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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 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  2. GRB 260607A: Fermi GBM Final Real-time Localization
  3. GRB 260604C: GECAM-B observation
  4. GRB 260604C: 6 GHz VLA observations
  5. GRB 260604C: SAO RAS optical observations
  6. GRB 260604C: GRANDMA observations
  7. GRB 260604B: SVOM/GRM detection
  8. GRB 260605A: Insight-HXMT/HE detection
  9. GRB260603A: SVOM/ECLAIRs refined analysis
  10. EP260605a: Einstein Probe detection of a fast X-ray transient
  11. EP260603a: COLIBRÍ optical upper limit
  12. GRB 260604A: Glowbug gamma-ray detection
  13. GRB 260604C: LCO optical upper limit
  14. GRB 260604C: Liverpool Telescope optical detection
  15. The EP-WXT trigger 01709267001 is likely a flaring star
  16. EP260602d: EP-FXT follow-up observation
  17. EP260602c: EP-FXT follow-up observation
  18. GRB 260601B / EP260601a: AstroSat CZTI detection
  19. GRB 260527A/EP260527a: 6 GHz VLA observations
  20. GRB 260604C: GOTO detections of the optical afterglow
  21. GRB 260604C: Correction to GCN 44828
  22. GRB 260604C: Kilonova-Catcher optical afterglow detection
  23. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  24. The EP-WXT trigger 01709266798 is likely a flaring star
  25. GRB 260604C: Jinshan optical observations
  26. GRB 260604C: Fermi GBM Observation
  27. EP260602d: J-band upper limit with WINTER
  28. EP260602b: J-band upper limit with WINTER
  29. GRB 260604C: LAST detection of optical counterpart candidate
  30. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  31. Fermi GRB 260604C: Global MASTER-Net observations report
  32. Fermi GRB 260604C: Global MASTER-Net observations report
  33. SVOM GRB260604.85: Global MASTER-Net observations report
  34. GRB 260604C: SVOM detection of a long burst
  35. GRB 260604C: Fermi GBM Final Real-time Localization
  36. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  37. GRB 260603A: NOT optical observations
  38. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  39. GRB 260604B: Fermi GBM Final Real-time Localization
  40. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  41. EP260602a: EP-FXT follow-up observation
  42. EP260603a: Global MASTER-Net observations report
  43. EP260603a: Einstein Probe detection of a fast X-ray transient
  44. EP260602d: Optical Upper limits with kinder observations
  45. GRB 260604A: Fermi GBM Final Real-time Localization
  46. EP260602b: Liverpool Telescope observations
  47. EP260602a: Liverpool Telescope optical upper limits
  48. EP260602b: Liverpool Telescope and LCO observations
  49. GRB 260603B: Fermi GBM Final Localization
  50. EP260602a: GTC and Liverpool Telescope optical observations
  51. Konus-Wind detection of GRB 260601B/EP260601a
  52. GRB 260603A: EP-FXT follow-up observation
  53. EP260601a/GRB 260601B: EP-FXT follow-up observation
  54. GRB 260601B / EP260601a: Mondy optical upper limit
  55. EP260602b: EP-FXT follow-up observation
  56. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  57. GRB 260603A: Kilonova-Catcher optical upper limit
  58. GRB 260603A: SVOM/VT optical observations
  59. EP260602a: NOT NIR J-band observations
  60. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  61. EP260602d: Einstein Probe detection of a fast X-ray transient
  62. Fermi trigger No 802141998: Global MASTER-Net observations report
  63. EP260602a: SVOM/VT optical magnitudes correction
  64. GRB 260601A: SVOM/GRM observation of a short burst
  65. EP260602c: Einstein Probe detection of a fast X-ray transient
  66. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  67. EP260602a: COLIBRÍ optical observations
  68. GRB260601B/EP260601a: NOT near-infrared observations
  69. SVOM GRB260603.23: Global MASTER-Net observations report
  70. GRB 260603A: SVOM detection of a burst
  71. EP260602b: Einstein Probe detection of a fast X-ray transient
  72. GRB 260601B/EP260601a: Insight-HXMT detection
  73. Fermi GRB 260602B: Global MASTER-Net observations report
  74. Fermi GRB 260602B: Global MASTER-Net observations report
  75. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  76. EP260602a: SVOM/VT optical candidate
  77. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  78. GRB 260602B: Fermi GBM Final Localization
  79. GRB 260601A: GECAM-B observation of a short burst
  80. GRB 260601B/EP260601a: J-band upper limit with WINTER
  81. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  82. EP260530a/AT 2026nwl: KAIT optical observations
  83. GRB 260602A: Fermi GBM Final Real-time Localization
  84. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  85. EP260602a: Optical upper limits with Kinder observations
  86. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  87. EP260602a: Einstein Probe detection of a fast X-ray transient
  88. GRB 260601B/EP260601a: SVOM/VT optical observations
  89. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  90. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  91. EP260601a: Einstein Probe detection of an X-ray transient
  92. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  93. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  94. GRB 260601A: Glowbug gamma-ray detection of a short burst
  95. GRB 260531B: Glowbug gamma-ray detection
  96. GRB 260516D: VLA radio detection
  97. GRB 260601A: Fermi GBM Observation
  98. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  99. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  100. GRB 260527A/EP260527a: Glowbug gamma-ray detection

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