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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 260607B: Fermi GBM Final Localization Correction
  2. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  3. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  4. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  5. GRB 260607A: Fermi GBM Final Real-time Localization
  6. GRB 260604C: GECAM-B observation
  7. GRB 260604C: 6 GHz VLA observations
  8. GRB 260504C: SAO RAS optical observations
  9. GRB 260604C: GRANDMA observations
  10. GRB 260604B: SVOM/GRM detection
  11. GRB 260605A: Insight-HXMT/HE detection
  12. GRB260603A: SVOM/ECLAIRs refined analysis
  13. EP260605a: Einstein Probe detection of a fast X-ray transient
  14. EP260603a: COLIBRÍ optical upper limit
  15. GRB 260604A: Glowbug gamma-ray detection
  16. GRB 260604C: LCO optical upper limit
  17. GRB 260604C: Liverpool Telescope optical detection
  18. The EP-WXT trigger 01709267001 is likely a flaring star
  19. EP260602d: EP-FXT follow-up observation
  20. EP260602c: EP-FXT follow-up observation
  21. GRB 260601B / EP260601a: AstroSat CZTI detection
  22. GRB 260527A/EP260527a: 6 GHz VLA observations
  23. GRB 260604C: GOTO detections of the optical afterglow
  24. GRB 260604C: Correction to GCN 44828
  25. GRB 260604C: Kilonova-Catcher optical afterglow detection
  26. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  27. The EP-WXT trigger 01709266798 is likely a flaring star
  28. GRB 260604C: Jinshan optical observations
  29. GRB 260604C: Fermi GBM Observation
  30. EP260602d: J-band upper limit with WINTER
  31. EP260602b: J-band upper limit with WINTER
  32. GRB 260604C: LAST detection of optical counterpart candidate
  33. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  34. Fermi GRB 260604C: Global MASTER-Net observations report
  35. Fermi GRB 260604C: Global MASTER-Net observations report
  36. SVOM GRB260604.85: Global MASTER-Net observations report
  37. GRB 260604C: SVOM detection of a long burst
  38. GRB 260604C: Fermi GBM Final Real-time Localization
  39. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  40. GRB 260603A: NOT optical observations
  41. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  42. GRB 260604B: Fermi GBM Final Real-time Localization
  43. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  44. EP260602a: EP-FXT follow-up observation
  45. EP260603a: Global MASTER-Net observations report
  46. EP260603a: Einstein Probe detection of a fast X-ray transient
  47. EP260602d: Optical Upper limits with kinder observations
  48. GRB 260604A: Fermi GBM Final Real-time Localization
  49. EP260602b: Liverpool Telescope observations
  50. EP260602a: Liverpool Telescope optical upper limits
  51. EP260602b: Liverpool Telescope and LCO observations
  52. GRB 260603B: Fermi GBM Final Localization
  53. EP260602a: GTC and Liverpool Telescope optical observations
  54. Konus-Wind detection of GRB 260601B/EP260601a
  55. GRB 260603A: EP-FXT follow-up observation
  56. EP260601a/GRB 260601B: EP-FXT follow-up observation
  57. GRB 260601B / EP260601a: Mondy optical upper limit
  58. EP260602b: EP-FXT follow-up observation
  59. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  60. GRB 260603A: Kilonova-Catcher optical upper limit
  61. GRB 260603A: SVOM/VT optical observations
  62. EP260602a: NOT NIR J-band observations
  63. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  64. EP260602d: Einstein Probe detection of a fast X-ray transient
  65. Fermi trigger No 802141998: Global MASTER-Net observations report
  66. EP260602a: SVOM/VT optical magnitudes correction
  67. GRB 260601A: SVOM/GRM observation of a short burst
  68. EP260602c: Einstein Probe detection of a fast X-ray transient
  69. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  70. EP260602a: COLIBRÍ optical observations
  71. GRB260601B/EP260601a: NOT near-infrared observations
  72. SVOM GRB260603.23: Global MASTER-Net observations report
  73. GRB 260603A: SVOM detection of a burst
  74. EP260602b: Einstein Probe detection of a fast X-ray transient
  75. GRB 260601B/EP260601a: Insight-HXMT detection
  76. Fermi GRB 260602B: Global MASTER-Net observations report
  77. Fermi GRB 260602B: Global MASTER-Net observations report
  78. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  79. EP260602a: SVOM/VT optical candidate
  80. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  81. GRB 260602B: Fermi GBM Final Localization
  82. GRB 260601A: GECAM-B observation of a short burst
  83. GRB 260601B/EP260601a: J-band upper limit with WINTER
  84. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  85. EP260530a/AT 2026nwl: KAIT optical observations
  86. GRB 260602A: Fermi GBM Final Real-time Localization
  87. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  88. EP260602a: Optical upper limits with Kinder observations
  89. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  90. EP260602a: Einstein Probe detection of a fast X-ray transient
  91. GRB 260601B/EP260601a: SVOM/VT optical observations
  92. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  93. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  94. EP260601a: Einstein Probe detection of an X-ray transient
  95. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  96. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  97. GRB 260601A: Glowbug gamma-ray detection of a short burst
  98. GRB 260531B: Glowbug gamma-ray detection
  99. GRB 260516D: VLA radio detection
  100. GRB 260601A: Fermi GBM Observation

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