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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"

45651 results found.

  1. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  2. EP260602a: Optical upper limits with Kinder observations
  3. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  4. EP260602a: Einstein Probe detection of a fast X-ray transient
  5. GRB 260601B/EP260601a: SVOM/VT optical observations
  6. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  7. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  8. EP260601a: Einstein Probe detection of an X-ray transient
  9. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  10. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  11. GRB 260601A: Glowbug gamma-ray detection of a short burst
  12. GRB 260531B: Glowbug gamma-ray detection
  13. GRB 260516D: VLA radio detection
  14. GRB 260601A: Fermi GBM Observation
  15. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  16. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  17. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  18. Fermi GRB 260601A: Global MASTER-Net observations report
  19. GRB 260601A: Fermi GBM Final Real-time Localization
  20. GRB 260531B: GECAM-B observation
  21. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  22. The EP-WXT trigger 01709266272 is likely a flaring star
  23. GRB 260531C: Fermi GBM Final Localization Correction
  24. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  25. AT2026nik: EP-FXT X-ray counterpart
  26. Fermi trigger No 801900520: Global MASTER-Net observations report
  27. GRB 260531B: Fermi GBM Final Real-time Localization
  28. GRB 260531A: MAXI/GSC detection
  29. AT 2026nuz: COLIBRÍ optical observations
  30. IPN triangulation of GRB 260527A / EP260527a
  31. EP260527a/GRB 260527A: further FTW optical and NIR observations
  32. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  33. GRB 260530A: Fermi GBM Final Real-time Localization
  34. GRB 260527A / EP260527a: VLA radio detection
  35. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  36. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  37. GRB 260529A: GOTO tentative optical afterglow candidate
  38. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  39. GRB 260527A/EP260527a: Insight-HXMT detection
  40. Fermi GRB 260529A: Global MASTER-Net observations report
  41. GRB 260529A: Fermi GBM Final Real-time Localization
  42. EP260526a: SVOM/VT optical upper limits
  43. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  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/GRB 260527A: EP-FXT follow-up observation
  50. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  51. GRB 260526A: GECAM-B observation
  52. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  53. EP260526a: EP-FXT follow-up observation
  54. EP260527a: SVOM/VT optical observation
  55. EP260527a: COLIBRÍ optical detection
  56. EP260527a: Einstein Probe detection of a fast X-ray transient
  57. The EP-WXT trigger 01709266172 is likely a flaring star
  58. The EP-WXT trigger 01709266147 is likely a flaring star
  59. Fermi trigger No 801580882: Global MASTER-Net observations report
  60. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  61. EP260526a: LCO optical upper limits
  62. EP260526a: Einstein Probe detection of a fast X-ray transient
  63. GRB 260525A: AstroSat CZTI detection
  64. EP260526.405: COLIBRÍ optical upper limits
  65. The EP-WXT trigger 01709266106 is not a real source
  66. Fermi GRB 260526A: Global MASTER-Net observations report
  67. GRB 260526A: Fermi GBM Final Real-time Localization
  68. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  69. EP-WXT 01709266106: NOT optical upper limits
  70. Fermi GRB 260525A: Global MASTER-Net observations report
  71. GRB 260525A: Fermi GBM Final Real-time Localization
  72. GRB 260523B: AstroSat CZTI detection
  73. GRB 260523B: GECAM-B observation
  74. Fermi GRB 260523A: Global MASTER-Net observations report
  75. GRB 260523B: Fermi GBM Final Real-time Localization
  76. GRB 260523A: Fermi GBM Final Real-time Localization
  77. GRB 260522A: Fermi GBM Observation
  78. GRB 260522B: NuSTAR detection of prompt emission
  79. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  80. GRB 260522B: Fermi GBM Final Real-time Localization
  81. GRB 260522A: GOTO optical upper limit
  82. Fermi trigger No 801135305: Global MASTER-Net observations report
  83. Fermi GRB 260522A: Global MASTER-Net observations report
  84. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  85. GRB 260522A: Fermi-LAT detection
  86. GRB 260519C: SVOM/GRM observation
  87. GRB 260522A: Fermi GBM Final Real-time Localization
  88. GRB 260511A: iTelescope T-75 optical detection
  89. GRB 260520B: SVOM/GRM observation
  90. GRB 260411B: TERI Gamma-ray detection
  91. GRB 260407A: TERI Gamma-ray detection
  92. GRB 260307A: TERI Gamma-ray detection
  93. GRB 260225D: TERI Gamma-ray detection
  94. GRB 251118A: TERI Gamma-ray detection
  95. GRB 251113A: TERI Gamma-ray detection
  96. GRB 260428A: TERI Gamma-ray detection
  97. Konus-Wind detection of GRB 260519C
  98. GRB 260520B: Fermi GBM Final Localization
  99. GRB 260509A: SVOM/ECLAIRs refined analysis
  100. GRB 260520A: Fermi GBM Final Localization

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