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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"

28044 results found.

  1. GRB 260226A: Fermi GBM observation
  2. LAT GRB260226.44: Global MASTER-Net observations report
  3. Fermi GRB 260226A: Global MASTER-Net observations report
  4. GRB 260226A: AstroSat CZTI detection of bright long burst
  5. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  6. EP260224a: LCO optical upper limits
  7. GRB 260225A: EP-FXT follow-up observation
  8. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  9. GRB 260223A: Fermi GBM Observation
  10. GRB 260225A: SVOM/VT optical upper limits
  11. EP260223a: Liverpool Telescope upper limits
  12. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  13. EP260224a: Einstein Probe detection of an X-ray transient
  14. EP 260225.148: COLIBRÍ Confirmation of flaring star
  15. EP260223a: Xinglong optical upper limit
  16. GRB 260223A: Glowbug gamma-ray detection
  17. EP260213a: Mephisto optical upper limits
  18. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  19. sb26021801: SVOM/C-GFT upper limit
  20. EP260223a: COLIBRÍ optical upper limits
  21. EP260223a: Einstein Probe detection of an X-ray transient
  22. GRB 260223A: SVOM/GRM observation
  23. GRB 260223A: COLIBRÍ further optical observations and a brightening
  24. EP260221a: Optical upper limit with Kinder observations
  25. GRB 260223A: COLIBRÍ optical observations
  26. GRB 260223A: DDOTI Optical Candidate
  27. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  28. Fermi GRB 260223A: Global MASTER-Net observations report
  29. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  30. EP260221a: COLIBRÍ optical counterpart candidate
  31. EP260221a: Gemini South z-band upper limit
  32. EP260221a: Global MASTER-Net observations report
  33. EP260221a: EP-FXT follow-up observation
  34. Fermi GRB 260221B: Global MASTER-Net observations report
  35. EP-WXT01709258519: Xinglong optical upper limit
  36. EP260221a: Xinglong optical upper limit
  37. Fermi GRB 260221A: Global MASTER-Net observations report
  38. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  39. EP260221a: GOTO optical upper limit
  40. EP260221a: COLIBRÍ optical upper limit
  41. SVOM alert sb26021801: LCO optical upper limit
  42. EP260221a: Einstein Probe detection of an X-ray transient
  43. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  44. Fermi GRB 260219A: Global MASTER-Net observations report
  45. SVOM alert sb26021801: LAST optical upper limit
  46. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. IceCube Alert 260217A: Global MASTER-Net observations report
  48. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  49. sb26021801: SVOM detection of a long faint X-ray transient
  50. EP-WXT 01709258455: NOT optical upper limits
  51. EP260214b: Mondy optical observations
  52. EP260214b: 1.3m DFOT optical upper limit
  53. EP260210a: Mondy optical upper limits
  54. GRB 260208A: AbAO and Terskol optical upper limits
  55. GRB 260208A: continued Mondy optical observations
  56. IPN triangulation of GRB 260212A
  57. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  58. EP260214b: Liverpool Telescope optical observations
  59. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  60. EP260214b: Optical upper limit with Kinder observations
  61. EP260214a: Optical upper limits with Kinder observations
  62. EP260214b: EP-FXT follow-up observation
  63. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  64. EP260214b: DDOTI Optical Detection
  65. EP260214b: GROWTH-India Telescope optical upper limit
  66. EP260214a: VLT near-infrared observation
  67. EP260214a: NOT optical upper limits
  68. EP260214a: COLIBRÍ optical upper limits
  69. EP260214b: OHP/T120 optical observations
  70. EP260214a: refined analysis of the EP-FXT observation
  71. EP260214b: LCO optical counterpart detection
  72. GRB 260211A: SVOM/VT optical counterpart
  73. EP260214b: COLIBRÍ optical observations
  74. EP260214b: NOT optical counterpart detection
  75. EP260214b: Einstein Probe detection of a fast X-ray transient
  76. EP260214a: Global MASTER-Net observations report
  77. EP260214a: Einstein Probe detection of an X-ray transient
  78. GRB 260212A: AstroSat CZTI detection
  79. GRB 260212A: Fermi GBM Observation
  80. EP260213a: Liverpool Telescope optical upper limits
  81. EP260213a: Global MASTER-Net observations report
  82. EP260213a: COLIBRÍ optical upper limits
  83. EP260213a: Optical upper limits with Kinder observations
  84. EP260213a: Mondy R-band optical upper limit
  85. EP260213a: SVOM/C-GFT upper limit
  86. EP260213a: refined analysis of the EP-FXT observation
  87. EP260213a: Einstein Probe detection of a fast X-ray transient
  88. EP/WXT 01709258378: NOT optical upper limits
  89. GRB 260212A: SVOM/GRM observation of a long burst
  90. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  91. GRB 260211A: EP-FXT follow-up observation
  92. GRB 260211A: SVOM/VT optical observation
  93. GRB 260212A: Glowbug gamma-ray detection
  94. Fermi GRB 260212A: Global MASTER-Net observations report
  95. GRB 260211A: LAST optical upper limit
  96. GRB 260210A: SVOM/GRM observation
  97. Fermi GBM Sub-Threshold Detection of GRB 260211A
  98. GRID detection of GRB 260207B
  99. GRB 260211A: LCO optical upper limits
  100. GRB260131A/B: 3.6m DOT Optical Observations

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