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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"

28055 results found.

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

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