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

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