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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. EP260603a: Global MASTER-Net observations report
  2. EP260603a: Einstein Probe detection of a fast X-ray transient
  3. EP260602d: Optical Upper limits with kinder observations
  4. GRB 260604A: Fermi GBM Final Real-time Localization
  5. EP260602b: Liverpool Telescope observations
  6. EP260602a: Liverpool Telescope optical upper limits
  7. EP260602b: Liverpool Telescope and LCO observations
  8. GRB 260603B: Fermi GBM Final Localization
  9. EP260602a: GTC and Liverpool Telescope optical observations
  10. Konus-Wind detection of GRB 260601B/EP260601a
  11. GRB 260603A: EP-FXT follow-up observation
  12. EP260601a/GRB 260601B: EP-FXT follow-up observation
  13. GRB 260601B / EP260601a: Mondy optical upper limit
  14. EP260602b: EP-FXT follow-up observation
  15. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  16. GRB 260603A: Kilonova-Catcher optical upper limit
  17. GRB 260603A: SVOM/VT optical observations
  18. EP260602a: NOT NIR J-band observations
  19. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  20. EP260602d: Einstein Probe detection of a fast X-ray transient
  21. Fermi trigger No 802141998: Global MASTER-Net observations report
  22. EP260602a: SVOM/VT optical magnitudes correction
  23. GRB 260601A: SVOM/GRM observation of a short burst
  24. EP260602c: Einstein Probe detection of a fast X-ray transient
  25. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  26. EP260602a: COLIBRÍ optical observations
  27. GRB260601B/EP260601a: NOT near-infrared observations
  28. SVOM GRB260603.23: Global MASTER-Net observations report
  29. GRB 260603A: SVOM detection of a burst
  30. EP260602b: Einstein Probe detection of a fast X-ray transient
  31. GRB 260601B/EP260601a: Insight-HXMT detection
  32. Fermi GRB 260602B: Global MASTER-Net observations report
  33. Fermi GRB 260602B: Global MASTER-Net observations report
  34. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  35. EP260602a: SVOM/VT optical candidate
  36. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  37. GRB 260602B: Fermi GBM Final Localization
  38. GRB 260601A: GECAM-B observation of a short burst
  39. GRB 260601B/EP260601a: J-band upper limit with WINTER
  40. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  41. EP260530a/AT 2026nwl: KAIT optical observations
  42. GRB 260602A: Fermi GBM Final Real-time Localization
  43. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  44. EP260602a: Optical upper limits with Kinder observations
  45. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  46. EP260602a: Einstein Probe detection of a fast X-ray transient
  47. GRB 260601B/EP260601a: SVOM/VT optical observations
  48. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  49. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  50. EP260601a: Einstein Probe detection of an X-ray transient
  51. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  52. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  53. GRB 260601A: Glowbug gamma-ray detection of a short burst
  54. GRB 260531B: Glowbug gamma-ray detection
  55. GRB 260516D: VLA radio detection
  56. GRB 260601A: Fermi GBM Observation
  57. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  58. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  59. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  60. Fermi GRB 260601A: Global MASTER-Net observations report
  61. GRB 260601A: Fermi GBM Final Real-time Localization
  62. GRB 260531B: GECAM-B observation
  63. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  64. The EP-WXT trigger 01709266272 is likely a flaring star
  65. GRB 260531C: Fermi GBM Final Localization Correction
  66. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  67. AT2026nik: EP-FXT X-ray counterpart
  68. Fermi trigger No 801900520: Global MASTER-Net observations report
  69. GRB 260531B: Fermi GBM Final Real-time Localization
  70. GRB 260531A: MAXI/GSC detection
  71. AT 2026nuz: COLIBRÍ optical observations
  72. IPN triangulation of GRB 260527A / EP260527a
  73. EP260527a/GRB 260527A: further FTW optical and NIR observations
  74. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  75. GRB 260530A: Fermi GBM Final Real-time Localization
  76. GRB 260527A / EP260527a: VLA radio detection
  77. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  78. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  79. GRB 260529A: GOTO tentative optical afterglow candidate
  80. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  81. GRB 260527A/EP260527a: Insight-HXMT detection
  82. Fermi GRB 260529A: Global MASTER-Net observations report
  83. GRB 260529A: Fermi GBM Final Real-time Localization
  84. EP260526a: SVOM/VT optical upper limits
  85. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  86. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  87. EP260527a / GRB 260527A: NOT optical observations
  88. GRB 260527A/EP260527a: FTW optical and NIR observations
  89. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  90. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  91. EP260527a/GRB 260527A: EP-FXT follow-up observation
  92. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  93. GRB 260526A: GECAM-B observation
  94. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  95. EP260526a: EP-FXT follow-up observation
  96. EP260527a: SVOM/VT optical observation
  97. EP260527a: COLIBRÍ optical detection
  98. EP260527a: Einstein Probe detection of a fast X-ray transient
  99. The EP-WXT trigger 01709266172 is likely a flaring star
  100. The EP-WXT trigger 01709266147 is likely a flaring star

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