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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"

28039 results found.

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

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