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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: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  2. GRB 260604A: SVOM/GRM detection
  3. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  4. GRB 260607B: Fermi GBM Observation
  5. GRB 260607B: Fermi-LAT detection
  6. GRB 260607B: Fermi GBM Final Localization Correction
  7. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  8. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  9. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  10. GRB 260607A: Fermi GBM Final Real-time Localization
  11. GRB 260604C: GECAM-B observation
  12. GRB 260604C: 6 GHz VLA observations
  13. GRB 260604C: SAO RAS optical observations
  14. GRB 260604C: GRANDMA observations
  15. GRB 260604B: SVOM/GRM detection
  16. GRB 260605A: Insight-HXMT/HE detection
  17. GRB260603A: SVOM/ECLAIRs refined analysis
  18. EP260605a: Einstein Probe detection of a fast X-ray transient
  19. EP260603a: COLIBRÍ optical upper limit
  20. GRB 260604A: Glowbug gamma-ray detection
  21. GRB 260604C: LCO optical upper limit
  22. GRB 260604C: Liverpool Telescope optical detection
  23. The EP-WXT trigger 01709267001 is likely a flaring star
  24. EP260602d: EP-FXT follow-up observation
  25. EP260602c: EP-FXT follow-up observation
  26. GRB 260601B / EP260601a: AstroSat CZTI detection
  27. GRB 260527A/EP260527a: 6 GHz VLA observations
  28. GRB 260604C: GOTO detections of the optical afterglow
  29. GRB 260604C: Correction to GCN 44828
  30. GRB 260604C: Kilonova-Catcher optical afterglow detection
  31. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  32. The EP-WXT trigger 01709266798 is likely a flaring star
  33. GRB 260604C: Jinshan optical observations
  34. GRB 260604C: Fermi GBM Observation
  35. EP260602d: J-band upper limit with WINTER
  36. EP260602b: J-band upper limit with WINTER
  37. GRB 260604C: LAST detection of optical counterpart candidate
  38. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  39. Fermi GRB 260604C: Global MASTER-Net observations report
  40. Fermi GRB 260604C: Global MASTER-Net observations report
  41. SVOM GRB260604.85: Global MASTER-Net observations report
  42. GRB 260604C: SVOM detection of a long burst
  43. GRB 260604C: Fermi GBM Final Real-time Localization
  44. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  45. GRB 260603A: NOT optical observations
  46. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  47. GRB 260604B: Fermi GBM Final Real-time Localization
  48. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  49. EP260602a: EP-FXT follow-up observation
  50. EP260603a: Global MASTER-Net observations report
  51. EP260603a: Einstein Probe detection of a fast X-ray transient
  52. EP260602d: Optical Upper limits with kinder observations
  53. GRB 260604A: Fermi GBM Final Real-time Localization
  54. EP260602b: Liverpool Telescope observations
  55. EP260602a: Liverpool Telescope optical upper limits
  56. EP260602b: Liverpool Telescope and LCO observations
  57. GRB 260603B: Fermi GBM Final Localization
  58. EP260602a: GTC and Liverpool Telescope optical observations
  59. Konus-Wind detection of GRB 260601B/EP260601a
  60. GRB 260603A: EP-FXT follow-up observation
  61. EP260601a/GRB 260601B: EP-FXT follow-up observation
  62. GRB 260601B / EP260601a: Mondy optical upper limit
  63. EP260602b: EP-FXT follow-up observation
  64. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  65. GRB 260603A: Kilonova-Catcher optical upper limit
  66. GRB 260603A: SVOM/VT optical observations
  67. EP260602a: NOT NIR J-band observations
  68. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  69. EP260602d: Einstein Probe detection of a fast X-ray transient
  70. Fermi trigger No 802141998: Global MASTER-Net observations report
  71. EP260602a: SVOM/VT optical magnitudes correction
  72. GRB 260601A: SVOM/GRM observation of a short burst
  73. EP260602c: Einstein Probe detection of a fast X-ray transient
  74. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  75. EP260602a: COLIBRÍ optical observations
  76. GRB260601B/EP260601a: NOT near-infrared observations
  77. SVOM GRB260603.23: Global MASTER-Net observations report
  78. GRB 260603A: SVOM detection of a burst
  79. EP260602b: Einstein Probe detection of a fast X-ray transient
  80. GRB 260601B/EP260601a: Insight-HXMT detection
  81. Fermi GRB 260602B: Global MASTER-Net observations report
  82. Fermi GRB 260602B: Global MASTER-Net observations report
  83. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  84. EP260602a: SVOM/VT optical candidate
  85. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  86. GRB 260602B: Fermi GBM Final Localization
  87. GRB 260601A: GECAM-B observation of a short burst
  88. GRB 260601B/EP260601a: J-band upper limit with WINTER
  89. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  90. EP260530a/AT 2026nwl: KAIT optical observations
  91. GRB 260602A: Fermi GBM Final Real-time Localization
  92. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  93. EP260602a: Optical upper limits with Kinder observations
  94. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  95. EP260602a: Einstein Probe detection of a fast X-ray transient
  96. GRB 260601B/EP260601a: SVOM/VT optical observations
  97. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  98. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  99. EP260601a: Einstein Probe detection of an X-ray transient
  100. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations

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