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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"

28051 results found.

  1. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  2. EP260602a: EP-FXT follow-up observation
  3. EP260603a: Global MASTER-Net observations report
  4. EP260603a: Einstein Probe detection of a fast X-ray transient
  5. EP260602d: Optical Upper limits with kinder observations
  6. EP260602b: Liverpool Telescope observations
  7. EP260602a: Liverpool Telescope optical upper limits
  8. EP260602b: Liverpool Telescope and LCO observations
  9. EP260602a: GTC and Liverpool Telescope optical observations
  10. EP260601a/GRB 260601B: EP-FXT follow-up observation
  11. GRB 260601B / EP260601a: Mondy optical upper limit
  12. EP260602b: EP-FXT follow-up observation
  13. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  14. GRB 260603A: Kilonova-Catcher optical upper limit
  15. GRB 260603A: SVOM/VT optical observations
  16. EP260602a: NOT NIR J-band observations
  17. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  18. EP260602d: Einstein Probe detection of a fast X-ray transient
  19. Fermi trigger No 802141998: Global MASTER-Net observations report
  20. GRB 260601A: SVOM/GRM observation of a short burst
  21. EP260602c: Einstein Probe detection of a fast X-ray transient
  22. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  23. EP260602a: COLIBRÍ optical observations
  24. GRB260601B/EP260601a: NOT near-infrared observations
  25. SVOM GRB260603.23: Global MASTER-Net observations report
  26. GRB 260603A: SVOM detection of a burst
  27. EP260602b: Einstein Probe detection of a fast X-ray transient
  28. Fermi GRB 260602B: Global MASTER-Net observations report
  29. Fermi GRB 260602B: Global MASTER-Net observations report
  30. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  31. EP260602a: SVOM/VT optical candidate
  32. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  33. GRB 260601B/EP260601a: J-band upper limit with WINTER
  34. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  35. EP260530a/AT 2026nwl: KAIT optical observations
  36. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  37. EP260602a: Optical upper limits with Kinder observations
  38. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  39. EP260602a: Einstein Probe detection of a fast X-ray transient
  40. GRB 260601B/EP260601a: SVOM/VT optical observations
  41. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  42. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  43. EP260601a: Einstein Probe detection of an X-ray transient
  44. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  45. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  46. GRB 260601A: Glowbug gamma-ray detection of a short burst
  47. GRB 260531B: Glowbug gamma-ray detection
  48. GRB 260601A: Fermi GBM Observation
  49. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  50. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  51. Fermi GRB 260601A: Global MASTER-Net observations report
  52. GRB 260601A: Fermi GBM Final Real-time Localization
  53. The EP-WXT trigger 01709266272 is likely a flaring star
  54. AT2026nik: EP-FXT X-ray counterpart
  55. Fermi trigger No 801900520: Global MASTER-Net observations report
  56. GRB 260531A: MAXI/GSC detection
  57. AT 2026nuz: COLIBRÍ optical observations
  58. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  59. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  60. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  61. Fermi GRB 260529A: Global MASTER-Net observations report
  62. EP260526a: SVOM/VT optical upper limits
  63. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  64. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  65. EP260527a/GRB 260527A: EP-FXT follow-up observation
  66. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  67. EP260527a: SVOM/VT optical observation
  68. EP260527a: COLIBRÍ optical detection
  69. EP260527a: Einstein Probe detection of a fast X-ray transient
  70. Fermi trigger No 801580882: Global MASTER-Net observations report
  71. EP260526a: LCO optical upper limits
  72. EP260526a: Einstein Probe detection of a fast X-ray transient
  73. EP260526.405: COLIBRÍ optical upper limits
  74. The EP-WXT trigger 01709266106 is not a real source
  75. Fermi GRB 260526A: Global MASTER-Net observations report
  76. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  77. EP-WXT 01709266106: NOT optical upper limits
  78. Fermi GRB 260525A: Global MASTER-Net observations report
  79. GRB 260523B: AstroSat CZTI detection
  80. Fermi GRB 260523A: Global MASTER-Net observations report
  81. GRB 260522A: Fermi GBM Observation
  82. GRB 260522B: NuSTAR detection of prompt emission
  83. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  84. Fermi trigger No 801135305: Global MASTER-Net observations report
  85. Fermi GRB 260522A: Global MASTER-Net observations report
  86. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  87. GRB 260511A: iTelescope T-75 optical detection
  88. GRB 260520B: SVOM/GRM observation
  89. GRB 260411B: TERI Gamma-ray detection
  90. GRB 260407A: TERI Gamma-ray detection
  91. GRB 260307A: TERI Gamma-ray detection
  92. GRB 260225D: TERI Gamma-ray detection
  93. GRB 251118A: TERI Gamma-ray detection
  94. GRB 251113A: TERI Gamma-ray detection
  95. GRB 260428A: TERI Gamma-ray detection
  96. GRB 260519C: NuSTAR detection of prompt emission
  97. Konus-Wind detection of GRB 260518A
  98. GRB 260516D: SVOM/ECLAIRs refined analysis
  99. GRB 260421B: radio detection with the VLA
  100. GRB 260509A: CrAO ZTSh optical upper limit

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