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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"

28038 results found.

  1. EP260602b: EP-FXT follow-up observation
  2. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  3. GRB 260603A: Kilonova-Catcher optical upper limit
  4. GRB 260603A: SVOM/VT optical observations
  5. EP260602a: NOT NIR J-band observations
  6. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  7. EP260602d: Einstein Probe detection of a fast X-ray transient
  8. Fermi trigger No 802141998: Global MASTER-Net observations report
  9. GRB 260601A: SVOM/GRM observation of a short burst
  10. EP260602c: Einstein Probe detection of a fast X-ray transient
  11. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  12. EP260602a: COLIBRÍ optical observations
  13. GRB260601B/EP260601a: NOT near-infrared observations
  14. SVOM GRB260603.23: Global MASTER-Net observations report
  15. GRB 260603A: SVOM detection of a burst
  16. EP260602b: Einstein Probe detection of a fast X-ray transient
  17. Fermi GRB 260602B: Global MASTER-Net observations report
  18. Fermi GRB 260602B: Global MASTER-Net observations report
  19. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  20. EP260602a: SVOM/VT optical candidate
  21. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  22. GRB 260601B/EP260601a: J-band upper limit with WINTER
  23. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  24. EP260530a/AT 2026nwl: KAIT optical observations
  25. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  26. EP260602a: Optical upper limits with Kinder observations
  27. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  28. EP260602a: Einstein Probe detection of a fast X-ray transient
  29. GRB 260601B/EP260601a: SVOM/VT optical observations
  30. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  31. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  32. EP260601a: Einstein Probe detection of an X-ray transient
  33. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  34. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  35. GRB 260601A: Glowbug gamma-ray detection of a short burst
  36. GRB 260531B: Glowbug gamma-ray detection
  37. GRB 260601A: Fermi GBM Observation
  38. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  39. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  40. Fermi GRB 260601A: Global MASTER-Net observations report
  41. GRB 260601A: Fermi GBM Final Real-time Localization
  42. The EP-WXT trigger 01709266272 is likely a flaring star
  43. AT2026nik: EP-FXT X-ray counterpart
  44. Fermi trigger No 801900520: Global MASTER-Net observations report
  45. GRB 260531A: MAXI/GSC detection
  46. AT 2026nuz: COLIBRÍ optical observations
  47. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  48. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  49. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  50. Fermi GRB 260529A: Global MASTER-Net observations report
  51. EP260526a: SVOM/VT optical upper limits
  52. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  53. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  54. EP260527a/GRB 260527A: EP-FXT follow-up observation
  55. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  56. EP260527a: SVOM/VT optical observation
  57. EP260527a: COLIBRÍ optical detection
  58. EP260527a: Einstein Probe detection of a fast X-ray transient
  59. Fermi trigger No 801580882: Global MASTER-Net observations report
  60. EP260526a: LCO optical upper limits
  61. EP260526a: Einstein Probe detection of a fast X-ray transient
  62. EP260526.405: COLIBRÍ optical upper limits
  63. The EP-WXT trigger 01709266106 is not a real source
  64. Fermi GRB 260526A: Global MASTER-Net observations report
  65. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  66. EP-WXT 01709266106: NOT optical upper limits
  67. Fermi GRB 260525A: Global MASTER-Net observations report
  68. GRB 260523B: AstroSat CZTI detection
  69. Fermi GRB 260523A: Global MASTER-Net observations report
  70. GRB 260522A: Fermi GBM Observation
  71. GRB 260522B: NuSTAR detection of prompt emission
  72. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  73. Fermi trigger No 801135305: Global MASTER-Net observations report
  74. Fermi GRB 260522A: Global MASTER-Net observations report
  75. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  76. GRB 260511A: iTelescope T-75 optical detection
  77. GRB 260520B: SVOM/GRM observation
  78. GRB 260411B: TERI Gamma-ray detection
  79. GRB 260407A: TERI Gamma-ray detection
  80. GRB 260307A: TERI Gamma-ray detection
  81. GRB 260225D: TERI Gamma-ray detection
  82. GRB 251118A: TERI Gamma-ray detection
  83. GRB 251113A: TERI Gamma-ray detection
  84. GRB 260428A: TERI Gamma-ray detection
  85. GRB 260519C: NuSTAR detection of prompt emission
  86. Konus-Wind detection of GRB 260518A
  87. GRB 260516D: SVOM/ECLAIRs refined analysis
  88. GRB 260421B: radio detection with the VLA
  89. GRB 260509A: CrAO ZTSh optical upper limit
  90. GRB 260516D: GOTO optical counterpart detection
  91. GRB 260516D: LCO optical observations
  92. GRB 260515A: further Liverpool Telescope observations
  93. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  94. GRB 260516D: GROWTH-India Telescope optical detection
  95. GRB 260516D: SVOM/VT optical bright candidate
  96. GRB 260515A: CrAO ZTSh BVRI optical observations
  97. Fermi GRB 260516C: Global MASTER-Net observations report
  98. SVOM GRB260516D: Global MASTER-Net observations report
  99. GRB 260516D: SVOM possible detection of a burst
  100. GRB 260515A: LCO optical counterpart detection

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