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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"

28052 results found.

  1. GRB 260226A: LCOGT Optical Upper Limit
  2. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  3. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  4. GRB 260226A: Glowbug gamma-ray detection
  5. GRB 260226A: NuSTAR detection of bright prompt emission
  6. GRB 260226A : GROWTH-India Telescope optical observations
  7. GRB 260226A: LAST optical upper limit
  8. GRB 260226A: Fermi GBM observation
  9. LAT GRB260226.44: Global MASTER-Net observations report
  10. Fermi GRB 260226A: Global MASTER-Net observations report
  11. GRB 260226A: AstroSat CZTI detection of bright long burst
  12. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  13. EP260224a: LCO optical upper limits
  14. GRB 260225A: EP-FXT follow-up observation
  15. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  16. GRB 260223A: Fermi GBM Observation
  17. GRB 260225A: SVOM/VT optical upper limits
  18. EP260223a: Liverpool Telescope upper limits
  19. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  20. EP260224a: Einstein Probe detection of an X-ray transient
  21. EP 260225.148: COLIBRÍ Confirmation of flaring star
  22. EP260223a: Xinglong optical upper limit
  23. GRB 260223A: Glowbug gamma-ray detection
  24. EP260213a: Mephisto optical upper limits
  25. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  26. sb26021801: SVOM/C-GFT upper limit
  27. EP260223a: COLIBRÍ optical upper limits
  28. EP260223a: Einstein Probe detection of an X-ray transient
  29. GRB 260223A: SVOM/GRM observation
  30. GRB 260223A: COLIBRÍ further optical observations and a brightening
  31. EP260221a: Optical upper limit with Kinder observations
  32. GRB 260223A: COLIBRÍ optical observations
  33. GRB 260223A: DDOTI Optical Candidate
  34. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  35. Fermi GRB 260223A: Global MASTER-Net observations report
  36. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  37. EP260221a: COLIBRÍ optical counterpart candidate
  38. EP260221a: Gemini South z-band upper limit
  39. EP260221a: Global MASTER-Net observations report
  40. EP260221a: EP-FXT follow-up observation
  41. Fermi GRB 260221B: Global MASTER-Net observations report
  42. EP-WXT01709258519: Xinglong optical upper limit
  43. EP260221a: Xinglong optical upper limit
  44. Fermi GRB 260221A: Global MASTER-Net observations report
  45. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  46. EP260221a: GOTO optical upper limit
  47. EP260221a: COLIBRÍ optical upper limit
  48. SVOM alert sb26021801: LCO optical upper limit
  49. EP260221a: Einstein Probe detection of an X-ray transient
  50. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  51. Fermi GRB 260219A: Global MASTER-Net observations report
  52. SVOM alert sb26021801: LAST optical upper limit
  53. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. IceCube Alert 260217A: Global MASTER-Net observations report
  55. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  56. sb26021801: SVOM detection of a long faint X-ray transient
  57. EP-WXT 01709258455: NOT optical upper limits
  58. EP260214b: Mondy optical observations
  59. EP260214b: 1.3m DFOT optical upper limit
  60. EP260210a: Mondy optical upper limits
  61. GRB 260208A: AbAO and Terskol optical upper limits
  62. GRB 260208A: continued Mondy optical observations
  63. IPN triangulation of GRB 260212A
  64. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  65. EP260214b: Liverpool Telescope optical observations
  66. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  67. EP260214b: Optical upper limit with Kinder observations
  68. EP260214a: Optical upper limits with Kinder observations
  69. EP260214b: EP-FXT follow-up observation
  70. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  71. EP260214b: DDOTI Optical Detection
  72. EP260214b: GROWTH-India Telescope optical upper limit
  73. EP260214a: VLT near-infrared observation
  74. EP260214a: NOT optical upper limits
  75. EP260214a: COLIBRÍ optical upper limits
  76. EP260214b: OHP/T120 optical observations
  77. EP260214a: refined analysis of the EP-FXT observation
  78. EP260214b: LCO optical counterpart detection
  79. GRB 260211A: SVOM/VT optical counterpart
  80. EP260214b: COLIBRÍ optical observations
  81. EP260214b: NOT optical counterpart detection
  82. EP260214b: Einstein Probe detection of a fast X-ray transient
  83. EP260214a: Global MASTER-Net observations report
  84. EP260214a: Einstein Probe detection of an X-ray transient
  85. GRB 260212A: AstroSat CZTI detection
  86. GRB 260212A: Fermi GBM Observation
  87. EP260213a: Liverpool Telescope optical upper limits
  88. EP260213a: Global MASTER-Net observations report
  89. EP260213a: COLIBRÍ optical upper limits
  90. EP260213a: Optical upper limits with Kinder observations
  91. EP260213a: Mondy R-band optical upper limit
  92. EP260213a: SVOM/C-GFT upper limit
  93. EP260213a: refined analysis of the EP-FXT observation
  94. EP260213a: Einstein Probe detection of a fast X-ray transient
  95. EP/WXT 01709258378: NOT optical upper limits
  96. GRB 260212A: SVOM/GRM observation of a long burst
  97. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  98. GRB 260211A: EP-FXT follow-up observation
  99. GRB 260211A: SVOM/VT optical observation
  100. GRB 260212A: Glowbug gamma-ray detection

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