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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. GRB260603A: SVOM/ECLAIRs refined analysis
  2. EP260605a: Einstein Probe detection of a fast X-ray transient
  3. EP260603a: COLIBRÍ optical upper limit
  4. GRB 260604A: Glowbug gamma-ray detection
  5. GRB 260604C: LCO optical upper limit
  6. GRB 260604C: Liverpool Telescope optical detection
  7. The EP-WXT trigger 01709267001 is likely a flaring star
  8. EP260602d: EP-FXT follow-up observation
  9. EP260602c: EP-FXT follow-up observation
  10. GRB 260601B / EP260601a: AstroSat CZTI detection
  11. GRB 260527A/EP260527a: 6 GHz VLA observations
  12. GRB 260604C: GOTO detections of the optical afterglow
  13. GRB 260604C: Correction to GCN 44828
  14. GRB 260604C: Kilonova-Catcher optical afterglow detection
  15. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  16. The EP-WXT trigger 01709266798 is likely a flaring star
  17. GRB 260604C: Jinshan optical observations
  18. GRB 260604C: Fermi GBM Observation
  19. EP260602d: J-band upper limit with WINTER
  20. EP260602b: J-band upper limit with WINTER
  21. GRB 260604C: LAST detection of optical counterpart candidate
  22. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  23. Fermi GRB 260604C: Global MASTER-Net observations report
  24. Fermi GRB 260604C: Global MASTER-Net observations report
  25. SVOM GRB260604.85: Global MASTER-Net observations report
  26. GRB 260604C: SVOM detection of a long burst
  27. GRB 260604C: Fermi GBM Final Real-time Localization
  28. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  29. GRB 260603A: NOT optical observations
  30. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  31. GRB 260604B: Fermi GBM Final Real-time Localization
  32. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  33. EP260602a: EP-FXT follow-up observation
  34. EP260603a: Global MASTER-Net observations report
  35. EP260603a: Einstein Probe detection of a fast X-ray transient
  36. EP260602d: Optical Upper limits with kinder observations
  37. GRB 260604A: Fermi GBM Final Real-time Localization
  38. EP260602b: Liverpool Telescope observations
  39. EP260602a: Liverpool Telescope optical upper limits
  40. EP260602b: Liverpool Telescope and LCO observations
  41. GRB 260603B: Fermi GBM Final Localization
  42. EP260602a: GTC and Liverpool Telescope optical observations
  43. Konus-Wind detection of GRB 260601B/EP260601a
  44. GRB 260603A: EP-FXT follow-up observation
  45. EP260601a/GRB 260601B: EP-FXT follow-up observation
  46. GRB 260601B / EP260601a: Mondy optical upper limit
  47. EP260602b: EP-FXT follow-up observation
  48. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  49. GRB 260603A: Kilonova-Catcher optical upper limit
  50. GRB 260603A: SVOM/VT optical observations
  51. EP260602a: NOT NIR J-band observations
  52. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  53. EP260602d: Einstein Probe detection of a fast X-ray transient
  54. Fermi trigger No 802141998: Global MASTER-Net observations report
  55. EP260602a: SVOM/VT optical magnitudes correction
  56. GRB 260601A: SVOM/GRM observation of a short burst
  57. EP260602c: Einstein Probe detection of a fast X-ray transient
  58. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  59. EP260602a: COLIBRÍ optical observations
  60. GRB260601B/EP260601a: NOT near-infrared observations
  61. SVOM GRB260603.23: Global MASTER-Net observations report
  62. GRB 260603A: SVOM detection of a burst
  63. EP260602b: Einstein Probe detection of a fast X-ray transient
  64. GRB 260601B/EP260601a: Insight-HXMT detection
  65. Fermi GRB 260602B: Global MASTER-Net observations report
  66. Fermi GRB 260602B: Global MASTER-Net observations report
  67. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  68. EP260602a: SVOM/VT optical candidate
  69. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  70. GRB 260602B: Fermi GBM Final Localization
  71. GRB 260601A: GECAM-B observation of a short burst
  72. GRB 260601B/EP260601a: J-band upper limit with WINTER
  73. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  74. EP260530a/AT 2026nwl: KAIT optical observations
  75. GRB 260602A: Fermi GBM Final Real-time Localization
  76. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  77. EP260602a: Optical upper limits with Kinder observations
  78. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  79. EP260602a: Einstein Probe detection of a fast X-ray transient
  80. GRB 260601B/EP260601a: SVOM/VT optical observations
  81. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  82. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  83. EP260601a: Einstein Probe detection of an X-ray transient
  84. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  85. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  86. GRB 260601A: Glowbug gamma-ray detection of a short burst
  87. GRB 260531B: Glowbug gamma-ray detection
  88. GRB 260516D: VLA radio detection
  89. GRB 260601A: Fermi GBM Observation
  90. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  91. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  92. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  93. Fermi GRB 260601A: Global MASTER-Net observations report
  94. GRB 260601A: Fermi GBM Final Real-time Localization
  95. GRB 260531B: GECAM-B observation
  96. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  97. The EP-WXT trigger 01709266272 is likely a flaring star
  98. GRB 260531C: Fermi GBM Final Localization Correction
  99. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  100. AT2026nik: EP-FXT X-ray counterpart

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