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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"

28054 results found.

  1. EP260602b: J-band upper limit with WINTER
  2. GRB 260604C: LAST detection of optical counterpart candidate
  3. Fermi GRB 260604C: Global MASTER-Net observations report
  4. Fermi GRB 260604C: Global MASTER-Net observations report
  5. SVOM GRB260604.85: Global MASTER-Net observations report
  6. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  7. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  8. EP260602a: EP-FXT follow-up observation
  9. EP260603a: Global MASTER-Net observations report
  10. EP260603a: Einstein Probe detection of a fast X-ray transient
  11. EP260602d: Optical Upper limits with kinder observations
  12. EP260602b: Liverpool Telescope observations
  13. EP260602a: Liverpool Telescope optical upper limits
  14. EP260602b: Liverpool Telescope and LCO observations
  15. EP260602a: GTC and Liverpool Telescope optical observations
  16. EP260601a/GRB 260601B: EP-FXT follow-up observation
  17. GRB 260601B / EP260601a: Mondy optical upper limit
  18. EP260602b: EP-FXT follow-up observation
  19. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  20. GRB 260603A: Kilonova-Catcher optical upper limit
  21. GRB 260603A: SVOM/VT optical observations
  22. EP260602a: NOT NIR J-band observations
  23. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  24. EP260602d: Einstein Probe detection of a fast X-ray transient
  25. Fermi trigger No 802141998: Global MASTER-Net observations report
  26. GRB 260601A: SVOM/GRM observation of a short burst
  27. EP260602c: Einstein Probe detection of a fast X-ray transient
  28. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  29. EP260602a: COLIBRÍ optical observations
  30. GRB260601B/EP260601a: NOT near-infrared observations
  31. SVOM GRB260603.23: Global MASTER-Net observations report
  32. GRB 260603A: SVOM detection of a burst
  33. EP260602b: Einstein Probe detection of a fast X-ray transient
  34. Fermi GRB 260602B: Global MASTER-Net observations report
  35. Fermi GRB 260602B: Global MASTER-Net observations report
  36. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  37. EP260602a: SVOM/VT optical candidate
  38. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  39. GRB 260601B/EP260601a: J-band upper limit with WINTER
  40. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  41. EP260530a/AT 2026nwl: KAIT optical observations
  42. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  43. EP260602a: Optical upper limits with Kinder observations
  44. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  45. EP260602a: Einstein Probe detection of a fast X-ray transient
  46. GRB 260601B/EP260601a: SVOM/VT optical observations
  47. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  48. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  49. EP260601a: Einstein Probe detection of an X-ray transient
  50. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  51. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  52. GRB 260601A: Glowbug gamma-ray detection of a short burst
  53. GRB 260531B: Glowbug gamma-ray detection
  54. GRB 260601A: Fermi GBM Observation
  55. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  56. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  57. Fermi GRB 260601A: Global MASTER-Net observations report
  58. GRB 260601A: Fermi GBM Final Real-time Localization
  59. The EP-WXT trigger 01709266272 is likely a flaring star
  60. AT2026nik: EP-FXT X-ray counterpart
  61. Fermi trigger No 801900520: Global MASTER-Net observations report
  62. GRB 260531A: MAXI/GSC detection
  63. AT 2026nuz: COLIBRÍ optical observations
  64. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  65. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  66. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  67. Fermi GRB 260529A: Global MASTER-Net observations report
  68. EP260526a: SVOM/VT optical upper limits
  69. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  70. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  71. EP260527a/GRB 260527A: EP-FXT follow-up observation
  72. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  73. EP260527a: SVOM/VT optical observation
  74. EP260527a: COLIBRÍ optical detection
  75. EP260527a: Einstein Probe detection of a fast X-ray transient
  76. Fermi trigger No 801580882: Global MASTER-Net observations report
  77. EP260526a: LCO optical upper limits
  78. EP260526a: Einstein Probe detection of a fast X-ray transient
  79. EP260526.405: COLIBRÍ optical upper limits
  80. The EP-WXT trigger 01709266106 is not a real source
  81. Fermi GRB 260526A: Global MASTER-Net observations report
  82. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  83. EP-WXT 01709266106: NOT optical upper limits
  84. Fermi GRB 260525A: Global MASTER-Net observations report
  85. GRB 260523B: AstroSat CZTI detection
  86. Fermi GRB 260523A: Global MASTER-Net observations report
  87. GRB 260522A: Fermi GBM Observation
  88. GRB 260522B: NuSTAR detection of prompt emission
  89. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  90. Fermi trigger No 801135305: Global MASTER-Net observations report
  91. Fermi GRB 260522A: Global MASTER-Net observations report
  92. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  93. GRB 260511A: iTelescope T-75 optical detection
  94. GRB 260520B: SVOM/GRM observation
  95. GRB 260411B: TERI Gamma-ray detection
  96. GRB 260407A: TERI Gamma-ray detection
  97. GRB 260307A: TERI Gamma-ray detection
  98. GRB 260225D: TERI Gamma-ray detection
  99. GRB 251118A: TERI Gamma-ray detection
  100. GRB 251113A: TERI Gamma-ray detection

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