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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"

18335 results found.

  1. EP260213a: Mephisto optical upper limits
  2. EP260223a: EP-FXT follow-up observation
  3. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  4. sb26021801: SVOM/C-GFT upper limit
  5. EP260223a: COLIBRÍ optical upper limits
  6. EP260223a: Einstein Probe detection of an X-ray transient
  7. GRB 260223A: SVOM/GRM observation
  8. GRB 260223A: COLIBRÍ further optical observations and a brightening
  9. EP260221a: Optical upper limit with Kinder observations
  10. GRB 260223A: COLIBRÍ optical observations
  11. GRB 260223A: DDOTI Optical Candidate
  12. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  13. EP260221a: COLIBRÍ optical counterpart candidate
  14. EP260221a: Gemini South z-band upper limit
  15. EP260221a: EP-FXT follow-up observation
  16. EP-WXT01709258519: Xinglong optical upper limit
  17. EP260221a: Xinglong optical upper limit
  18. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  19. EP260221a: GOTO optical upper limit
  20. EP260221a: COLIBRÍ optical upper limit
  21. SVOM alert sb26021801: LCO optical upper limit
  22. EP260221a: Einstein Probe detection of an X-ray transient
  23. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  24. SVOM alert sb26021801: LAST optical upper limit
  25. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  26. The EP-WXT trigger 01709258455 is likely a flaring star
  27. EP-WXT 01709258455: NOT optical upper limits
  28. EP260214b: Mondy optical observations
  29. EP260214b: 1.3m DFOT optical upper limit
  30. EP260210a: Mondy optical upper limits
  31. Konus-Wind detection of GRB 260212A
  32. GRB 260208A: AbAO and Terskol optical upper limits
  33. GRB 260208A: continued Mondy optical observations
  34. IPN triangulation of GRB 260212A
  35. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  36. EP260214b: Liverpool Telescope optical observations
  37. EP260214b: Optical upper limit with Kinder observations
  38. EP260214a: Optical upper limits with Kinder observations
  39. EP260214b: EP-FXT follow-up observation
  40. EP260214b: DDOTI Optical Detection
  41. EP260214b: GROWTH-India Telescope optical upper limit
  42. EP260214a: VLT near-infrared observation
  43. EP260214a: NOT optical upper limits
  44. EP260214a: COLIBRÍ optical upper limits
  45. EP260214b: OHP/T120 optical observations
  46. EP260214a: refined analysis of the EP-FXT observation
  47. EP260214b: LCO optical counterpart detection
  48. EP260214b: COLIBRÍ optical observations
  49. EP260214b: NOT optical counterpart detection
  50. EP260214b: Einstein Probe detection of a fast X-ray transient
  51. EP260214a: Einstein Probe detection of an X-ray transient
  52. EP260213a: Liverpool Telescope optical upper limits
  53. EP260213a: COLIBRÍ optical upper limits
  54. EP260213a: Optical upper limits with Kinder observations
  55. EP260213a: Mondy R-band optical upper limit
  56. EP260213a: SVOM/C-GFT upper limit
  57. EP260213a: refined analysis of the EP-FXT observation
  58. EP260213a: Einstein Probe detection of a fast X-ray transient
  59. EP/WXT 01709258378: NOT optical upper limits
  60. GRB 260212A: SVOM/GRM observation of a long burst
  61. GRB 260211A: EP-FXT follow-up observation
  62. GRB 260211A: LAST optical upper limit
  63. GRB 260210A: SVOM/GRM observation
  64. Konus-Wind detection of GRB 260207B
  65. GRB 260211A: LCO optical upper limits
  66. GRB260131A/B: 3.6m DOT Optical Observations
  67. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  68. EP260209a: COLIBRÍ optical upper limit
  69. EP260209a: LCO optical upper limits
  70. EP260210a: refined analysis of the EP-FXT observation
  71. GRB 260208A: LCO detection of the optical counterpart
  72. EP260209a: Einstein Probe detection of a fast X-ray transient
  73. EP260210a: Optical upper limits with Kinder observations
  74. GRB 260210A: AstroSat CZTI detection
  75. EP260210a: COLIBRÍ optical upper limit
  76. EP260210a: SVOM/C-GFT upper limit
  77. GRB 260208B: refined analysis of the EP-FXT observation
  78. EP260210a: Einstein Probe detection of an X-ray transient
  79. GRB 260208C: SVOM/GRM observation
  80. GRB 260204A: Swift-XRT afterglow detection
  81. GRB260208A: Liverpool Telescope optical follow-up observations
  82. GRB 260131A/B: continued Mondy optical observations
  83. GRB 260204A: Swift/UVOT Upper Limits
  84. GRB 260208B: COLIBRÍ optical observations
  85. GRB 260208A: Mondy optical observations
  86. GRB 260208A: 1.3m DFOT optical detection
  87. GRB 260208A: COLIBRÍ optical observations
  88. GRB 260208B: EP-FXT observation
  89. GRB 260208A: NOT spectroscopic redshift z = 2.36
  90. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  91. GRB 260209A: Fermi GBM Final Real-time Localization
  92. GRB 260208A: SVOM/VT optical observation
  93. GRB 260208B: SVOM/GRM observation of a bright burst
  94. LAT GRB 260208B: Global MASTER-Net observations report
  95. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  96. GRB 260131A/B: Mondy and Terskol optical observations
  97. GRB 260204A: SVOM/VT optical candidate
  98. GRB 260204A: LCO optical upper limits
  99. EP260110a: Late GTC/EMIR near-infrared observations
  100. GRB 260131A: KAIT optical observations

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