NGC 6341 / C1715+432 / Messier 92 (Updated September 2021) RA: 17:17:07.39 DEC: +43:08:09.4 (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 17:17:18.99 +43:08:54.9 R0 0.7028 15.02 0.86 V RR0 2 17:17:15.64 +43:09:22.4 R0 0.6439 15.08 0.85 V RR0 3 17:17:12.00 +43:12:25.3 R0 0.6377 15.09 1.17 V RR0 4 17:17:00.35 +43:09:09.1 R0 0.6289 15.12 0.84 V RR0 5 17:17:14.93 +43:07:19.2 R0 0.6197 15.12 0.98 V RR0 6 17:17:10.87 +43:08:56.0 R0 0.6000 14.96 1.09 V RR0 7 17:17:07.61 +43:07:21.6 R0 1.0614 14.149 0.67 V AC Note 8 17:17:26.24 +43:11:42.5 R0 0.6728 15.05 0.67 V RR0 9 17:17:09.09 +43:07:24.2 R0 0.6085 15.13 1.19 V RR0 10 17:17:14.93 +43:08:49.3 R0 0.3773 15.11 0.48 V RR1 11 17:17:13.98 +43:07:05.8 R0 0.3084 15.10 0.62 V RR1 12 17:17:10.25 +43:06:34.8 R0 0.4100 15.06 0.41 V RR1 Note 13 17:17:21.48 +43:07:13.9 R0 0.3015 15.176 0.049 V RR1 Note 14 17:16:38.24 +43:12:14.5 R0 0.2951 14.31 0.40 V EW f;Note 15 17:17:07.32 +43:09:30.9 R0 ---- -- -- CST 16 17:16:47.91 +43:06:16.0 R0 ---- -- -- CST Note 17 17:16:59.12 +43:08:23.9 R0 ---- -- -- CST 18 17:16:57.22 +43:07:11.5 R0 ---- -- -- CST 19 17:16:58.51 +43:07:44.3 R0 ---- -- -- CST 20 17:17:04.4 +43:07:45 R0 ---- -- -- CST 21 17:17:07.2 +43:08:53 R0 ---- -- -- CST 22 17:17:07.4 +43:07:50 R0 ---- -- -- CST 23 17:17:07.4 +43:08:33 R0 ---- -- -- CST 24 17:17:07.5 +43:08:41 R0 ---- -- -- CST 25 17:17:09.73 +43:08:03.5 R0 0.7004 -- 0.75 V RR0 26 17:17:10.73 +43:09:58.8 R0 ---- -- -- CST 27 17:17:11.1 +43:08:08.1 R0 ---- -- -- CST 28 17:17:12.2 +43:08:27 R0 ---- -- -- CST 29 17:17:07.94 +43:08:02.8 R0 0.5959 -- 0.95 V RR0 f;Note 30 17:17:07.53 +43:08:06.0 R0 0.5283 -- 1.59 V RR0? f;Note 31 17:17:06.77 +43:08:27.3 R0 0.3982 -- 0.52 V RR1 f;Note 32 17:17:04.60 +43:08:42.2 R0 0.3246 -- 0.21 V RR1 33 17:17:03.85 +43:08:13.7 R0 0.0751 17.29 0.68 V SXP 34 17:17:09.95 +43:07:42.7 R0 0.0830 17.13 0.34 V SXP f;Note 35 17:17:09.49 +43:08:38.0 R0 0.0549 -- -- SXP 36 17:17:06.52 +43:07:57.4 R0 0.0475 17.88 0.04 V SXP f;Note 37 17:17:06.33 +43:09:48.3 R0 0.0402 -- -- SXP 38 17:17:04.59 +43:08:45.2 R0 0.0729 -- -- SXP 39 17:17:04.24 +43:08:50.4 R0 0.0359 -- -- SXP 40 17:17:02.44 +43:08:48.0 R0 0.2766 15.191 0.174 V RR Note 41 17:17:17.80 +43:05:33.7 R0 0.0559 17.207 0.650 V SXP 42 17:17:08.00 +43:07:42.1 R0 ---- 12.052 0.180 V SR? PSR msP ====================================================================== Supplementary Notes A good summary of the twentieth century investigations of variables in M92 was given by Kopacki (2001). V1-32 The RA and dec are from Samus et al. (2009). The periods, magnitudes, amplitudes and classifications are from Kopacki (2001) unless indicated otherwise in the notes on individual stars. V14 and V16 were outside Kopacki's (2001) field of view. The CST classification for V15, V17, V18, V19, V20, V21, V22, V23, V24, V26, V27, and V28 are all from Kopacki's (2001) paper. V33-39 These are SX Phe variables and all of their data are from Kopacki (2007). They were also observed by Yepez et al. (2020) who confirmed Kopacki's periods. Yepez et al. also derived mean magnitudes for all of them, but noted that their photometry was contaminated by neighbouring stars. Therefore their magnitudes have not been included in the above table. V40-42 All the data are from the discovery paper by Yepez et al. (2020) ======================================================================= Notes on individual stars V7: The period, magnitude, amplitude and classification are from Osborn et al. (2012). They noted that both Matsunaga et al. (2006) and Di Criscienzo et al. (2007) had pointed out that V7 must be an anomalous Cepheid (AC) because it is too bright to be a BL Her star. The AC classification was confirmed by Yepez et al. (2020). V12: Some confusion about the identity of this star arose because there was an error in the sign of the x coordinate published by Hachenberg (1939). It should have been +29.9" instead of -29.9". The incorrect value was published by Sawyer in her three catalogues (Sawyer 1939, 1955; Sawyer Hogg 1973). Bartolini et al. (1968) discovered the error and recognized that V12 was the same star as Nassau's V10 which had been designated as V15 by Sawyer (1939, 1955) in her first two catalogues. V13: The period, magnitude and amplitude are from Yepez et al. (2020) who detected two modes of pulsation, with periods of 0.301536 and 0.337182 days. They concluded one of the modes must be non-radial. V14: This star was classified as W Ursae Majoris by Hachenberg (1939) who derived a period of 0.346178 days and noted that it did not belong to the cluster. The non-member status was later confirmed in proper motion studies by Rees (1992) and by Tucholke et al. (1996). It is listed as V798 Her in the Moscow GCVS. The period, magnitude, amplitude and classification listed above are from the Catalina survey (Drake et al. 2014) where it was listed as CSS_J171638.42+431214. According to the Vizier website, this period and classification have been confirmed by other surveys, such as ASAS-SN, ATLAS, LINEAR and WISE. It appears that the period derived by Hachenberg (1939) was an alias. V16: This was Nassau's suspected variable V15. It was subsequently established by Arp et al. (1953) that it was not variable and this result was confirmed by Walker (1955). V29, V30, V31, V34, V36: The field status for these variables was reported by Yepez et al. (2020) based on proper motion data taken from Gaia-DR2. V30: Yepez et al. (2020) concluded that V30 might be a BL Her, and not an RR Lyrae variable, based on its anomalous location on the period-amplitude relation and the shape of its light curve. In any case, they did not consider it to be a cluster member. V40: Yepez et al. (2020) concluded that V40 must be a double-mode pulsator. The maximum and minimum magnitudes varied from cycle to cycle and they derived two periods, 0.276639 and 0.201314 days, respectively. Their 0.27 day period is listed in thr above table. V41: Yepez et al. (2020) identified three active freqencies for V41, corresponding to periods of 0.055947, 0.054350 and 0.057632 days, respectively. ==================================================================== Discovery of the variable stars in M92: V1-14 Hachenberg (1939) with x,y positions and numbers from the Hopman (1930) catalogue. Hachenberg noted that these variables had been previously discovered by Woods (1922) and Guthnick & Prager (1925). Woods announced the discovery and published x,y coordinates for the variable now known as V11. Guthnick & Prager (1925) announced that they had discovered 13 variables in M92, but did not publish any positions. The numbers V1-14 were assigned by Hachenberg. Most of these variables were independently discovered by Nassau (1938) who published an ID chart. However, the Nassau and Hachenberg numbering systems were different. Sawyer (1939, 1955) adopted Hachenberg's (1939) system in her catalogues. A table with cross correlations between the different numbering systems was published by Kadla et al. (1983). V15 = V12 of Nassau (1938) who labelled it on a chart The number V15 was assigned by Sawyer Hogg (1973) in her 3rd catalogue. In her first two catalogues (Sawyer 1939, 1955), she designated this star as V16 and Nassau's V10 was designated as V15. Bartolini et al. (1968) later discovered that Nassau's V10 was the same star as Hachenberg's V12. Sawyer (1939, 1955) had not realized this because the x coordinate Hachenberg (1939) published for his V12 was incorrect. V16-17 = Nassau's (1938) suspected variables V15-16 which he labelled on an ID chart. Their x,y coordinates were derived by Kadla et al. (1983) and the numbers V16-17 were later assigned by Clement et al. (2001) in accordance with the system established by Kadla et al. (1983). V18-28 Kadla et al. (1983) with x,y coordinates and an ID chart They also published a table with cross correlations between the numbering systems of Sawyer (1939,1955), Sawyer Hogg (1973) and Nassau (1938) for V1-17. Kopacki (2001) observed all of these starss and concluded that only one of them (V25) is variable. Thus the CST classification for all of the others in the above table is based on Kopacki's (2001) investigation. V29-34 Kopacki (2001) with x,y coordinates and an ID chart V35-39 Kopacki (2007) with RA, dec and ID chart Kopacki also provided ID for 3 blue stragglers suspected of variability. V40-42 Yepez et al. (2020) with RA, dec and ID chart. They also discovered an RR1 variable which they numbered F1 because it is probably not a cluster member and a probable variable which they labelled as C1. PSR Pan et al. (2020) reported the discovery of an eclipsing binary millisecond pulsar: PSR J1717+4308A (M92A) with FAST (the Five-hundred-meter Aperture Spherical Radio telescope). Its pulse frequency was 316.5 Hz (3.15 ms) and it is a member of a binary system with an orbital period of 0.2 days. ---------------------------------------------------------------- Walker (1955) suspected that three stars near the RG tip might be variable, but Welty (1985) did not detect any variablility with B amplitude greater than 0.2 mag for any of them. ---------------------------------------------------------------------- Shara et al. (1994) surveyed the cluster for erupting dwarf novae but did not detect any; they established an upper limit based on their results. Tuairisg et al. (2003) later announced a possible dwarf nova candidate. ----------------------------------------------------------------------- Lynch & Ransom (2011) conducted a search for pulsars, but did not find any in M92. -------------------------------------------------------------- In a search for RR Lyrae in stellar streams that might have escaped from globular clusters, Abbas et al. (2021) found one candidate RR Lyrae variable that might be associated with M92: (CSS_J171728.4+424514 in the Catalina survey). ============================================================ References Abbas, M., Grebel, E. K., Simunovic, M. 2021, ApJ, 915, 49 Bartolini, C., Battistini, P., Nasi, E. 1968, Bologna Publ., 9, No. 15 Clement, C. M., Muzzin, A., Dufton, Q., Ponnampalam, T., Wang, J., Burford, J., Richardson, A., Rosebery, T. 2001, AJ, 122, 2587 Di Criscienzo, M., Caputo, F., Marconi, M., Cassisi, S. 2007, A&A, 471, 839 Drake, A.J., Graham, M. J., Djorgovski, S. G., Catelan, M., Mahabal, A. A., Torrealba, G., Garcia-Alvarez, D. and 14 coauthors, 2014, ApJS, 213, 9 Guthnick, P. & Prager, R. 1925, Sitz. d. Preuss., Akad. Wiss., 28, 508 Hachenberg, O. 1939, Z. Astrophys. 18, 49 Hopmann, J. 1930, Mem. Pont. Acc., 14 Kadla, Z. I., Yablokova, N. V., Gerashchenko, A. N., Spasova, N. 1983, Per. Zvez., 21, 827 Kopacki, G. 2001, A&A, 369, 862 Kopacki, G. 2007, Acta A, 57, 49 Lynch, R. 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