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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"

27021 results found.

  1. EP260603a: Global MASTER-Net observations report
  2. EP260603a: Einstein Probe detection of a fast X-ray transient
  3. GRB 260604A: Fermi GBM Final Real-time Localization
  4. EP260602b: Liverpool Telescope observations
  5. EP260602a: Liverpool Telescope optical upper limits
  6. GRB 260603B: Fermi GBM Final Localization
  7. GRB 260603A: EP-FXT follow-up observation
  8. EP260601a/GRB 260601B: EP-FXT follow-up observation
  9. EP260602b: EP-FXT follow-up observation
  10. GRB 260603A: Kilonova-Catcher optical upper limit
  11. GRB 260603A: SVOM/VT optical observations
  12. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  13. EP260602d: Einstein Probe detection of a fast X-ray transient
  14. Fermi trigger No 802141998: Global MASTER-Net observations report
  15. GRB 260601A: SVOM/GRM observation of a short burst
  16. EP260602c: Einstein Probe detection of a fast X-ray transient
  17. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  18. EP260602a: COLIBRÍ optical observations
  19. GRB260601B/EP260601a: NOT near-infrared observations
  20. SVOM GRB260603.23: Global MASTER-Net observations report
  21. GRB 260603A: SVOM detection of a burst
  22. EP260602b: Einstein Probe detection of a fast X-ray transient
  23. Fermi GRB 260602B: Global MASTER-Net observations report
  24. Fermi GRB 260602B: Global MASTER-Net observations report
  25. EP260602a: SVOM/VT optical candidate
  26. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  27. GRB 260602B: Fermi GBM Final Localization
  28. GRB 260601A: GECAM-B observation of a short burst
  29. GRB 260601B/EP260601a: J-band upper limit with WINTER
  30. GRB 260602A: Fermi GBM Final Real-time Localization
  31. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  32. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  33. EP260602a: Einstein Probe detection of a fast X-ray transient
  34. GRB 260601B/EP260601a: SVOM/VT optical observations
  35. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  36. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  37. EP260601a: Einstein Probe detection of an X-ray transient
  38. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  39. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  40. GRB 260601A: Glowbug gamma-ray detection of a short burst
  41. GRB 260516D: VLA radio detection
  42. GRB 260601A: Fermi GBM Observation
  43. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  44. Fermi GRB 260601A: Global MASTER-Net observations report
  45. GRB 260601A: Fermi GBM Final Real-time Localization
  46. GRB 260531B: GECAM-B observation
  47. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  48. The EP-WXT trigger 01709266272 is likely a flaring star
  49. GRB 260531C: Fermi GBM Final Localization Correction
  50. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  51. Fermi trigger No 801900520: Global MASTER-Net observations report
  52. GRB 260531B: Fermi GBM Final Real-time Localization
  53. AT 2026nuz: COLIBRÍ optical observations
  54. IPN triangulation of GRB 260527A / EP260527a
  55. EP260527a/GRB 260527A: further FTW optical and NIR observations
  56. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  57. GRB 260530A: Fermi GBM Final Real-time Localization
  58. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  59. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  60. GRB 260529A: GOTO tentative optical afterglow candidate
  61. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  62. Fermi GRB 260529A: Global MASTER-Net observations report
  63. GRB 260529A: Fermi GBM Final Real-time Localization
  64. EP260526a: SVOM/VT optical upper limits
  65. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  66. EP260527a / GRB 260527A: NOT optical observations
  67. GRB 260527A/EP260527a: FTW optical and NIR observations
  68. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  69. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  70. EP260527a/GRB 260527A: EP-FXT follow-up observation
  71. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  72. GRB 260526A: GECAM-B observation
  73. EP260526a: EP-FXT follow-up observation
  74. EP260527a: SVOM/VT optical observation
  75. EP260527a: COLIBRÍ optical detection
  76. EP260527a: Einstein Probe detection of a fast X-ray transient
  77. The EP-WXT trigger 01709266172 is likely a flaring star
  78. The EP-WXT trigger 01709266147 is likely a flaring star
  79. Fermi trigger No 801580882: Global MASTER-Net observations report
  80. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  81. EP260526a: Einstein Probe detection of a fast X-ray transient
  82. EP260526.405: COLIBRÍ optical upper limits
  83. The EP-WXT trigger 01709266106 is not a real source
  84. Fermi GRB 260526A: Global MASTER-Net observations report
  85. GRB 260526A: Fermi GBM Final Real-time Localization
  86. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  87. EP-WXT 01709266106: NOT optical upper limits
  88. Fermi GRB 260525A: Global MASTER-Net observations report
  89. GRB 260525A: Fermi GBM Final Real-time Localization
  90. GRB 260523B: GECAM-B observation
  91. Fermi GRB 260523A: Global MASTER-Net observations report
  92. GRB 260523B: Fermi GBM Final Real-time Localization
  93. GRB 260523A: Fermi GBM Final Real-time Localization
  94. GRB 260522A: Fermi GBM Observation
  95. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  96. GRB 260522B: Fermi GBM Final Real-time Localization
  97. GRB 260522A: GOTO optical upper limit
  98. Fermi trigger No 801135305: Global MASTER-Net observations report
  99. Fermi GRB 260522A: Global MASTER-Net observations report
  100. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp

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