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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"

28042 results found.

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

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