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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"

28058 results found.

  1. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  2. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  3. EP260214a: VLT/FORS2 optical observations
  4. GRB 260225A: WINTER J-band upper limit
  5. GRB 260226A: COLIBRÍ optical upper limits
  6. GRB 260226A: LCOGT Optical Upper Limit
  7. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  8. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  9. GRB 260226A: Glowbug gamma-ray detection
  10. GRB 260226A: NuSTAR detection of bright prompt emission
  11. GRB 260226A : GROWTH-India Telescope optical observations
  12. GRB 260226A: LAST optical upper limit
  13. GRB 260226A: Fermi GBM observation
  14. LAT GRB260226.44: Global MASTER-Net observations report
  15. Fermi GRB 260226A: Global MASTER-Net observations report
  16. GRB 260226A: AstroSat CZTI detection of bright long burst
  17. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  18. EP260224a: LCO optical upper limits
  19. GRB 260225A: EP-FXT follow-up observation
  20. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  21. GRB 260223A: Fermi GBM Observation
  22. GRB 260225A: SVOM/VT optical upper limits
  23. EP260223a: Liverpool Telescope upper limits
  24. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  25. EP260224a: Einstein Probe detection of an X-ray transient
  26. EP 260225.148: COLIBRÍ Confirmation of flaring star
  27. EP260223a: Xinglong optical upper limit
  28. GRB 260223A: Glowbug gamma-ray detection
  29. EP260213a: Mephisto optical upper limits
  30. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  31. sb26021801: SVOM/C-GFT upper limit
  32. EP260223a: COLIBRÍ optical upper limits
  33. EP260223a: Einstein Probe detection of an X-ray transient
  34. GRB 260223A: SVOM/GRM observation
  35. GRB 260223A: COLIBRÍ further optical observations and a brightening
  36. EP260221a: Optical upper limit with Kinder observations
  37. GRB 260223A: COLIBRÍ optical observations
  38. GRB 260223A: DDOTI Optical Candidate
  39. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  40. Fermi GRB 260223A: Global MASTER-Net observations report
  41. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  42. EP260221a: COLIBRÍ optical counterpart candidate
  43. EP260221a: Gemini South z-band upper limit
  44. EP260221a: Global MASTER-Net observations report
  45. EP260221a: EP-FXT follow-up observation
  46. Fermi GRB 260221B: Global MASTER-Net observations report
  47. EP-WXT01709258519: Xinglong optical upper limit
  48. EP260221a: Xinglong optical upper limit
  49. Fermi GRB 260221A: Global MASTER-Net observations report
  50. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  51. EP260221a: GOTO optical upper limit
  52. EP260221a: COLIBRÍ optical upper limit
  53. SVOM alert sb26021801: LCO optical upper limit
  54. EP260221a: Einstein Probe detection of an X-ray transient
  55. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  56. Fermi GRB 260219A: Global MASTER-Net observations report
  57. SVOM alert sb26021801: LAST optical upper limit
  58. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  59. IceCube Alert 260217A: Global MASTER-Net observations report
  60. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  61. sb26021801: SVOM detection of a long faint X-ray transient
  62. EP-WXT 01709258455: NOT optical upper limits
  63. EP260214b: Mondy optical observations
  64. EP260214b: 1.3m DFOT optical upper limit
  65. EP260210a: Mondy optical upper limits
  66. GRB 260208A: AbAO and Terskol optical upper limits
  67. GRB 260208A: continued Mondy optical observations
  68. IPN triangulation of GRB 260212A
  69. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  70. EP260214b: Liverpool Telescope optical observations
  71. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  72. EP260214b: Optical upper limit with Kinder observations
  73. EP260214a: Optical upper limits with Kinder observations
  74. EP260214b: EP-FXT follow-up observation
  75. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  76. EP260214b: DDOTI Optical Detection
  77. EP260214b: GROWTH-India Telescope optical upper limit
  78. EP260214a: VLT near-infrared observation
  79. EP260214a: NOT optical upper limits
  80. EP260214a: COLIBRÍ optical upper limits
  81. EP260214b: OHP/T120 optical observations
  82. EP260214a: refined analysis of the EP-FXT observation
  83. EP260214b: LCO optical counterpart detection
  84. GRB 260211A: SVOM/VT optical counterpart
  85. EP260214b: COLIBRÍ optical observations
  86. EP260214b: NOT optical counterpart detection
  87. EP260214b: Einstein Probe detection of a fast X-ray transient
  88. EP260214a: Global MASTER-Net observations report
  89. EP260214a: Einstein Probe detection of an X-ray transient
  90. GRB 260212A: AstroSat CZTI detection
  91. GRB 260212A: Fermi GBM Observation
  92. EP260213a: Liverpool Telescope optical upper limits
  93. EP260213a: Global MASTER-Net observations report
  94. EP260213a: COLIBRÍ optical upper limits
  95. EP260213a: Optical upper limits with Kinder observations
  96. EP260213a: Mondy R-band optical upper limit
  97. EP260213a: SVOM/C-GFT upper limit
  98. EP260213a: refined analysis of the EP-FXT observation
  99. EP260213a: Einstein Probe detection of a fast X-ray transient
  100. EP/WXT 01709258378: NOT optical upper limits

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