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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"

27400 results found.

  1. EP260602c: Einstein Probe detection of a fast X-ray transient
  2. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  3. EP260602a: COLIBRÍ optical observations
  4. GRB260601B/EP260601a: NOT near-infrared observations
  5. SVOM GRB260603.23: Global MASTER-Net observations report
  6. GRB 260603A: SVOM detection of a burst
  7. Fermi GRB 260602B: Global MASTER-Net observations report
  8. Fermi GRB 260602B: Global MASTER-Net observations report
  9. EP260602a: SVOM/VT optical candidate
  10. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  11. GRB 260602B: Fermi GBM Final Localization
  12. GRB 260601B/EP260601a: J-band upper limit with WINTER
  13. GRB 260602A: Fermi GBM Final Real-time Localization
  14. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  15. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  16. GRB 260601B/EP260601a: SVOM/VT optical observations
  17. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  18. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  19. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  20. GRB 260601A: Glowbug gamma-ray detection of a short burst
  21. GRB 260516D: VLA radio detection
  22. GRB 260601A: Fermi GBM Observation
  23. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  24. Fermi GRB 260601A: Global MASTER-Net observations report
  25. GRB 260601A: Fermi GBM Final Real-time Localization
  26. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  27. The EP-WXT trigger 01709266272 is likely a flaring star
  28. GRB 260531C: Fermi GBM Final Localization Correction
  29. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  30. Fermi trigger No 801900520: Global MASTER-Net observations report
  31. GRB 260531B: Fermi GBM Final Real-time Localization
  32. AT 2026nuz: COLIBRÍ optical observations
  33. IPN triangulation of GRB 260527A / EP260527a
  34. EP260527a/GRB 260527A: further FTW optical and NIR observations
  35. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  36. GRB 260530A: Fermi GBM Final Real-time Localization
  37. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  38. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  39. GRB 260529A: GOTO tentative optical afterglow candidate
  40. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  41. Fermi GRB 260529A: Global MASTER-Net observations report
  42. GRB 260529A: Fermi GBM Final Real-time Localization
  43. EP260526a: SVOM/VT optical upper limits
  44. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  45. EP260527a / GRB 260527A: NOT optical observations
  46. GRB 260527A/EP260527a: FTW optical and NIR observations
  47. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  48. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  49. EP260527a: SVOM/VT optical observation
  50. EP260527a: COLIBRÍ optical detection
  51. EP260527a: Einstein Probe detection of a fast X-ray transient
  52. The EP-WXT trigger 01709266172 is likely a flaring star
  53. The EP-WXT trigger 01709266147 is likely a flaring star
  54. Fermi trigger No 801580882: Global MASTER-Net observations report
  55. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  56. EP260526a: Einstein Probe detection of a fast X-ray transient
  57. EP260526.405: COLIBRÍ optical upper limits
  58. The EP-WXT trigger 01709266106 is not a real source
  59. Fermi GRB 260526A: Global MASTER-Net observations report
  60. GRB 260526A: Fermi GBM Final Real-time Localization
  61. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  62. EP-WXT 01709266106: NOT optical upper limits
  63. Fermi GRB 260525A: Global MASTER-Net observations report
  64. GRB 260525A: Fermi GBM Final Real-time Localization
  65. Fermi GRB 260523A: Global MASTER-Net observations report
  66. GRB 260523B: Fermi GBM Final Real-time Localization
  67. GRB 260523A: Fermi GBM Final Real-time Localization
  68. GRB 260522A: Fermi GBM Observation
  69. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  70. GRB 260522B: Fermi GBM Final Real-time Localization
  71. GRB 260522A: GOTO optical upper limit
  72. Fermi trigger No 801135305: Global MASTER-Net observations report
  73. Fermi GRB 260522A: Global MASTER-Net observations report
  74. GRB 260522A: Fermi-LAT detection
  75. GRB 260519C: SVOM/GRM observation
  76. GRB 260522A: Fermi GBM Final Real-time Localization
  77. GRB 260511A: iTelescope T-75 optical detection
  78. GRB 260520B: Fermi GBM Final Localization
  79. GRB 260520A: Fermi GBM Final Localization
  80. GRB 260519D: Fermi GBM Final Localization Correction
  81. GRB 260519B: Fermi GBM Final Localization
  82. GRB 260519A: Fermi GBM Final Localization
  83. GRB 260516D: SVOM/ECLAIRs refined analysis
  84. GRB 260515A: SVOM/ECLAIRs refined analysis
  85. GRB 260509A: CrAO ZTSh optical upper limit
  86. GRB 260516D: EP-FXT follow-up observation
  87. GRB 260516D: LCO optical observations
  88. GRB 260515A: further Liverpool Telescope observations
  89. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  91. GRB 260516D: GROWTH-India Telescope optical detection
  92. GRB 260516D: SVOM/VT optical bright candidate
  93. GRB 260516D: FRAM-ORM optical limit
  94. GRB 260515A: CrAO ZTSh BVRI optical observations
  95. Fermi GRB 260516C: Global MASTER-Net observations report
  96. SVOM GRB260516D: Global MASTER-Net observations report
  97. GRB 260516D: SVOM possible detection of a burst
  98. GRB 260516C: Fermi GBM Final Real-time Localization
  99. GRB 260515A: LCO optical counterpart detection
  100. Fermi Gamma-ray Burst Monitor trigger 800627191/260516518 is not a GRB

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