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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"

28059 results found.

  1. GRB 260604C: Jinshan optical observations
  2. GRB 260604C: Fermi GBM Observation
  3. EP260602d: J-band upper limit with WINTER
  4. EP260602b: J-band upper limit with WINTER
  5. GRB 260604C: LAST detection of optical counterpart candidate
  6. Fermi GRB 260604C: Global MASTER-Net observations report
  7. Fermi GRB 260604C: Global MASTER-Net observations report
  8. SVOM GRB260604.85: Global MASTER-Net observations report
  9. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  10. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  11. EP260602a: EP-FXT follow-up observation
  12. EP260603a: Global MASTER-Net observations report
  13. EP260603a: Einstein Probe detection of a fast X-ray transient
  14. EP260602d: Optical Upper limits with kinder observations
  15. EP260602b: Liverpool Telescope observations
  16. EP260602a: Liverpool Telescope optical upper limits
  17. EP260602b: Liverpool Telescope and LCO observations
  18. EP260602a: GTC and Liverpool Telescope optical observations
  19. EP260601a/GRB 260601B: EP-FXT follow-up observation
  20. GRB 260601B / EP260601a: Mondy optical upper limit
  21. EP260602b: EP-FXT follow-up observation
  22. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  23. GRB 260603A: Kilonova-Catcher optical upper limit
  24. GRB 260603A: SVOM/VT optical observations
  25. EP260602a: NOT NIR J-band observations
  26. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  27. EP260602d: Einstein Probe detection of a fast X-ray transient
  28. Fermi trigger No 802141998: Global MASTER-Net observations report
  29. GRB 260601A: SVOM/GRM observation of a short burst
  30. EP260602c: Einstein Probe detection of a fast X-ray transient
  31. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  32. EP260602a: COLIBRÍ optical observations
  33. GRB260601B/EP260601a: NOT near-infrared observations
  34. SVOM GRB260603.23: Global MASTER-Net observations report
  35. GRB 260603A: SVOM detection of a burst
  36. EP260602b: Einstein Probe detection of a fast X-ray transient
  37. Fermi GRB 260602B: Global MASTER-Net observations report
  38. Fermi GRB 260602B: Global MASTER-Net observations report
  39. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  40. EP260602a: SVOM/VT optical candidate
  41. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  42. GRB 260601B/EP260601a: J-band upper limit with WINTER
  43. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  44. EP260530a/AT 2026nwl: KAIT optical observations
  45. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  46. EP260602a: Optical upper limits with Kinder observations
  47. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  48. EP260602a: Einstein Probe detection of a fast X-ray transient
  49. GRB 260601B/EP260601a: SVOM/VT optical observations
  50. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  51. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  52. EP260601a: Einstein Probe detection of an X-ray transient
  53. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  54. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  55. GRB 260601A: Glowbug gamma-ray detection of a short burst
  56. GRB 260531B: Glowbug gamma-ray detection
  57. GRB 260601A: Fermi GBM Observation
  58. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  59. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  60. Fermi GRB 260601A: Global MASTER-Net observations report
  61. GRB 260601A: Fermi GBM Final Real-time Localization
  62. The EP-WXT trigger 01709266272 is likely a flaring star
  63. AT2026nik: EP-FXT X-ray counterpart
  64. Fermi trigger No 801900520: Global MASTER-Net observations report
  65. GRB 260531A: MAXI/GSC detection
  66. AT 2026nuz: COLIBRÍ optical observations
  67. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  68. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  69. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  70. Fermi GRB 260529A: Global MASTER-Net observations report
  71. EP260526a: SVOM/VT optical upper limits
  72. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  73. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  74. EP260527a/GRB 260527A: EP-FXT follow-up observation
  75. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  76. EP260527a: SVOM/VT optical observation
  77. EP260527a: COLIBRÍ optical detection
  78. EP260527a: Einstein Probe detection of a fast X-ray transient
  79. Fermi trigger No 801580882: Global MASTER-Net observations report
  80. EP260526a: LCO optical upper limits
  81. EP260526a: Einstein Probe detection of a fast X-ray transient
  82. EP260526.405: COLIBRÍ optical upper limits
  83. The EP-WXT trigger 01709266106 is not a real source
  84. Fermi GRB 260526A: Global MASTER-Net observations report
  85. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  86. EP-WXT 01709266106: NOT optical upper limits
  87. Fermi GRB 260525A: Global MASTER-Net observations report
  88. GRB 260523B: AstroSat CZTI detection
  89. Fermi GRB 260523A: Global MASTER-Net observations report
  90. GRB 260522A: Fermi GBM Observation
  91. GRB 260522B: NuSTAR detection of prompt emission
  92. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  93. Fermi trigger No 801135305: Global MASTER-Net observations report
  94. Fermi GRB 260522A: Global MASTER-Net observations report
  95. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  96. GRB 260511A: iTelescope T-75 optical detection
  97. GRB 260520B: SVOM/GRM observation
  98. GRB 260411B: TERI Gamma-ray detection
  99. GRB 260407A: TERI Gamma-ray detection
  100. GRB 260307A: TERI Gamma-ray detection

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