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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"

39220 results found.

  1. EP260601a/GRB 260601B: EP-FXT follow-up observation
  2. GRB 260601B / EP260601a: Mondy optical upper limit
  3. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  4. GRB 260603A: Kilonova-Catcher optical upper limit
  5. GRB 260603A: SVOM/VT optical observations
  6. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  7. Fermi trigger No 802141998: Global MASTER-Net observations report
  8. GRB 260601A: SVOM/GRM observation of a short burst
  9. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  10. EP260602a: COLIBRÍ optical observations
  11. SVOM GRB260603.23: Global MASTER-Net observations report
  12. GRB 260603A: SVOM detection of a burst
  13. GRB 260601B/EP260601a: Insight-HXMT detection
  14. Fermi GRB 260602B: Global MASTER-Net observations report
  15. Fermi GRB 260602B: Global MASTER-Net observations report
  16. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  17. GRB 260602B: Fermi GBM Final Localization
  18. GRB 260601A: GECAM-B observation of a short burst
  19. GRB 260601B/EP260601a: J-band upper limit with WINTER
  20. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  21. EP260530a/AT 2026nwl: KAIT optical observations
  22. GRB 260602A: Fermi GBM Final Real-time Localization
  23. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  24. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  25. GRB 260601B/EP260601a: SVOM/VT optical observations
  26. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  27. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  28. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  29. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  30. GRB 260601A: Glowbug gamma-ray detection of a short burst
  31. GRB 260531B: Glowbug gamma-ray detection
  32. GRB 260516D: VLA radio detection
  33. GRB 260601A: Fermi GBM Observation
  34. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  35. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  36. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  37. Fermi GRB 260601A: Global MASTER-Net observations report
  38. GRB 260601A: Fermi GBM Final Real-time Localization
  39. GRB 260531B: GECAM-B observation
  40. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  41. GRB 260531C: Fermi GBM Final Localization Correction
  42. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  43. Fermi trigger No 801900520: Global MASTER-Net observations report
  44. GRB 260531B: Fermi GBM Final Real-time Localization
  45. GRB 260531A: MAXI/GSC detection
  46. AT 2026nuz: COLIBRÍ optical observations
  47. IPN triangulation of GRB 260527A / EP260527a
  48. EP260527a/GRB 260527A: further FTW optical and NIR observations
  49. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  50. GRB 260530A: Fermi GBM Final Real-time Localization
  51. GRB 260527A / EP260527a: VLA radio detection
  52. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  53. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  54. GRB 260529A: GOTO tentative optical afterglow candidate
  55. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  56. GRB 260527A/EP260527a: Insight-HXMT detection
  57. Fermi GRB 260529A: Global MASTER-Net observations report
  58. GRB 260529A: Fermi GBM Final Real-time Localization
  59. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  60. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  61. EP260527a / GRB 260527A: NOT optical observations
  62. GRB 260527A/EP260527a: FTW optical and NIR observations
  63. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  64. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  65. EP260527a/GRB 260527A: EP-FXT follow-up observation
  66. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  67. GRB 260526A: GECAM-B observation
  68. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  69. EP260527a: COLIBRÍ optical detection
  70. Fermi trigger No 801580882: Global MASTER-Net observations report
  71. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  72. EP260526a: LCO optical upper limits
  73. GRB 260525A: AstroSat CZTI detection
  74. EP260526.405: COLIBRÍ optical upper limits
  75. Fermi GRB 260526A: Global MASTER-Net observations report
  76. GRB 260526A: Fermi GBM Final Real-time Localization
  77. Fermi GRB 260525A: Global MASTER-Net observations report
  78. GRB 260525A: Fermi GBM Final Real-time Localization
  79. GRB 260523B: AstroSat CZTI detection
  80. GRB 260523B: GECAM-B observation
  81. Fermi GRB 260523A: Global MASTER-Net observations report
  82. GRB 260523B: Fermi GBM Final Real-time Localization
  83. GRB 260523A: Fermi GBM Final Real-time Localization
  84. GRB 260522A: Fermi GBM Observation
  85. GRB 260522B: NuSTAR detection of prompt emission
  86. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  87. GRB 260522B: Fermi GBM Final Real-time Localization
  88. GRB 260522A: GOTO optical upper limit
  89. Fermi trigger No 801135305: Global MASTER-Net observations report
  90. Fermi GRB 260522A: Global MASTER-Net observations report
  91. GRB 260522A: Fermi-LAT detection
  92. GRB 260519C: SVOM/GRM observation
  93. GRB 260522A: Fermi GBM Final Real-time Localization
  94. GRB 260511A: iTelescope T-75 optical detection
  95. GRB 260520B: SVOM/GRM observation
  96. GRB 260411B: TERI Gamma-ray detection
  97. GRB 260407A: TERI Gamma-ray detection
  98. GRB 260307A: TERI Gamma-ray detection
  99. GRB 260225D: TERI Gamma-ray detection
  100. GRB 251118A: TERI Gamma-ray detection

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