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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: SAO RAS optical observations
  2. GRB 260604C: GRANDMA observations
  3. GRB 260604B: SVOM/GRM detection
  4. GRB 260605A: Insight-HXMT/HE detection
  5. GRB260603A: SVOM/ECLAIRs refined analysis
  6. EP260605a: Einstein Probe detection of a fast X-ray transient
  7. EP260603a: COLIBRÍ optical upper limit
  8. GRB 260604A: Glowbug gamma-ray detection
  9. GRB 260604C: LCO optical upper limit
  10. GRB 260604C: Liverpool Telescope optical detection
  11. The EP-WXT trigger 01709267001 is likely a flaring star
  12. EP260602d: EP-FXT follow-up observation
  13. EP260602c: EP-FXT follow-up observation
  14. GRB 260601B / EP260601a: AstroSat CZTI detection
  15. GRB 260527A/EP260527a: 6 GHz VLA observations
  16. GRB 260604C: GOTO detections of the optical afterglow
  17. GRB 260604C: Correction to GCN 44828
  18. GRB 260604C: Kilonova-Catcher optical afterglow detection
  19. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  20. The EP-WXT trigger 01709266798 is likely a flaring star
  21. GRB 260604C: Jinshan optical observations
  22. GRB 260604C: Fermi GBM Observation
  23. EP260602d: J-band upper limit with WINTER
  24. EP260602b: J-band upper limit with WINTER
  25. GRB 260604C: LAST detection of optical counterpart candidate
  26. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  27. Fermi GRB 260604C: Global MASTER-Net observations report
  28. Fermi GRB 260604C: Global MASTER-Net observations report
  29. SVOM GRB260604.85: Global MASTER-Net observations report
  30. GRB 260604C: SVOM detection of a long burst
  31. GRB 260604C: Fermi GBM Final Real-time Localization
  32. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  33. GRB 260603A: NOT optical observations
  34. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  35. GRB 260604B: Fermi GBM Final Real-time Localization
  36. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  37. EP260602a: EP-FXT follow-up observation
  38. EP260603a: Global MASTER-Net observations report
  39. EP260603a: Einstein Probe detection of a fast X-ray transient
  40. EP260602d: Optical Upper limits with kinder observations
  41. GRB 260604A: Fermi GBM Final Real-time Localization
  42. EP260602b: Liverpool Telescope observations
  43. EP260602a: Liverpool Telescope optical upper limits
  44. EP260602b: Liverpool Telescope and LCO observations
  45. GRB 260603B: Fermi GBM Final Localization
  46. EP260602a: GTC and Liverpool Telescope optical observations
  47. Konus-Wind detection of GRB 260601B/EP260601a
  48. GRB 260603A: EP-FXT follow-up observation
  49. EP260601a/GRB 260601B: EP-FXT follow-up observation
  50. GRB 260601B / EP260601a: Mondy optical upper limit
  51. EP260602b: EP-FXT follow-up observation
  52. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  53. GRB 260603A: Kilonova-Catcher optical upper limit
  54. GRB 260603A: SVOM/VT optical observations
  55. EP260602a: NOT NIR J-band observations
  56. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  57. EP260602d: Einstein Probe detection of a fast X-ray transient
  58. Fermi trigger No 802141998: Global MASTER-Net observations report
  59. EP260602a: SVOM/VT optical magnitudes correction
  60. GRB 260601A: SVOM/GRM observation of a short burst
  61. EP260602c: Einstein Probe detection of a fast X-ray transient
  62. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  63. EP260602a: COLIBRÍ optical observations
  64. GRB260601B/EP260601a: NOT near-infrared observations
  65. SVOM GRB260603.23: Global MASTER-Net observations report
  66. GRB 260603A: SVOM detection of a burst
  67. EP260602b: Einstein Probe detection of a fast X-ray transient
  68. GRB 260601B/EP260601a: Insight-HXMT detection
  69. Fermi GRB 260602B: Global MASTER-Net observations report
  70. Fermi GRB 260602B: Global MASTER-Net observations report
  71. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  72. EP260602a: SVOM/VT optical candidate
  73. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  74. GRB 260602B: Fermi GBM Final Localization
  75. GRB 260601A: GECAM-B observation of a short burst
  76. GRB 260601B/EP260601a: J-band upper limit with WINTER
  77. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  78. EP260530a/AT 2026nwl: KAIT optical observations
  79. GRB 260602A: Fermi GBM Final Real-time Localization
  80. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  81. EP260602a: Optical upper limits with Kinder observations
  82. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  83. EP260602a: Einstein Probe detection of a fast X-ray transient
  84. GRB 260601B/EP260601a: SVOM/VT optical observations
  85. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  86. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  87. EP260601a: Einstein Probe detection of an X-ray transient
  88. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  89. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  90. GRB 260601A: Glowbug gamma-ray detection of a short burst
  91. GRB 260531B: Glowbug gamma-ray detection
  92. GRB 260516D: VLA radio detection
  93. GRB 260601A: Fermi GBM Observation
  94. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  95. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  96. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  97. Fermi GRB 260601A: Global MASTER-Net observations report
  98. GRB 260601A: Fermi GBM Final Real-time Localization
  99. GRB 260531B: GECAM-B observation
  100. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp

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