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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"

28037 results found.

  1. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  2. GRB 260223A: Fermi GBM Observation
  3. GRB 260225A: SVOM/VT optical upper limits
  4. EP260223a: Liverpool Telescope upper limits
  5. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  6. EP260224a: Einstein Probe detection of an X-ray transient
  7. EP 260225.148: COLIBRÍ Confirmation of flaring star
  8. EP260223a: Xinglong optical upper limit
  9. GRB 260223A: Glowbug gamma-ray detection
  10. EP260213a: Mephisto optical upper limits
  11. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  12. sb26021801: SVOM/C-GFT upper limit
  13. EP260223a: COLIBRÍ optical upper limits
  14. EP260223a: Einstein Probe detection of an X-ray transient
  15. GRB 260223A: SVOM/GRM observation
  16. GRB 260223A: COLIBRÍ further optical observations and a brightening
  17. EP260221a: Optical upper limit with Kinder observations
  18. GRB 260223A: COLIBRÍ optical observations
  19. GRB 260223A: DDOTI Optical Candidate
  20. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  21. Fermi GRB 260223A: Global MASTER-Net observations report
  22. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  23. EP260221a: COLIBRÍ optical counterpart candidate
  24. EP260221a: Gemini South z-band upper limit
  25. EP260221a: Global MASTER-Net observations report
  26. EP260221a: EP-FXT follow-up observation
  27. Fermi GRB 260221B: Global MASTER-Net observations report
  28. EP-WXT01709258519: Xinglong optical upper limit
  29. EP260221a: Xinglong optical upper limit
  30. Fermi GRB 260221A: Global MASTER-Net observations report
  31. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  32. EP260221a: GOTO optical upper limit
  33. EP260221a: COLIBRÍ optical upper limit
  34. SVOM alert sb26021801: LCO optical upper limit
  35. EP260221a: Einstein Probe detection of an X-ray transient
  36. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  37. Fermi GRB 260219A: Global MASTER-Net observations report
  38. SVOM alert sb26021801: LAST optical upper limit
  39. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. IceCube Alert 260217A: Global MASTER-Net observations report
  41. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  42. sb26021801: SVOM detection of a long faint X-ray transient
  43. EP-WXT 01709258455: NOT optical upper limits
  44. EP260214b: Mondy optical observations
  45. EP260214b: 1.3m DFOT optical upper limit
  46. EP260210a: Mondy optical upper limits
  47. GRB 260208A: AbAO and Terskol optical upper limits
  48. GRB 260208A: continued Mondy optical observations
  49. IPN triangulation of GRB 260212A
  50. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  51. EP260214b: Liverpool Telescope optical observations
  52. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  53. EP260214b: Optical upper limit with Kinder observations
  54. EP260214a: Optical upper limits with Kinder observations
  55. EP260214b: EP-FXT follow-up observation
  56. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  57. EP260214b: DDOTI Optical Detection
  58. EP260214b: GROWTH-India Telescope optical upper limit
  59. EP260214a: VLT near-infrared observation
  60. EP260214a: NOT optical upper limits
  61. EP260214a: COLIBRÍ optical upper limits
  62. EP260214b: OHP/T120 optical observations
  63. EP260214a: refined analysis of the EP-FXT observation
  64. EP260214b: LCO optical counterpart detection
  65. GRB 260211A: SVOM/VT optical counterpart
  66. EP260214b: COLIBRÍ optical observations
  67. EP260214b: NOT optical counterpart detection
  68. EP260214b: Einstein Probe detection of a fast X-ray transient
  69. EP260214a: Global MASTER-Net observations report
  70. EP260214a: Einstein Probe detection of an X-ray transient
  71. GRB 260212A: AstroSat CZTI detection
  72. GRB 260212A: Fermi GBM Observation
  73. EP260213a: Liverpool Telescope optical upper limits
  74. EP260213a: Global MASTER-Net observations report
  75. EP260213a: COLIBRÍ optical upper limits
  76. EP260213a: Optical upper limits with Kinder observations
  77. EP260213a: Mondy R-band optical upper limit
  78. EP260213a: SVOM/C-GFT upper limit
  79. EP260213a: refined analysis of the EP-FXT observation
  80. EP260213a: Einstein Probe detection of a fast X-ray transient
  81. EP/WXT 01709258378: NOT optical upper limits
  82. GRB 260212A: SVOM/GRM observation of a long burst
  83. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  84. GRB 260211A: EP-FXT follow-up observation
  85. GRB 260211A: SVOM/VT optical observation
  86. GRB 260212A: Glowbug gamma-ray detection
  87. Fermi GRB 260212A: Global MASTER-Net observations report
  88. GRB 260211A: LAST optical upper limit
  89. GRB 260210A: SVOM/GRM observation
  90. Fermi GBM Sub-Threshold Detection of GRB 260211A
  91. GRID detection of GRB 260207B
  92. GRB 260211A: LCO optical upper limits
  93. GRB260131A/B: 3.6m DOT Optical Observations
  94. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  95. Fermi trigger No 792537871: Global MASTER-Net observations report
  96. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  97. EP260209a: COLIBRÍ optical upper limit
  98. Fermi GRB 260210C: Global MASTER-Net observations report
  99. EP260209a: LCO optical upper limits
  100. EP260210a: Global MASTER-Net observations report

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