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

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