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

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