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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 260302A: Fermi GBM Final Real-time Localization
  2. EP260227a: Mondy optical observations
  3. GRB 260228A: CAHA 2.2m telescope optical upper limit
  4. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  5. EP260227a: Mephisto optical detection
  6. GRID detection of GRB 260225D
  7. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  8. EP260227a: further LCO observations
  9. EP260227a: SVOM/VT optical observation
  10. GRB 260228A: SVOM/VT optical upper limits
  11. GRB 260225D: SVOM/GRM observation
  12. EP260227A: 3.6m DOT optical afterglow detection
  13. GRB 260225B: SVOM/GRM observation
  14. GRB 260228A: SVOM detection of a burst
  15. EP260227a: FTW optical and NIR observations
  16. EP260227a: Liverpool Telescope optical observations
  17. EP260227a: LCOGT Optical Observations
  18. GRB 260226A: Asiago r-band upper limit
  19. EP260227a: Thai National Telescope observations
  20. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  21. EP260227a: Liverpool Telescope observations
  22. EP260227a: COLIBRÍ optical observations
  23. EP260227a: NOT optical observations
  24. GRB 260225A: SVOM/VT optical continued observations and upper limit
  25. GRID detection of GRB 260223A
  26. EP260227a: Global MASTER-Net observations report
  27. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  28. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  29. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  30. IceCube cascade alert 142200_1517143 retraction
  31. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  32. Konus-Wind detection of GRB 260226A
  33. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  34. EP260214a: VLT/FORS2 optical observations
  35. GRB 260225A: WINTER J-band upper limit
  36. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  37. GRB 260226A: COLIBRÍ optical upper limits
  38. GRB 260226A: LCOGT Optical Upper Limit
  39. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  40. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  41. GRB 260226A: Glowbug gamma-ray detection
  42. GRB 260226A: NuSTAR detection of bright prompt emission
  43. GRB 260226A : GROWTH-India Telescope optical observations
  44. GRB 260226A: LAST optical upper limit
  45. GRB 260226A: Fermi GBM observation
  46. GRB 260226A: Fermi-LAT refined analysis
  47. The EP-WXT trigger 01709258652 is likely a flaring star
  48. LAT GRB260226.44: Global MASTER-Net observations report
  49. Fermi GRB 260226A: Global MASTER-Net observations report
  50. GRB 260226A: AstroSat CZTI detection of bright long burst
  51. EP260214a: VLA 6 GHz detection
  52. GRB 260226A: Fermi-LAT detection of a bright burst
  53. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  54. EP260224a: LCO optical upper limits
  55. GRB260225A: SVOM/ECLAIRs refined position
  56. GRB 260226A: Fermi GBM Final Real-time Localization
  57. GRB 260225A: EP-FXT follow-up observation
  58. GRB 260225A: SVOM/VT optical observation
  59. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  60. GRB 260225C: Fermi GBM Final Real-time Localization
  61. GRB 260223A: Fermi GBM Observation
  62. GRB 260225A: SVOM/VT optical upper limits
  63. GRB 260225B: Fermi GBM Final Real-time Localization
  64. EP260126a: VLA 6 GHz detection
  65. EP260223a: Liverpool Telescope upper limits
  66. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  67. GRB 260225A: SVOM detection of a burst
  68. EP260224a: Einstein Probe detection of an X-ray transient
  69. EP 260225.148: COLIBRÍ Confirmation of flaring star
  70. EP260223a: Xinglong optical upper limit
  71. The EP-WXT trigger 01709258631 is likely a flaring star
  72. GRB 260223A: Glowbug gamma-ray detection
  73. EP260213a: Mephisto optical upper limits
  74. EP260223a: EP-FXT follow-up observation
  75. sb26021801: SVOM/VT optical upper limits
  76. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  77. sb26021801: SVOM/C-GFT upper limit
  78. EP260223a: COLIBRÍ optical upper limits
  79. EP260223a: Einstein Probe detection of an X-ray transient
  80. GRB 260223A: SVOM/VT optical observation
  81. GRB 260223A: SVOM/GRM observation
  82. GRB 260223A: COLIBRÍ further optical observations and a brightening
  83. EP260221a: Optical upper limit with Kinder observations
  84. GRB 260223A: COLIBRÍ optical observations
  85. GRB 260223A: DDOTI Optical Candidate
  86. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  87. Fermi GRB 260223A: Global MASTER-Net observations report
  88. GRB 260223A: Fermi GBM Final Real-time Localization
  89. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  90. EP260221a: COLIBRÍ optical counterpart candidate
  91. EP260221a: Gemini South z-band upper limit
  92. GRB 260222A: Fermi GBM Final Real-time Localization
  93. EP260221a: Global MASTER-Net observations report
  94. EP260221a: EP-FXT follow-up observation
  95. Fermi GRB 260221B: Global MASTER-Net observations report
  96. GRB 260221B: Fermi GBM Final Real-time Localization
  97. EP-WXT01709258519: Xinglong optical upper limit
  98. EP260221a: Xinglong optical upper limit
  99. Fermi GRB 260221A: Global MASTER-Net observations report
  100. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations

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