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Slow irregular variable
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<h2 id="nomenclature">Nomenclature</h2> <p>Irregular variable stars were first given acronyms based on the letter "I": <i>Ia</i>, <i>Ib</i>. and <i>Ic</i>.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> These were later refined so that the I codes were used "nebular" or "rapidly irregular" variable stars such as T Tauri and Orion variables. The remaining irregular stars, cool slowly varying giants and supergiants of type Ib or Ic were reassigned to Lb and Lc.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> When the <a href="/facts/General_Catalogue_of_Variable_Stars/E0Q7I4bn">General Catalogue of Variable Stars</a> standardised its acronyms to be all uppercase, the codes LB and LC were used.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p> <h3>Type Lb</h3> <p><i>Slow irregular variables of late spectral types (<a href="/facts/Stellar_classification/dYrIuK9H">K</a>, <a href="/facts/Stellar_classification/dYrIuK9H">M</a>, <a href="/facts/Carbon_star/zK6vSgYn">C</a>, <a href="/facts/S-type_star/nTzSvMbH">S</a>); as a rule, they are giants</i><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p><p>The GCVS also claims to give this type to slow irregular red variables where the luminosity or spectral type is not known, although it also uses the type L for slow irregular red stars where the spectral type or luminosity is unclear. The K5 star CO Cygni is given as a representative example.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <h3>Type Lc</h3> <p><i>Irregular variable supergiants of late spectral types having amplitudes of about 1 mag in V</i><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>The M2 supergiant <a href="/facts/TZ_Cassiopeiae/uN4GIF4b">TZ Cassiopeiae</a> is given as a representative example.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h2 id="list">List</h2> <p class="note">This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by adding missing items with reliable sources.</p> List of Slow Irregular Variables<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><table><tbody><tr><th>Designation (name)</th><th>Constellation</th><th>Discovery</th><th><i><a href="/facts/Apparent_magnitude/7pCTF1Me">Apparent magnitude</a></i> (Maximum)<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a></th><th><i><a href="/facts/Apparent_magnitude/7pCTF1Me">Apparent magnitude</a></i> (Minimum)<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a></th><th><i>Range of magnitude</i></th><th>Spectral type</th><th>Subtype</th><th>Comment</th></tr><tr><td><a href="/facts/U_Antliae/cj7c114l">U Antliae</a></td><td><a href="/facts/Antlia/qNToMV1P">Antlia</a></td><td> </td><td>8m.1 (p)</td><td>9m.7 (p)</td><td>1.6</td><td>N:v</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/Beta_Pegasi/5x1ofNlC">Beta Pegasi</a></td><td><a href="/facts/Pegasus_(constellation)/DpwfGQuF">Pegasus</a></td><td><a href="/facts/Johann_Friedrich_Julius_Schmidt/N1bCM8WL">Schmidt</a>, 1847</td><td>2m.31</td><td>2m.74</td><td>0.43</td><td>M2.3 II-III</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/Epsilon_Pegasi/jo1a3BIl">Epsilon Pegasi</a> (Enif)</td><td><a href="/facts/Pegasus_(constellation)/DpwfGQuF">Pegasus</a></td><td></td><td>2m.37</td><td>2m.45</td><td>0.07</td><td>K2 Ib</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/TX_Piscium/nJt8J5my">TX Piscium</a></td><td><a href="/facts/Pisces_(constellation)/2neTVRCz">Pisces</a></td><td> </td><td>4m.79</td><td>5m.20</td><td>0.42</td><td>C5 III</td><td>Lb</td><td> </td></tr><tr><td>Alpha Scorpii (<a href="/facts/Antares/adRhtq7X">Antares</a>)</td><td><a href="/facts/Scorpius/ddxFGlK0">Scorpius</a></td><td> </td><td>0m.88</td><td>1m.16</td><td>0.28</td><td>M1.5 Iab-b</td><td>Lc</td><td> </td></tr><tr><td>Alpha Tauri (<a href="/facts/Aldebaran/PPa2xB93">Aldebaran</a>)</td><td><a href="/facts/Taurus_(constellation)/Vd3R88wb">Taurus</a></td><td> </td><td>0m.75</td><td>0m.95</td><td>0.20</td><td>K5 III</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/Mu_Geminorum/XMcXFpNr">Mu Geminorum</a></td><td><a href="/facts/Gemini_(constellation)/uTHx4pw9">Gemini</a></td><td> </td><td>2m.75</td><td>3m.02</td><td>0.28</td><td>M3 III</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/BE_Camelopardalis/PuGEd6jR">BE Camelopardalis</a></td><td><a href="/facts/Camelopardalis/7RN3GScR">Camelopardalis</a></td><td> </td><td>4m.35</td><td>4m.48</td><td>0.13</td><td>M2 II</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/Tau4_Eridani/D8T59mgn">Tau4 Eridani</a></td><td><a href="/facts/Eridanus_(constellation)/cvtlSUun">Eridanus</a></td><td> </td><td>3m.57</td><td>3m.72</td><td>0.15</td><td>M3 III</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/13_Bo%C3%B6tis/edyuQUNy">13 Boötis</a></td><td><a href="/facts/Bootes/B74JhFQm">Bootes</a></td><td> </td><td>5m.29</td><td>5m.38</td><td>0.09</td><td>M2 IIIab</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/Psi_Virginis/vGhWmsFc">Psi Virginis</a></td><td><a href="/facts/Virgo_(constellation)/4bcIqNfd">Virgo</a></td><td> </td><td>4m.73</td><td>4m.96</td><td>0.23</td><td>M3 III</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/HD_155035/3rcvLxSf">V854 Arae</a></td><td><a href="/facts/Ara_(constellation)/aD6hl2c6">Ara</a></td><td> </td><td>5m.84</td><td>5m.99</td><td>0.12</td><td>M1.5 III</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/62_Sagittarii/fRpoP7rH">62 Sagittarii</a></td><td><a href="/facts/Sagittarius_(constellation)/ljtU4DQ2">Sagittarius</a></td><td> </td><td>4m.45</td><td>4m.62</td><td>0.17</td><td>M4 III</td><td>Lb</td><td> </td></tr><tr><td><a href="/facts/CQ_Camelopardalis/BBtPGJMg">CQ Camelopardalis</a></td><td><a href="/facts/Camelopardalis/7RN3GScR">Camelopardalis</a></td><td> </td><td>5m.15</td><td>5m.27</td><td>0.12</td><td>M0 II</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/Pi_Aurigae/GDEBxpH9">Pi Aurigae</a></td><td><a href="/facts/Auriga_(constellation)/dDDxtEJx">Auriga</a></td><td> </td><td>4m.24</td><td>4m.34</td><td>0.10</td><td>M3.5 II</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/NO_Aurigae/twTnRn2F">NO Aurigae</a></td><td><a href="/facts/Auriga_(constellation)/dDDxtEJx">Auriga</a></td><td> </td><td>6m.06</td><td>6m.44</td><td>0.58</td><td>M2 Iab</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/Omicron1_Canis_Majoris/qX35CWxp">Omicron1 Canis Majoris</a></td><td><a href="/facts/Canis_Major/mqRyjJoM">Canis Major</a></td><td> </td><td>3m.78</td><td>3m.99</td><td>0.21</td><td>M2.5 Iab</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/Sigma_Canis_Majoris/WT6It8jb">Sigma Canis Majoris</a></td><td><a href="/facts/Canis_Major/mqRyjJoM">Canis Major</a></td><td> </td><td>3m.43</td><td>3m.51</td><td>0.08</td><td>M1.5 Iab</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/NS_Puppis/zjKU4kk7">NS Puppis</a></td><td><a href="/facts/Puppis/sHlCP1ek">Puppis</a></td><td> </td><td>4m.4</td><td>4m.5</td><td>0.1</td><td>K3 Ib</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/Lambda_Velorum/LzAB3cnc">Lambda Velorum</a></td><td><a href="/facts/Vela_(constellation)/sRxGnXAE">Vela</a></td><td> </td><td>2m.14</td><td>2m.30</td><td>0.16</td><td>K4 Ib-IIa</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/V337_Carinae/15uoC19N">V337 Carinae</a></td><td><a href="/facts/Carina_(constellation)/WmAhubMs">Carina</a></td><td> </td><td>3m.36</td><td>3m.44</td><td>0.08</td><td>K3 II</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/GZ_Velorum/wS1t4udW">GZ Velorum</a></td><td><a href="/facts/Vela_(constellation)/sRxGnXAE">Vela</a></td><td> </td><td>3m.43</td><td>3m.81</td><td>0.38</td><td>K3 II</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/RX_Telescopii/cMWWx7gD">RX Telescopii</a></td><td><a href="/facts/Telescopium/HMTHvEYo">Telescopium</a></td><td> </td><td>6m.6</td><td>7m.4</td><td>0.8</td><td>M3 Iab</td><td>Lc</td><td> </td></tr><tr><td><a href="/facts/HD_77887/NAatyhdl">45 G. Volantis</a></td><td><a href="/facts/Volans/HFP7Uf9l">Volans</a></td><td></td><td>5m.89</td><td>5m.90</td><td>0.01</td><td>M1III</td><td>Lb</td><td></td></tr><tr><td><a href="/facts/AF_Columbae/KF5nUdPd">AF Columbae</a></td><td><a href="/facts/Columba_(constellation)/Xwbbd2jB">Columba</a></td><td>Perryman et al., 1997</td><td>5m.60</td><td>5m.71</td><td>0.11</td><td>M2 II/III</td><td>Lb</td><td></td></tr></tbody></table> <h2 id="other-irregular-variables">Other irregular variables</h2> <p>There are a number of other types of variable stars lacking clearly detectable periods, and which are sometimes referred to as <a href="/facts/Irregular_variable/xWkauC0E">irregular variables</a>:<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <ul><li><a href="/facts/%CE%93_Cassiopeiae_variable/KDNqEC65">γ Cassiopeiae variables</a>, eruptive <a href="/facts/Shell_star/KDNqEC65">shell stars</a></li> <li><a href="/facts/Orion_variable/lTxWyBCf">Orion variables</a>, pre-main-sequence stars, including <a href="/facts/T_Tauri_star/vX5WL56u">T Tauri stars</a> and <a href="/facts/YY_Orionis_star/lTxWyBCf">YY Orionis stars</a></li> <li>Rapid irregular variables, possibly similar to Orion variables with shorter period</li> <li>Poorly-defined irregular variable stars, of unknown type</li></ul> <p>In addition, many types of <a href="/facts/Eruptive_variable/Ac8mp2gy">eruptive</a> or <a href="/facts/Cataclysmic_variable/QgRCfaYj">cataclysmic variable</a> are highly unpredictable.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <h2 id="external-links">External links</h2> <ul><li><a href="https://www.assa.org.au/sig/variables/classifications">Classifying variable stars</a> - Astronomical Society of South Australia</li> <li><a href="http://www.britastro.org/vss/holland.pdf">Why observe variable stars</a> - British Astronomical Association</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Kholopov, P. N. (1959). "A Revised List of T-Associations and Their Members". Soviet Astronomy. 3: 291. Bibcode:1959SvA.....3..291K. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Mayall, Margaret W. (1964). "Variable Star Notes- from the XII General Assembly, I.A.U.; 043274 X Camelopardalis". Journal of the Royal Astronomical Society of Canada. 58: 283. Bibcode:1964JRASC..58..283M. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"GCVS Variability Types". Retrieved 2016-09-04. <a href="http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt" target="_blank">http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"GCVS Variability Types". Retrieved 2016-09-04. <a href="http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt" target="_blank">http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"GCVS Variability Types". Retrieved 2016-09-04. <a href="http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt" target="_blank">http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"GCVS Variability Types". Retrieved 2016-09-04. <a href="http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt" target="_blank">http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"GCVS Variability Types". Retrieved 2016-09-04. <a href="http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt" target="_blank">http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>(visual magnitude, unless marked (B) (= blue) or (p) (= photographic)) <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>(visual magnitude, unless marked (B) (= blue) or (p) (= photographic)) <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> </ol>