NGC 6522 / C1800-300 RA: 18:03:34.08 DEC: -30:02:02.3 (J2000) (Most recent updates: Membership probability flag - 2024; Remaining data - November 2024) ============================================================ Bytes Format Explanation 1-8 A8 Star ID 10-32 A11,1x,A11 Position 34-35 A2 Membership probability flag based on data published by Prudil & Arellano Ferro (2024) m1: prob >=0.85; m2: prob >=0.7 and <0.85; m3: prob >= 0.5 and <0.7; f: prob <0.5 u: no data available 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 Mem Period ampl C Type Notes/ RA Dec Flag Remarks ========================================================================= 1 18:03:29.98 -30:01:30.3 m1 0.2700 16.799 0.523 V RR1 2 18:03:35.23 -30:01:25.0 f 0.4741 16.686 1.062 V RR0 3 18:03:36.32 -30:01:27.6 m1 0.2887 16.853 0.479 V RR1 4 18:03:37.15 -30:01:56.7 m2 0.5638 16.721 0.969 V RR0 Note 5 18:03:40.25 -30:02:47.7 m1 0.2868 16.867 0.487 V RR1 6 18:03:42.58 -30:01:34.7 f 0.1613 17.210 -- V DSCT f;Note 7 18:03:31.21 -30:01:01.9 f 700.0 15.7 0.69 V L? f;Note 8 18:03:33.63 -30:01:15.1 m1 1.7480 15.591 1.243 V CW Note 9 18:03:33.63 -30:03:09.3 f 0.2987 16.262 0.446 V RR1 f 10 18:03:35.15 -30:02:00.4 m1 0.5574 16.361 0.667 V RR0 f? 11 18:03:35.19 -30:02:02.5 m1 0.6158 16.498 -- V RR0 f? 12 18:03:29.88 -30:01:56.7 f 0.2569 16.641 0.248 V RR1 f 13 18:03:34.28 -30:01:45.0 m1 0.6360 16.660 0.929 V RR0 14 18:03:35.40 -30:01:55.3 f 0.3281 16.519 0.278 V RR1 f 15 18:03:36.10 -30:01:52.1 m1 1.7972 15.611 0.988 V CW Note 16 18:03:29.18 -30:02:49.4 m1 55.87 14.040 0.66 V SR 17 18:03:34.59 -30:02:00.3 m1 11.9158 14.014 0.13 V OSARG 18 18:03:34.85 -30:02:11.5 m1 23.597 14.272 0.08 V OSARG 19 18:03:34.99 -30:01:56.3 m1 14.922 14.467 0.06 V OSARG 20 18:03:35.20 -30:02:10.7 m1 51.18 14.118 0.12 V OSARG 21 18:03:35.27 -30:03:02.6 m1 16.948 13.758 0.12 V OSARG 22 18:03:37.92 -30:02:07.4 m1 17.827 14.200 0.11 V OSARG 23 18:03:38.19 -30:00:51.7 m1 12.131 14.297 0.05 V OSARG 24 18:03:36.13 -30:01:48.7 f 0.4644 16.476 0.42 V RR1 Note 25 18:03:34.55 -30:01:38.0 f 1.4624 13.85 0.272 G CW? 26 18:03:32.57 -30:01:57.6 f ---- 13.45 0.112 G SR   PSR 6 msPs ================================================================== Supplementary Notes NGC 6522 is a core collapsed globular cluster in the Galactic bulge. It has a core radius of 0.05 arcminutes, a 1.0 arcminute half-light radius and [Fe/H] = -1.34 according to the 2010 update to the Harris (1996) catalogue. The data in the above table are from a paper from Arellano Ferro et al. (2023, hereafter AF23). Their investigation was based on an analysis of OGLE and Gaia observations (Soszynski et al. 2013, 2014; Gaia Collaboration 2023). For each variable, they listed the OGLE and/or Gaia identification number and they published an identification chart for the variables using an OGLE I-band image. They did not publish the mean magnitudes and amplitudes in their paper; these have been obtained from Arellano Ferro (2024, private communication). They also carried out an analysis of membership status using data from the Gaia-DR3 (2023) catalogue. The stars they found to be field stars are designated "f" in the Notes column in the above table. The field around NGC 6522 was observed by Baade (1946, 1951) in his investigations to characterize the nature of the nucleus of the Milky Way galaxy and to determine its distance from the Sun. He used the Mount Wilson 100-inch telescope to study the field within 16 arcminutes of the cluster and discovered 285 variable stars. Their elements were later published by Gaposchkin (1955). This field is now known as "Baade's window" because it is an area with relatively low absorption near the Galactic centre and has been the subject of many studies. ================================================================= Notes on individual stars V4: There has been confusion about the variability status of V4 because of an identification error. It was one of the variables discovered by Baade (1946, 1951) and its elements were later published by Gaposchkin (1955) who listed the star as #170. Unfortunately, the star was incorrectly labelled on his 1955 plate. V4 is located about 20 arcsecs southwest of the star he labelled as G#170. As a result, subsequent investigators (Clube 1965, Blanco 1984, Walker & Mack 1986) did not detect the variability of "V4" because it was in a crowded field and they were looking at the wrong star. In a later paper, Gaposchkin (1956) published a hand-drawn finder chart that showed the correct position for G#170 relative to nearby stars within approximately 15 arcseconds. Unfortunately, the star he identified as #170 in the earlier paper did not appear on the chart and this made his chart hard to decipher. In the meantime, Clube (1965) announced a new RR Lyrae variable which he numbered V7 and identified on a plate obtained with the Radcliffe 74-inch reflector. Sawyer Hogg (1973) designated this "new" variable as V10 in her 3rd catalogue. However, it turns out that Clube's new variable was Baade's original V4. Its location matches the position published on Gaposchkin's (1956) finder chart and the (Baade) x,y coordinates that Sawyer (1955) listed for V4. Furthermore, the period Clube derived for his new variable, 0.564 days, agrees with 0.56383 days, the period that Gaposchkin (1955) published for his star #170. It was therefore listed as V4 in an earlier version of this catalogue. Subsequently, an RR Lyrae variable with the same period, 0.56383333 days was observed in the Ogle IV survey (Soszynski et al. 2014) in a location close to the position of V4. They listed it as OGLE-BLG-RRLYR-12132 and their data were listed for V4 in an earlier version of this catalogue. However, it was about 2 mags fainter than the other RR Lyrae variables which was problematic. The saga continues. In their investigation, AF23 noted the Ogle IV magnitudes for this star were also significantly fainter than their Ogle III magnitudes. Furthermore, no variable was recovered at this position in the Gaia data. On the other hand, both the Ogle and Gaia databases included a variable star, with the same period, located about 2 arcseconds southwest of the published position for OGLE-BLG-RRLYR-12132. AF23 concluded that the light from the two sources was mutually contaminated and that the real V4 was the variable that was detected in the Gaia data. In their diagrams, they labelled the fainter source as COG. V6: This star is Gaposchkin (1955) #247, Blanco (1984) #64 and BWC V82 of Udalski et al. (1994). According to McNamara et al. (2000), BWC V82 is a high amplitude Delta Scuti variable (HADS) in the Galactic bulge. Its period is too long for an SX Phe variable and thus it is not a cluster member, a conclusion confirmed by A23. V24: AF23 found that this star exhibited strong period modulations. ============================================================ Discovery of the variable stars in NGC 6522: V1-9 = Gaposchkin # 222, 133, 44, [170?*], 37, 247, 172, 27, 232 labelled on a photograph published by Gaposhkin (1955) who also listed their 1900 RA and dec. Sawyer (1955) assigned the numbers V1-9 and published x,y coordinates in consultation with Baade (private correspondence). In his correspondence with Sawyer (1955), Baade also indicated that V7, V8 and V9 were field stars. Therefore they are listed in the GCVS as V3900, V1437, V1438 Sgr respectively. *Gaposchkin #170 (V4): Sawyer (1955, 1973) published the correct x,y coordinates for this star. However, it was incorrectly labelled on Gaposchkin's (1955) plate. See the note above, for V4. V10-11 = OGLE-BLG-RRLYR-12115, OGLE-BLG-RRLYR-12114 identified by RA and dec in the Ogle III survey (Soszynski et al. 2011a) who assigned the numbers V10-11. V12 = Blanco (1984) #54 = V4113 Sgr = OGLE-BLG-RRLYR-12072 Blanco published RA and dec (Epoch 1950) and an ID plate. The number V12 was assigned in an earlier version of this catalogue. V13 = OGLE-BLG-RRLYR-12108 identified by RA and dec in the Ogle III survey (Soszynski et al. 2011a). The number V13 was assigned in an earlier version of this catalogue. V14 = OGLE-BLG-RRLYR-33606 identified by RA and dec in the Ogle IV survey (Soszynski et al. 2014). The number V14 was assigned in an earlier version of this catalogue. V15 = OGLE-BLG-T2CEP-284 identified by RA and dec in the OGLE III Catalogue of Type II Cepheids in the Galactic Bulge (Soszynski et al. 2011b) The number V15 was assigned in an earlier version of this catalogue. V16-23 In the OGLE III survey of Long period Variables in the Galactic Bulge, Soszynski et al. (2013) identified eight long period variables within 2 arcminutes of the cluster centre and with less than 14.5 mag. Arellano Ferro et al. (2023) determined that they are all members and assigned the numbers: V16 = OGLE-BLG-LPV-193749 (r=1.31') SRV = V5466 Sgr V17 = OGLE-BLG-LPV-194243 (r=0.13') OSARG V18 = OGLE-BLG-LPV-194274 (r=0.23') OSARG V19 = OGLE-BLG-LPV-194290 (r=0.23') OSARG V20 = OGLE-BLG-LPV-194311 (r=0.29') OSARG V21 = OGLE-BLG-LPV-194316 (r=1.02') OSARG V22 = OGLE-BLG-LPV-194544 (r=0.84') OSARG V23 = OGLE-BLG-LPV-194566 (r=1.49') OSARG The classification OSARG means OGLE small amplitude red variable. V24 This variable was listed in both the Ogle and Gaia surveys. AF23 assigned thee number V24. V25-26 These are variables that were reported in Gaia-D3, but not announced in the other studies. AF23 confirmed their variablility and assigned the numbers V25-V26. -------------------------------------------------------------------- In the OGLE IV galactic bulge survey, (Soszynski et al. 2014) identified 6 additional RR Lyrae with V and I magnitudes appropriate for cluster membership and located beyond 2 arcminutes and within 4 arcminutes of the cluster centre. Arellano Ferro et al. (2023) listed them as OG1-6 and determined that none of them were cluster members. OGLE-BLG-RRLYR-11972 = V1416 Sgr = Gaposchkin #46 OGLE-BLG-RRLYR-11993 = V1418 Sgr = Gaposchkin #50 OGLE-BLG-RRLYR-12032 = V1426 Sgr = Gaposchkin #45 OGLE-BLG-RRLYR-12044 = V1427 Sgr = Gaposchkin #51 OGLE-BLG-RRLYR-12185 OGLE-BLG-RRLYR-33568 -------------------------------------------------------- PSR: According to Paulo Freire's website (July 2024 version) at the Max Planck Institute in Bonn, there are 6 millisecond pulsars in NGC 6522. ================================================================== References Arellano Ferro, A., Prudil, Z., Yepez, M. A., Bustos Fierro, Luna, A. 2023, AP&SS, 368, 91 = arXiv:2310.16257v1 Baade, W. 1946, PASP, 58, 249 Baade, W. 1951, Pub. Obs. Univ. of Michigan, 10, 7 Blanco, B. M. 1984, AJ, 89, 1836 Clube, S. V. M. 1965, RGO Bull. 95, E383 Gaia Collaboration, Vallenari, A., Brown, A. G. A., Prusti, T. et al. 2023, A&A, 674, 1 Gaposchkin, S. I. 1955, Per. Zvez., 10, 337 Gaposchkin, S. I. 1956, Per. Zvez., 11, 268 Harris, W. E. 1996, AJ, 112, 1487 McNamara, D. H., Madsen, J. B., Barnes, J., Ericksen, B. F. 2000, PASP, 112, 202 Prudil Z., Arellano Ferro, A. 2024, MNRAS, 534, 3654 Sawyer, H. B. 1955, Publ. DDO, 2, No. 2 Sawyer Hogg, H. 1973, Publ. DDO, 3, No. 6 Soszynski, I., Dziembowski, W. A., Udalski, A., Poleski, R., Szymanski, M. K., Kubiak, M., Pietrzynski, G. and 4 coauthors, 2011a, Ac. A., 61, 1 Soszynski, I., Udalski, A., Pietrukowicz, P., Szymanski, M. K., Kubiak, M., Pietrzynski, G. , Wyrzykowski, L. and 3 coauthors, 2011b, Ac. A., 61, 285 Soszynski, I., Udalski, A., Szymanski, M. K., Kubiak, M., Pietrzynski, G., Wyrzykowski, L., Ulaczyk, R. and 4 coauthors, 2013, Ac. A. 63, 21 Soszynski, I., Udalski, A., Szymanski, M. K., Pietrukowicz, P., Mroz, P., Skowron, J., Kozlowski, S. and 6 coauthors, 2014, Ac. A. 64, 177 Udalski, A., Kubiak, M., Szymanski, M., Kaluzny, J., Mateo, M., Krzeminski, W. 1994, Ac. A., 44, 317 Walker, A. R. & Mack, P. 1986, MNRAS, 220, 69 ===============================================================