berdyugina_et_al_2002/>) shows the long-term variation, and the inset plot (adapted from Kiraga<ref name="Kiraga"/>) shows the periodic variation. }} {{Starbox observe | epoch = J2000.0 | constell = [[Hydra (constellation)|Hydra]]<ref name=Anderson_Francis_2012/> | ra = {{RA|09|32|25.568}}<ref name=GaiaDR3/> | dec = {{DEC|−11|11|04.69}}<ref name=GaiaDR3/> | appmag_v = 7.79 to 7.86<ref name=Samus_et_al_2017/> }} {{Starbox character | type = Main sequence | class = K1Vp<ref name=Houk_Swift_1999/> | b-v = 0.933{{±|0.021}}<ref name=Anderson_Francis_2012/> | u-b = | variable = [[BY Draconis variable|BY Dra]]<ref name=Samus_et_al_2017/> }} {{Starbox astrometry | radial_v = 7.58{{±|0.27}}<ref name=Halbwachs_et_al_2018/> | prop_mo_ra = −248.040 | prop_mo_dec = 34.277 | pm_footnote = <ref name=GaiaDR3/> | parallax = 54.7362 | p_error = 0.0244 | parallax_footnote = <ref name=GaiaDR3/> | absmag_v = 6.47<ref name=Houk_Swift_1999/> }} {{Starbox detail | mass = 0.81<ref name=Luck2018/> | radius = 1.0<ref name=Strassmeier2009/> | luminosity = 0.282{{±|0.001}}<ref name=GaiaDR3/> | gravity = 4.57<ref name=Luck2018/> | temperature = 4,812{{±|39}}<ref name=Luck2018/> | metal_fe = 0.32<ref name=Luck2018/> | rotation = 1.601<ref name=Strassmeier2009/> [[day|d]] | rotational_velocity = 25{{±|2}}<ref name=Jetsu1993/> | age_myr = Under 75<ref name=Montes_et_al_1999/> }} {{Starbox catalog | names = {{odlist | V=LQ Hya | BD=−10 2857 | GC=13168 | GJ=355 | HD=82558 | HIP=46816 | LTT=3510 | SAO=155272 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = LQ+Hya }} {{Starbox end}}

'''LQ Hydrae''' is a single<ref name=Fekel_et_al_1986b/> [[variable star]] in the [[celestial equator|equatorial]] [[constellation]] of [[Hydra (constellation)|Hydra]]. It is sometimes identified as '''Gl 355''' from the [[Gliese Catalogue of Nearby Stars|Gliese Catalogue]]; ''LQ Hydrae'' is the [[variable star designation]], which is abbreviated LQ Hya.<ref name=Covino_et_al_2001/> The brightness of the star ranges from an [[apparent visual magnitude]] of 7.79 down to 7.86,<ref name=Samus_et_al_2017/> which is too faint to be readily visible to the naked eye. Based on [[stellar parallax|parallax]] measurements, this star is located at a distance of 59.6 [[light year]]s from the [[Sun]]. It is drifting further away with a [[radial velocity]] of 7.6 km/s.<ref name=Halbwachs_et_al_2018/>

During a 1981 survey of southern stars, [[William P. Bidelman|W. P. Bidelman]] found the [[H and K lines]] of ionized calcium for LQ Hya were filled in with [[Emission-line|emission]]. ([[Wulff-Dieter Heintz|W. D. Heintz]] independently made the same observation.) In 1986, [[Francis C. Fekel|F. C. Fekel]] and associates determined this is a young, rapidly rotating [[BY Draconis variable|BY Draconis-type variable]].<ref name=Fekel_et_al_1986b/><ref name=Fekel_et_al_1986a/> A decade of photometry was used to determine a [[rotation period]] of 1.601136{{±|0.000013}} days (1 day, 14 hours, and 24 minutes) The [[star spot]]s on the surface showed significant evolution over time scales of a few months. Variations in rotational modulation of surface activity suggested the star is undergoing [[differential rotation]].<ref name=Jetsu1993/>

The high [[lithium]] abundance and rapid rotation of this star indicate it is a [[zero age main sequence]] star, or possibly even a [[pre-main sequence star]].<ref name=Covino_et_al_2001/> A strong [[Flare star|flare]] event was observed on December 22, 1993, with an estimated energy release of {{val|5.7|e=33|u=erg|p=~}}.<ref name=Montes_et_al_1999/> Additional flares were detected thereafter, with [[ROSAT]] [[Astrophysical X-ray source|X-ray]] data from 1992 showing a strong flare during that time period.<ref name=Covino_et_al_2001/> Observations from December 2000 and 2001 showed that the [[stellar magnetic field|magnetic field]] of the star is dramatically changing its topology on a time frame of a year or less.<ref name=McIfor_et_al_2004/>

The [[stellar classification]] of LQ Hya is K1Vp,<ref name=Houk_Swift_1999/> indicating it is a [[K-type main-sequence star]] with some peculiar features in the spectrum. In some respects it is considered an [[solar analog|analog of a young Sun]] around the age of 60 million years.<ref name=Berdyugina_et_al_2002/> It shows strong emission of ultraviolet and has been detected in the X-ray band, showing an X-ray emission of {{val|8.8|e=29|u=erg/s}} and indicating high chromospheric activity levels.<ref name=Covino_et_al_2001/> The star shows dual magnetic activity cycles with period of 6.8 and 11.4 years,<ref name=Covino_et_al_2001/> which are somewhat comparable to the [[solar cycle]] in the Sun.

== References == <references> <ref name=SIMBAD>{{cite simbad | title=LQ Hya | access-date=2022-02-23 | postscript=. | mode=cs2 }}</ref>

<ref name=Samus_et_al_2017>{{citation | postscript=. | title=General catalogue of variable stars | version=GCVS 5.1 | last1=Samus' | first1=N. N | last2=Kazarovets | first2=E. V | last3=Durlevich | first3=O. V | last4=Kireeva | first4=N. N | last5=Pastukhova | first5=E. N | journal=Astronomy Reports | display-authors=1 | volume=61 | issue=1 | pages=80 | year=2017 | bibcode=2017ARep...61...80S | s2cid=125853869 | doi=10.1134/S1063772917010085 }}</ref>

<ref name=Houk_Swift_1999>{{citation | last1=Houk | first1=N. | last2=Swift | first2=C. | title=Michigan catalogue of two-dimensional spectral types for the HD Stars | journal=Michigan Spectral Survey | volume=5 | year=1999 | postscript=. | bibcode=1999MSS...C05....0H }}</ref>

<ref name=Halbwachs_et_al_2018>{{citation | postscript=. | title=Multiplicity among solar-type stars. IV. The CORAVEL radial velocities and the spectroscopic orbits of nearby K dwarfs | display-authors=1 | last1=Halbwachs | first1=J. -L. | last2=Mayor | first2=M. | last3=Udry | first3=S. | last4=Fekel | first4=F. C. | last5=Hartkopf | first5=W. I. | last6=Levato | first6=H. | last7=Morrell | first7=N. I. | last8=Torres | first8=G. | last9=Udry | first9=S. | journal=Astronomy and Astrophysics | volume=619 | pages=A81 | year=2018 | bibcode=2018A&A...619A..81H | arxiv=1808.04605 | doi=10.1051/0004-6361/201833377 | s2cid=119437322 }}</ref>

<ref name=Strassmeier2009>{{citation | postscript=. | title=Starspots | last=Strassmeier | first=Klaus G. | journal=The Astronomy and Astrophysics Review | volume=17 | issue=3 | pages=251–308 | date=September 2009 | doi=10.1007/s00159-009-0020-6 | bibcode=2009A&ARv..17..251S | doi-access=free }}</ref>

<ref name=Luck2018>{{citation | title=Abundances in the Local Region. III. Southern F, G, and K Dwarfs | last=Luck | first=R. Earle | postscript=. | journal=The Astronomical Journal | volume=155 | issue=3 | id=111 | pages=31 | date=March 2018 | doi=10.3847/1538-3881/aaa9b5 | bibcode=2018AJ....155..111L | s2cid=125765376 | doi-access=free }}</ref>

<ref name=Fekel_et_al_1986a>{{citation | postscript=. | title=A Survey of Chromospherically Active Stars | display-authors=1 | last1=Fekel | first1=F. C. | last2=Moffett | first2=T. J. | last3=Henry | first3=G. W. | journal=Astrophysical Journal Supplement | volume=60 | page=551 | date=February 1986 | doi=10.1086/191097 | bibcode=1986ApJS...60..551F }}</ref>

<ref name="Kiraga">{{cite journal | last1=Kiraga |first1=M. | title=ASAS Photometry of ROSAT Sources. I. Periodic Variable Stars Coincident with Bright Sources from the ROSAT All Sky Survey | journal=Acta Astronomica |date=March 2012 |volume=62 |issue=1 |pages=67–95 |arxiv=1204.3825 |bibcode=2012AcA....62...67K |url=http://acta.astrouw.edu.pl/Vol62/n1/pdf/pap_62_1_4.pdf |access-date=23 June 2022}}</ref>

<ref name=Fekel_et_al_1986b>{{citation | postscript=. | title=Chromospherically active stars. II. HD 82558, a young single BY Draconis variable | display-authors=1 | last1=Fekel | first1=F. C. | last2=Bopp | first2=B. W. | last3=Africano | first3=J. L. | last4=Goodrich | first4=B. D. | last5=Palmer | first5=L. H. | last6=Quingley | first6=R. | last7=Simon | first7=T. | journal=Astronomical Journal | volume=92 | pages=1150–1154 | date=November 1986 | doi=10.1086/114246 | bibcode=1986AJ.....92.1150F }}</ref>

<ref name=Jetsu1993>{{citation | postscript=. | title=A decade of photometry of LQ Hydrae | last=Jetsu | first=L. | journal=Astronomy and Astrophysics | volume=276 | pages=345–352 | date=September 1993 | bibcode=1993A&A...276..345J }}</ref>

<ref name=Montes_et_al_1999>{{citation | postscript=. | title=Optical and ultraviolet observations of a strong flare in the young, single K2 dwarf LQ Hya | last1=Montes | first1=D. | last2=Saar | first2=S. H. | last3=Collier Cameron | first3=A. | last4=Unruh | first4=Y. C. | display-authors=1 | journal=Monthly Notices of the Royal Astronomical Society | volume=305 | issue=1 | pages=45–60 | date=May 1999 | doi=10.1046/j.1365-8711.1999.02373.x | doi-access=free | arxiv=astro-ph/9811452 | bibcode=1999MNRAS.305...45M | s2cid=10033733 }}</ref>

<ref name=Covino_et_al_2001>{{citation | postscript=. | title=Quiescent and flare analysis for the chromospherically active star Gl 355 (LQ Hya) | last1=Covino | first1=S. | last2=Panzera | first2=M. R. | last3=Tagliaferri | first3=G. | last4=Pallavicini | first4=R. | display-authors=1 | journal=Astronomy and Astrophysics | volume=371 | pages=973–985 | date=June 2001 | issue=3 | doi=10.1051/0004-6361:20010454 | arxiv=astro-ph/0103473 | bibcode=2001A&A...371..973C | s2cid=119518367 }}</ref>

<ref name=McIfor_et_al_2004>{{citation | postscript=. | title=The changing corona of LQ Hya | display-authors=1 | last1=McIvor | first1=T. | last2=Jardine | first2=M. | last3=Collier Cameron | first3=A. | last4=Wood | first4=K. | last5=Donati | first5=J. -F. | journal=Monthly Notices of the Royal Astronomical Society | volume=355 | issue=4 | pages=1066–1072 | date=December 2004 | doi=10.1111/j.1365-2966.2004.08391.x | doi-access=free | bibcode=2004MNRAS.355.1066M | s2cid=120518212 }}</ref>

<ref name=Berdyugina_et_al_2002>{{citation | postscript=. | title=Magnetic activity in the young solar analog LQ Hydrae. I. Active longitudes and cycles | display-authors=1 | last1=Berdyugina | first1=S. V. | last2=Pelt | first2=J. | last3=Tuominen | first3=I. | journal=Astronomy and Astrophysics | volume=394 | pages=505–515 | date=November 2002 | issue=2 | doi=10.1051/0004-6361:20021179 | bibcode=2002A&A...394..505B | doi-access=free }}</ref> </references>

==Further reading== {{Div col|small=yes}} *{{citation | postscript=. | title=Spot evolution on LQ Hya from 2006-2017: temperature maps based on SOFIN and FIES data | display-authors=1 | last1=Cole-Kodikara | first1=Elizabeth M. | last2=Käpylä | first2=Maarit J. | last3=Lehtinen | first3=Jyri J. | last4=Hackman | first4=Thomas | last5=Ilyin | first5=Ilya V. | last6=Piskunov | first6=Nikolai | last7=Kochukhov | first7=Oleg | journal=Astronomy & Astrophysics | volume=629 | id=A120 | pages=9 | date=September 2019 | doi=10.1051/0004-6361/201935729 | arxiv=1904.08713 | bibcode=2019A&A...629A.120C | s2cid=121348666 }} *{{citation | postscript=. | title=Doppler imaging of LQ Hydrae for 1998-2002 | last1=Cole | first1=E. M. | last2=Hackman | first2=T. | last3=Käpylä | first3=M. J. | last4=Ilyin | first4=I. | last5=Kochukhov | first5=O. | last6=Piskunov | first6=N. | display-authors=1 | journal=Astronomy & Astrophysics | volume=581 | id=A69 | pages=9 | date=September 2015 | doi=10.1051/0004-6361/201425440 | arxiv=1504.03673 | bibcode=2015A&A...581A..69C | s2cid=118155166 }} *{{citation | postscript=. | title=Chromospheric activity on late-type star LQ Hya | display-authors=1 | last1=Zhang | first1=Liyun | last2=Pi | first2=Qingfeng | last3=Zhu | first3=Zhongzhong | last4=Zhang | first4=Xiliang | last5=Li | first5=Zhongmu | journal=New Astronomy | volume=32 | pages=1–5 | date=October 2014 | doi=10.1016/j.newast.2014.02.010 | bibcode=2014NewA...32....1Z }} *{{citation | postscript=. | title=Chromospheric Activity and Rotational Modulation on the Young, Single K2 Dwarf LQ Hya | last1=Cao | first1=Dong-tao | last2=Gu | first2=Sheng-hong | display-authors=1 | journal=The Astronomical Journal | volume=147 | issue=2 | id=38 | pages=10 | date=February 2014 | doi=10.1088/0004-6256/147/2/38 | bibcode=2014AJ....147...38C | s2cid=120310890 | doi-access=free }} *{{citation | postscript=. | title=Differential rotation of LQ Hya and IL Hya from Doppler imaging | last1=Kõvári | first1=Zs. | last2=Weber | first2=M. | work=Proceedings of the British-Hungarian N+N Workshop for Young Researchers On Computer processing and use of satellite data in astronomy and astrophysics and 3rd Workshop of Young Researchers in Astronomy & Astrophysics; Hungary, 3-7 February 2004 | publisher=Publications of the Astronomy Department of the Eötvös University (PADEU) | editor1-first=E. | editor1-last=Forgács-Dajka | editor2-first=K. | editor2-last=Petrovay | editor3-first=R. | editor3-last=Erdélyi | volume=14 | pages=221–232 | date=June 2004 | bibcode=2004PADEU..14..221K }} *{{citation | postscript=. | title=Butterfly Diagram for Starspots on LQ Hya | last1=Livshits | first1=M. A. | last2=Alekseev | first2=I. Yu. | last3=Katsova | first3=M. M. | journal=Astronomy Reports | volume=47 | issue=7 | pages=562–572 | date=July 2003 | doi=10.1134/1.1592835 | bibcode=2003ARep...47..562L | s2cid=122361382 }} *{{citation | postscript=. | title=Spots and Active Regions on Emission Stars. III. LQ Hya | last1=Alekseev | first1=I. Yu. | last2=Kozlova | first2=O. V. | journal=Astrophysics (English Translation of Astrofizika) | volume=46 | issue=1 | pages=28–45 | date=January 2003 | doi=10.1023/A:1022959419060 | bibcode=2003Ap.....46...28A | s2cid=116908588 }} *{{citation | postscript=. | title=Magnetic cycles of HR 1099 and LQ Hydrae | last=Donati | first=J. -F. | journal=Monthly Notices of the Royal Astronomical Society | volume=302 | issue=3 | pages=457–481 | date=January 1999 | doi=10.1046/j.1365-8711.1999.02096.x | bibcode=1999MNRAS.302..457D | doi-access=free }} *{{citation | postscript=. | title=Multiple Epoch Magnetic Surface Images of LQ Hya | display-authors=1 | last1=Saar | first1=S. H. | last2=Piskunov | first2=N. E. | last3=Tuominen | first3=I. | work=The Eighth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun | editor-first=J.-P. | editor-last=Caillault | series=Astronomical Society of the Pacific Conference Series | volume=64 | pages=661–663 | date=1994 | bibcode=1994ASPC...64..661S }} *{{citation | postscript=. | title=Surface features of the lower atmosphere of HD 82558 (=LQ Hydrae) | display-authors=1 | last1=Strassmeier | first1=K. G. | last2=Rice | first2=J. B. | last3=Wehlau | first3=W. H. | last4=Hill | first4=G. M. | last5=Matthews | first5=J. M. | journal=Astronomy and Astrophysics | volume=268 | pages=671–684 | date=February 1993 | bibcode=1993A&A...268..671S }} *{{citation | postscript=. | title=Magnetic Surface Images of the BY DRA Star HD 82558 | display-authors=1 | last1=Saar | first1=S. H. | last2=Piskunov | first2=N. E. | last3=Tuominen | first3=I. | work=The Seventh Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun | editor1-first=M. S. | editor1-last=Giampapa | editor2-first=J. A. | editor2-last=Bookbinder | series=Astronomical Society of the Pacific Conference Series | volume=26 | pages=255–258 | date=1992 | bibcode=1992ASPC...26..255S }} {{Div col end}}

[[Category:K-type main-sequence stars]] [[Category:BY Draconis variables]] [[Category:Solar analogs]]  [[Category:Hydra (constellation)]] [[Category:Durchmusterung objects|BD-10 2857]] [[Category:Henry Draper Catalogue objects|082558]] [[Category:Hipparcos objects|046816]] [[Category:Objects with variable star designations|Hydrae, LQ]] [[Category:Gliese and GJ objects|0355]]