NGC 6205 / C1639+365 / Messier 13 (Updated January 2024) RA: 16:41:41.24 +36:27:35.5 (J2000) ============================================================ Bytes Format Explanation 1-8 A8 Star ID 10-32 A11,1x,A11 Position 34-35 A2 Units for position R0 denotes RA, DEC in the J2000 coordinates R5 denotes RA, DEC in the 1950 coordinates XA denotes X, Y in arcseconds XP denotes X, Y in pixels 37-44 F8.4 Period (days) 46-51 F6.3 Mean magnitude (or maximum magnitude if "max" is indicated in the remarks column) 53-57 F5.3 Light amplitude (range of variability) 59 A1 Colour for mean magnitude and amplitude e.g. B, V, R, I, J, K or P (for photographic). 61-65 A5 Type of variable (draft 2006 GCVS classifications) CST denotes non variable stars previously designated as variables 67-80 A19 Notes and Remarks (f denotes field star) "--" or "----" indicates no data available ========================================================================= ID Position Period ampl C Type Notes/ RA/X Dec/Y Units Remarks ========================================================================= 1 16:41:46.45 +36:27:27.7 R0 1.4590 14.050 1.034 V CW OsC 2 16:41:35.88 +36:27:48.3 R0 5.1108 12.977 0.875 V CW OsC 3 16:41:29.75 +36:28:07.2 R0 ---- -- -- CST 4 16:41:36.17 +36:28:51.5 R0 ---- -- -- CST 5 16:41:46.35 +36:27:39.9 R0 0.3818 14.767 0.425 V RR1 6 16:41:47.95 +36:29:09.6 R0 2.1129 14.044 0.584 V CW OsC 7 16:41:37.10 +36:26:28.8 R0 0.3127 14.925 0.305 V RR1 8 16:41:32.64 +36:28:02.0 R0 0.7503 14.850 0.836 V RR0 9 16:41:46.24 +36:27:37.8 R0 0.3928 14.819 0.434 V RR1 10 16:41:39.96 +36:26:41.3 R0 ---- -- -- CST Note 11 16:41:36.61 +36:26:35.3 R0 92.0 11.91 0.30 V SR Os 12 16:41:31.54 +36:28:44.1 R0 ---- -- -- CST 13 16:41:36.65 +36:27:20.8 R0 ---- -- -- CST 14 16:41:40.52 +36:31:20.0 R0 ---- -- -- CST Note 15 16:41:46.98 +36:25:57.3 R0 ---- 12.12 0.10 V SR Os;P=30: 16 16:42:01.11 +36:33:45.3 R0 ---- -- -- CST Note 17 16:41:50.89 +36:28:54.2 R0 43.0 12.00 0.35 V SRb Os 18 16:41:24.06 +36:25:30.6 R0 41.25 12.32 0.10 V L Os;+long 19 16:41:31.98 +36:28:29.8 R0 ---- 12.08 0.17 V SR Os;P~30+long 20 16:41:23.55 +36:30:17.3 R0 ---- 12.08 0.16 V SR: Note;P=40: 21 16:41:33.43 +36:27:10.7 R0 ---- -- -- CST 22 16:41:41.27 +36:28:13.0 R0 ---- -- -- CST 23 16:41:41.60 +36:27:38.4 R0 ---- -- -- CST 24 16:41:41.91 +36:26:51.5 R0 45.0 11.97 0.22 V SRb Os 25 16:41:42.68 +36:27:31.0 R0 0.4296 -- 0.44 V RR1 26 16:41:45.23 +36:27:45.1 R0 ---- -- -- CST? Note 27 16:41:34.50 +36:27:52.3 R0 ---- -- -- CST 28 16:41:40.44 +36:27:29.9 R0 ---- -- -- CST 29 16:41:44.27 +36:28:31.7 R0 ---- -- -- CST 30 16:41:44.97 +36:27:04.0 R0 ---- -- -- CST 31 16:41:46.25 +36:28:55.2 R0 0.3193 14.432 0.113 V RR1 Note 32 16:41:23.04 +36:28:05.3 R0 ---- 14.12 0.08 V SR Note;P=33: 33 16:41:50.32 +36:24:15.6 R0 33.0 12.05 0.15 V SR Note 34 16:41:49.06 +36:27:07.7 R0 0.3893 14.828 0.320 V RR1 35 16:41:41.43 +36:27:47.1 R0 0.3200 -- 0.25 V RR1 36 16:41:43.45 +36:26:26.0 R0 0.3158 14.809 0.056 V RR1 multifreq 37 16:41:42.45 +36:28:21.8 R0 0.0494 17.18 0.65 V SXPHE Note 38 16:41:38.65 +36:25:37.7 R0 ---- 12.11 0.13 V SR Os;P=32: 39 16:41:42.51 +36:26:56.0 R0 56.0 11.96 0.25 V SR Os 40 16:41:49.66 +36:27:48.6 R0 33.0 12.07 0.14 V SR Os;+long 41 16:41:45.67 +36:27:57.4 R0 42.5 13.14 0.17 V Ell? Os;E? 42 16:41:35.49 +36:27:27.2 R0 40.0 11.94 0.17 V SR Os;+long 43 16:41:27.08 +36:28:00.2 R0 ---- 12.44 0.09 V L Os 44 16:41:39.15 +36:27:21.9 R0 ---- 12.11 0.12 V L Os 45 16:41:41.09 +36:27:22.7 R0 ---- 12.59 0.11 V L Os 46 16:41:41.35 +36:27:04.6 R0 0.0522 17.23 0.16 V SXPHE Note 47 16:41:38.77 +36:26:20.9 R0 0.0653 17.12 0.25 V SXPHE Note 48 16:41:42.89 +36:27:00.3 R0 0.223 19.96 0.44 V EC max;Note 49 16:41:42.96 +36:27:27.3 R0 ---- 19.15 0.19 V EA max;Note 50 16:41:32.43 +36:28:51.8 R0 0.0618 16.93 0.20 V SXPHE Note 51 16:41:51.99 +36:26:29.9 R0 ---- -- -- U ? Note 52 16:41:42.46 +36:28:08.1 R0 ---- 17.93 -- U CV? Note 53 16:41:44.57 +36:28:04.4 R0 ---- -- -- U ? Note 54 16:42:07.65 +36:29:36.5 R0 0.2954 14.90 0.16 V RR1 Note 55 16:41:48.47 +36:26:13.6 R0 0.0405 17.60 0.23 V SXP 56 16:41:45.63 +36:26:54.9 R0 0.0241 17.21 0.18 V SXP 57 16:41:21.37 +36:28:17.9 R0 0.2854 18.60 0.52 V EW 58 16:41:40.70 +36:27:16.2 R0 ---- 13.77 -- V L? Note 59 16:41:33.92 +36:30:05.5 R0 ---- 12.27 -- V SR? Note 60 16:41:44.53 +36:27:52.6 R0 ---- 14.47 -- V L? Note 61 16:41:41.89 +36:28:18.2 R0 11.42 13.13 -- V SR? Note 62 16:41:44.00 +36:22:33.9 R0 11.52 12.92 -- V SR? Note 63 16:41:32.53 +36:24:42.6 R0 27.1 12.175 0.08 V SR? Note 64 16:41:34.76 +36:27:59.5 R0 ---- 12.21 0.1 V L? Note 65 16:41:39.72 +36:26:37.6 R0 ---- 12.951 0.12 V L? Note PSR:A-F -- -- ---- -- -- PSR ====================================================================== Supplementary Notes A major paper on the variables in M13 was written by Kopacki et al. (2003). They investigated all of the variables numbered up to V45, with the exception of V14, 16, 20, 32 and 33 which were not in their field of view. These authors also published RA and dec (J2000) and an ID chart for the variable stars in their investigation. The positions, periods, magnitudes, amplitudes and classifications for V1-45 in the above table are from the Kopacki et al. (2003) paper unless indicated otherwise in the Notes. A designation "Os" in the Notes/Remarks column indicates that the periods, magnitudes, amplitudes and classifications are from a paper by Osborn et al. (2017). Their paper dealt with the long period variables in M13, i.e. the variables classified as type SR and L. The paper's Appendix contains supplementary material including details concerning each variable and unpublished observations. In a subsequent paper, Osborn et al. (2019) made a thorough investigation of the M13 Cepheid variables, based on more than a century of observations. The mean magnitudes, amplitudes and periods for these stars are from their investigation. These stars are designated "OsC" in the Notes/Remarks column. The data for the remaining variables are from the discovery papers unless indicated otherwise in the Notes. Deras et al. (2019) observed variables, V1-47, V50 and V54-62 and reported that all of the variables in their investigation were cluster members based on astrometric data from Gaia-DR2 (Gaia Collaboration 2018). They also listed the Gaia-DR2 sources for most of the variables in their investigation. In earlier studies, Cudworth & Monet (1979) and Cudworth (1979) derived membership probabilities for stars in M13. An important study of M13 was carried out by Ludendorff (1905). He listed 'delta RA' and 'delta Dec' for 1118 stars and his catalog numbers have been cited by many authors. Ludendorff's x,y positions have been converted to J2000 coordinates which are available through the Simbad database and from Vizier. ====================================================================== Notes on individual stars V10: Osborn (2019, private communication) pointed out that the suspected variable C6 (Deras et al. 2019) is very close to the star Sawyer (1940) identified as V10 Violat-Bordonau (2024) later showed that V10 (Ludendorff # 487) is constant and that C6 (Ludendorff #470) is variable. It is now listed as V65 (see below). Because of the proximity of these two stars, it is probable that their images were blended on some of the plates that Sawyer (1940) used for her study. As a result, the apparent variation of V10 was due to changes of seeing. The level of variation that Violat-Bordonau measured in V65 is well below the level that Sawyer could have detected on her photographs. V14: CST classification for V14 (Ludendorff #527) is from Sawyer (1955). The RA and dec are from Osborn (2000) V16: CST classification for V16 (Ludendorff #1079) is from Osborn & Ibanez (1973) and from Cudworth & Monet (1979). The RA and dec for V16 are from Osborn (2008, private communication) based on the 2MASS catalog. Samus et al. (2009) published RA, dec for V16, but their values pertain to a different star. V20: The RA and Dec are from Osborn (2000) and the remaining data are from Osborn et al. (2017). V26: Osborn (2019, private communication) commented that, based on the y coordinate of Kadla et al. (1980), V26 (X6) should be L753, instead of L748 as listed by Kopacki et al. (2003). The RA, dec listed above have been therefore revised to the values listed in the Vizier catalogue for L753. Since Kopacki's V26 was a different star, the "CST" classification is uncertain. V31: Deras et al. (2019) pointed out that V31 exhibited multifrequency oscillations V32: The RA and dec for V32 are from Osborn (2008, private communication) based on the 2MASS catalog and the remaining data are from Osborn et al. (2017). V33: The RA and Dec are from Osborn (2000) and the remaining data are from Osborn et al. (2017). V37: The data are from Kopacki (2005) V46, V47: The data are from Kopacki (2005) who showed that V46 is multiperiodic. V48, V49: The data are from the discovery paper by Pietrukowicz & Kaluzny (2004) who listed these stars as M13_03 and M13_04. V50: The data are from the discovery paper by Kopacki (2005). V51: This star was announced as star c, a suspected variable by Meinunger (1978). It was later observed by Kopacki et al. (2003) who did not detect any variability. They identified it as Ludendorff (1905) #993 and derived its RA and dec (J2000). They also pointed out that it had been identified as a UV-bright object by Zinn et al. (1972). Servillat et al. (2011) later detected U band variability in star c on timescales of a few days. The Kopacki observations were made in the V and I bands. The RA and dec listed above are from Servillat et al. (2011). The classification is uncertain. V52, V53: The data are from the discovery paper by Servillat et al. (2011). V54: The variability and RR1 classification for this star was confimed by Layden et al. (2020) as part of an ongoing study of the variables in M13. They pointed out that V54 is #1109 in the Ludendorff (1905) catalog. The period they derived, 0.295300 days, based on 14 datsets, was shorter than the Deras et al. value, which was 0.295374. Their V magnitude and amoplitude alsodiffered by a small amount. V58, V59, V60: The data are from the discovery paper by Deras et al. (2019) who published minimum V amplitudes of 0.07, 0.07 and 0.10 mag respectively. Their observations demonstrated that these stars are all located on the red giant branch of the CM diagram and exhibit long term variability, similar to the stars classified as L and SR by Osborn et al. (2017). Additional observations will be required before definitive classifications can be made. V61, V62: These stars, Ludendorff #592 and #687 (=IV-15) respectively, were listed as variables by McDonald et al. (2018) in a study of pulsation-triggered dust production by asymptotic giant branch stars. They published a period of 11 days for both stars. Neither had been confirmed as a variable in earlier studies of the long period variables by Osborn and his collaborators (e.g. Osborn et al. 2017). However, Deras et al. (2019) detected low level variations in both stars (Vamp > 0.02 and >0.03 respectively) and also derived periods of approximately 11 days. Therefore they are now tentatively classified as variables and the data in the above table are from Deras et al. McDonald et al. (2018) observed 4 other M13 stars which were previously known variables: Ludendorff (1905) #72 (=V18), #96 (=V43), #954 (=V33) and #973 (=V17). V63: Violat-Bordonau (2021) demonstrated the variability of V63 (=Ludendorff 199) by using it as a reference star for plotting light curves of three other stars L158, L77 and L353. All three stars appeared to have the same oscillations on the same dates, thus indicating that L199 was varying. The analysis was based on data obtained on 98 nights in 2019 and 134 in 2020, a span of 11 months. After consutation with Deras, it was established that the variability and period of L199 were confirmed in the data of Deras et al. (2019) as well. V64: This star (Ludendorff 261) was considered to be a candidate variable by Russeva & Russev (1980) but its variability was not confirmed by Osborn (2000) or by Kopacki et al. (2003). However, Deras et al. (2019) considered it to be a candidate variable, as well as a cluster member. They listed it as C3 in Table 3 of their paper. Its variability was subsequently confirmed by Violat-Bordonau (2022) based on their own observations, made in 2019, 2020 and 2021, along with ASAS-SN data obtained in the same time period. V64 is tentatively classified as irregular (L) because no single period fits all of the data. V65: This star (Ludendorff 470) was considered to be a candidate variable as well as a cluster member by Deras et al. (2019) who listed it as C6 in Table 3 of their paper. Its variability was subsequently confirmed by Violat-Bordonau (2024) based on their own observations, made in 2019, 2020 and 2021, along with ASAS-SN data obtained between January 2019 and November 2023. V65 is tentatively classified as irregular (L) because no single period fits all of the data. However, Violat-Bordonau (2024) noted that the star also exhibits short period oscillations that might be due to binary ellipsoidal variability. In fact, it was classified as an ellipsoidal by Green et al. (2023). ============================================================================= Discovery of the variable stars in M13 (NGC 6205): A good discussion of the history of the investigations of variable stars in M13 was given by Kopacki et al. (2003). V1-2 Bailey (1902) with ID chart (Plate X, p252.19) and x,y coordinates (p241) V3-6 = Ludendorff 135, 322, 806 (north component of a double) and 872 Shapley (1915a) who listed the Ludendorff (1905) catalogue numbers. The numbers V3 to V6 were assigned by Sawyer (1940) V7 = Ludendorff 344 Shapley (1915b) who identified it by its Ludendorff number Shapley also noted that Barnard (1914) had called attention to this variable and published its 1902 RA and dec. The number V7 was assigned by Sawyer (1940) V8-11 Sawyer (1940) who listed Ludendorff numbers, x,y positions and published an ID chart for V1-11 V1 = L816, V2 = L306, V3 = L135, V4 = L322, V5 = L806_beta, V6 = L872, V7 = L344, V8 = L206, V9 = L806_alpha, V10 = L487, V11 = L324 V12-14 = Ludendorff #187, 327, 527 Kollnig-Schattschneider (1942). The numbers V12-14 were assigned by Sawyer (1955) in her 2nd catalogue. Sawyer (1955) also pointed out that the variable identified as L200 by Kollnig-Schattschneider should have been L206 (now known as V8) The RA and dec we list for V14 are from Osborn (2000) - Table 5. V15 = Ludendorff #835 Arp (1955a,b): V15 was labelled in Fig. 3 by Arp (1955a). In Arp (1955b), V15 is labelled as star IV-48 in Fig 2 and Table 1 where it is described as an irregular variable. Sawyer (1955) listed V15 and its Ludendorff number (835) in her 2nd catalogue based on correspondence with Arp. V16 = #A18 of Savedoff (1956) = Ludendorff #1079 This variable was announced by Sawyer Hogg (1973) who noted that it was discovered by Tsoo Yu-hua who had sent her a finding chart. Sawyer Hogg identified V16 as Savedoff A18 which was probably Ludendorff #1113, but Cudworth & Monet (1979) found that Savedoff A18=Ludendorff #1079. Osborn (2008, private communication to C Clement) examined a photocopy of Tsoo's finding chart provided by Sawyer Hogg and confirmed that V16 = A18 = L1079. He also provided the RA and dec which are listed above, based on the 2MASS catalog. In addition, Sawyer Hogg (1973) noted that Tsoo discovered a variable in the surrounding field. These 2 suspected variables were also mentioned in Sawyer Hogg's (1967) IAU report. V17 = Ludendorff #973 = Arp (1955b) I-48 Russev (1974) indicated that L973 might be variable and this was confirmed by Fuenmayor & Osborn (1974). The number V17 was assigned by Clement (1997) in the first electronic update of the Sawyer Hogg (1973) catalogue. V18-20 = Ludendorff #72, 194, 70 These variables were announced by Russeva & Russev (1980) who listed their Ludendorff (1905) numbers. The numbers V18, V19, V20, were assigned by Clement (1997) in the first electronic update of the Sawyer Hogg (1973) catalogue. V19 (L194) had been previously announced as a supected variable by Kadla et al. (1976). V20 (L70) was previously suspected to be variable by Pike & Meston (1977) who identified it as Arp (1955b) II-67. The RA and dec listed for V20 are from Osborn (2000). Russeva & Russev also indicated that L240 and L261 met their suspected variability criterion, but gave no further discussion of these two stars. L240 and L261 were not listed as variables in previous versions of this file, above table because Osborn (2000) observed them both and did not detect any variabiity. L261 was also observed by Kopacki et al. (2003) who did not detect any variability. However, based on more extensve data, Violat-Bordonau (2022) concluded that L261 is variable. Therefore it is now listed as V64. V21-31 = Stars X1-11 listed with x,y positions by Kadla et al. (1980) who also included Ludendorff numbers for some of the variables: X1=L216, X4=L598, X7=L254, X8=L569, X9=L717, X10=L743, X11=L807 Kopacki et al. (2003) later listed Ludendorff numbers for the remaining variables: X2=V22=L568, X3=V23=L575, X5=V25=L630, X6=V26=L748. They also listed V28 as L519 instead of L569 which had been the designation published by Kadla et al. In an earlier paper, Kadla et al. (1976) announced that X4 (=L598=B140) was probably variable. The numbers V21-31 were assigned by Clement (1997) in the first electronic update of the Sawyer Hogg (1973) catalogue and the RA and dec (2000) listed in the above table are from Kopacki et al. (2003). V32 = Ludendorff #66 Russeva et al (1982) who listed the Ludendorff number. The RA and dec have been provided by Osborn (2008, private communication) based on the 2MASS catalog. The number V32 was assigned by Clement (1997) in the first electronic update of the Sawyer Hogg (1973) catalogue. Russeva et al (1982) also confirmed the variability of V24 (=X4=L598) previously announced by Kadla et al. (1980) V33 = Ludendorff #954 announced by Welty (1985) with Ludendorff number The RA and dec listed above are from Osborn (2000) The number V33 was assigned by Clement (1997) in the first electronic update of the Sawyer Hogg (1973) catalogue. V34-37 Kopacki et al (2003) with ID chart, RA and dec V38 = Ludendorff #414 Russev (1973) and Russev (1974) indicated that L414, might be variable but Fuenmayor & Osborn (1974) could not confirm this in their observations. However, Kopacki et al. (2003) detected variability and assigned the number V38. V39-40 = Ludendorff #629, 940 Osborn (2000) with RA, dec (J2000) and Ludendorff numbers Osborn concluded that the variablility was certain for L629 and possible for L940. Kopacki et al. (2003) found both stars to be variable and assigned the numbers V39 and V40. V41-45 Kopacki et al. (2003) with ID chart, RA and dec (J2000) V46-49 = M13_01 to M13_04 announced by Pietrukowicz & Kaluzny (2004) with RA and dec (epoch 2000). The numbers V46-49 were assigned by Kopacki (2005) V50 Kopacki (2005) with ID chart, RA and dec (J2000) The positions of V37, V46, and V47 were also labelled on the ID chart V51 = suspected variable star c of Meinunger (1978) who published an ID chart. Servillat et al. (2011) confirmed variability from U data and derived its RA and dec and published an ID chart. It was variable #7 in their study. The number V51 has been assigned in this catalogue. V51 is also L993 (Lundendorff 1905), IV-52 (Arp 1955b) and star #3 on the list of UV bright stars in M13 (Zinn et al. 1972). V52 = variable #4 of Servillat et al. (2011) who derived RA and dec (J2000) and published an ID chart. They concluded that this star is the optical counterpart of Chandra source X6. The number V52 has been assigned in this catalogue. V53 = variable #2 of Servillat et al. (2011) who derived RA and dec (J2000) and published an ID chart. The number V53 has been assigned in this catalogue. V54-60: Deras et al. (2019) with ID chart and RA and dec (epoch 2000) These authors announced an additional 6 variable star (SR type) candidates (C1-C6) that are cluster members, 5 candidate variables (C7-C11) with uncertain membership status, and 4 others (C12-C15) that are definitely not cluster members. Deras et al. also investigated and made comments on the RR Lyrae variables detected in the field of M13 by Clementini et al. (2018) in the Gaia-DR2 study. (See Table 4 of the Deras et al. paper.) V61-62 = Ludendorff #592 and IV-15 (=L687) McDonald et al. (2018) listed L592 and IV-15 as AGB variables in their study of pulsation-triggered dust production by asymptotic giant branch stars. For the above table, the RA and dec (epoch 2000) for these stars have been obtained from the Vizier website where Ludendorff's (1905) original table has been posted. Cudworth & Monet (1979) noted that IV-15 = Ludendorff #687. The numbers V61 and V62 were assigned by Deras et al. (2019) in a "Note added in proof" to their paper. In an earlier paper, White (1981) noted that L687 (now V62) might be variable. However, Welty (1985) did not see strong evidence for its variability and his conclusion was supported by Osborn (2000) so L687 was not previously listed in this catalogue. White (1981) also pointed out that Ludendorff #773 and #961 were suspected variables, but their variability was not confirmed by Welty (1985) so these stars have not been listed. V63 = Ludendorff #199 Violat-Bordonau (2021) with RA, dec and an ID chart with Ludendorff #199 labelled V64 = Ludendorff #261 Violat-Bordonau (2022) with RA, dec and an ID chart with Ludendorff #261 labelled V65 = Ludendorff #470 Violat-Bordonau (2024) with RA, dec and an ID chart with Ludendorff #470 and a few other nearby variables labelled PSR: According to Paulo Freire's website, there are 6 millisecond pulsars in M13. (www.naic.edu/~pfreire/GCpsr.html) The 6 MSPs in M13 have been discussed by Zhao et al. (2021). ----------------------------------------------------------------- Kadla et al. (1976) indicated that L222 (=Barnard 29), a known binary star, might be variable, but did not mention it in their 1980 paper. Kopacki et al (2003) observed L222 and did not detect any variability. Barnard 29 is a UV-bright star whose evolutionary status has been discussed by Dixon et al. (2019) ------------------------------------------------------------------ Meinunger (1978) announced 3 suspected variables, which she labelled as a,b,c on ID charts that also included V6 and V15. Kopacki et al. (2003) discussed these three stars. Star a (Ludendorff #765) was outside their field of view. Variability of star a has not been detected in any subsequent studies. Star b was a blend of two stars on their CCD frames and therefore unlikely to be variable. Star c is now known as V51. (see above) ================================================================== References Arp, H. 1955a, AJ, 60, 1 Arp, H. 1955b, AJ, 60, 317 Bailey, S. I. 1902, Harvard Annals, 38 Barnard, E. E. 1914, ApJ, 40, 179 Clement, C. M. 1997, AAS Newsletter, 84, 15 Clementini, G. et al. 2018, arXiv:1805.02079 Cudworth, K. 1979, AJ, 84, 1005 Cudworth, K. & Monet, D. G. 1979, AJ, 84, 774 Deras, D., Arellano Ferro, A., Lazaro, C., Bustos Fierro, I. H., Calderon, J. H., Muneer, S., Giridhar, S. 2019, MNRAS, 486, 2791 Dixon, W. V., Chayer, P., Reid, I. N., Bertolami, M., Miguel, M. 2019, arXiv:1903.00350 Fuenmayor, F. & Osborn, W. 1974, IBVS, 952 Gaia Collaboration; Brown, A. G. A. and 452 co-authors, 2018, A&A, 616A, 1G Green, J., Maoz, DF., Mazeh, T., Faigler, S., Shahaf, S., Gomel, R., El-Badry, K., Rix, H.-W. 2023, MNRAS, 522, 29 Kadla, Z. I., Antal, M., Zdarsky, F., Spasova, N. 1976, Sov. Ast., 20, 403 = English translation of Kadla et al. 1976, Astron. Zhurnal, 53, 713 Kadla, Z. I., Gerashchenko, A. N., Yablokova, N. V. 1980, Ast. Tsirk., 1136, 5 Kollnig-Schattschneider, E. 1942, A. N., 273, 145 Kopacki, G. 2005, Acta Ast., 55, 85 Kopacki, G., Kolaczkowski, Z., Pigulski, A. 2003, A&A, 398, 541 Layden, A., Osborn, W., Pritzl, B. L., Smith, H. A. 2020, Research Notes of the AAS, 4, 17. Ludendorff, H. 1905, Potsdam Publ 15, Nr. 50 McDonald, I., De Beck, E., Zijlstra, A. A., Lagadec, E. 2018, MNRAS, 481, 4984 Meinunger, I. 1978, Mitt. Verlander. Sterne Sonneberg, 8, 69 Osborn, W. 2000, AJ, 119, 2902 and erratum (2000, AJ 120, 2730) Osborn, W. 2002, AJ, 124, 3492 Osborn, W. & Fuenmayor, F. 1977, AJ, 82, 395 Osborn, W. & Ibanez 1973, IBVS, 798 Osborn, W., Layden, A., Kopacki, G., Smith, H., Anderson, M., Kelly, A., McBride, K., Pritzl, B. 2017, Acta Ast., 67, 131 plus Appendix materials at ftp://ftp.astrouw.edu.pl/acta/2017/osb_131/ (Os) Osborn, W., Kopacki, G., Smith, H. A., Layden, A., Pritzl, B., Kuehn, C., Anderson, M., 2019, Acta Ast., 69, 101 (OsC) Pietrukowicz & Kaluzny 2004, Acta Ast., 54, 19 Pike, C. D. & Meston, VC. J. 1977, MNRAS, 180, 613 Russev, R. M. 1973, Per. Zvez., 19, 181 Russev, R. M. 1974, Astron. Zhurnal, 51, 122 [English translation: Rusev, R. M. 1974, Sov. Ast., 18, 71] Russev, R. M. & Russeva, T. 1979a, IBVS, 1534 Russev, R. M. & Russeva, T. 1979b, IBVS, 1624 Russeva, T. S., Illiev, L., Russev, R. 1982, IBVS 2223 Russeva, T. S. & Russev, R. 1980, IBVS, 1769 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Savedoff, M. P. 1956, AJ, 61, 254 Sawyer, H. B. 1940, DDO Pub., 1, No. 5, p179 Sawyer, H. B. 1955, DDO Pub., 2, No. 2, p33 (2nd catalogue) Sawyer Hogg, H. 1967, IAU Transactions XIIIA, page 556. Sawyer Hogg, H. 1973, Publ. DDO, 3, No. 6 (3rd catalogue) Servillat, M., Webb, N. A., Lewis, F., Knigge, C., van den Berg, M., Dieball, A., Grindlay, J. 2011, ApJ, 733, 106 Shapley, H. 1915a, PASP, 27, 134 Shapley, H. 1915b, PASP, 27, 238 Violat-Bordonau, F. 2021, Open European Journal on Variable Stars (OEJV), Vol. 213, p1-10 Violat-Bordonau, F. 2022, Open European Journal on Variable Stars (OEJV), Vol. 222, p1 Violat-Bordonau, F. 2024, Open European Journal on Variable Stars (OEJV), January Welty, D. E. 1985, AJ, 90, 2555 White, R. E. 1981, in Astrophysical Parameters for Globular Clueters, IAU Colloq. 68, ed. A. G. D. Philip and D. S. Hayes, p 161 Zhao, J., Zhao, Y., Heinke, C.O. 2021, MNRAS, 502, 1596 Zinn, R. J., Newell, E. B., Gibson, J. B. 1972, A&A, 18, 390 ===================================================================