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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"

27642 results found.

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

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