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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"

28100 results found.

  1. GRB 260303A: 1.3m DFOT optical upper limit
  2. Fermi GRB 260305A: Global MASTER-Net observations report
  3. GRB 260303B: AstroSat CZTI detection
  4. GRB 260303A: SVOM/VT optical observations
  5. GRB 260303A: J-band observations with WINTER
  6. GRB 260303B: NuSTAR detection of prompt emission
  7. EP260302a: Global MASTER-Net observations report
  8. Fermi GRB 260303B: Global MASTER-Net observations report
  9. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  10. EP260302a: analysis of the follow-up EP-FXT observation
  11. EP260302a: LCO observations
  12. EP260302a: BOOTES-7 optical counterpart detection at early times
  13. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  14. GRB 260303A: SVOM detection of a burst
  15. GRB 260228A: EP-FXT follow-up observation
  16. EP260302a: Einstein Probe detection of an X-ray transient
  17. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  18. GRB 251130B: TERI Gamma-ray detection
  19. GRB 260208A: TERI Gamma-ray detection
  20. EP260227a: Mondy optical observations
  21. GRB 260228A: CAHA 2.2m telescope optical upper limit
  22. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  23. EP260227a: Mephisto optical detection
  24. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  25. EP260227a: SVOM/VT optical observation
  26. GRB 260228A: SVOM/VT optical upper limits
  27. GRB 260225D: SVOM/GRM observation
  28. EP260227A: 3.6m DOT optical afterglow detection
  29. GRB 260225B: SVOM/GRM observation
  30. EP260227a: Liverpool Telescope optical observations
  31. EP260227a: LCOGT Optical Observations
  32. GRB 260226A: Asiago r-band upper limit
  33. EP260227a: Liverpool Telescope observations
  34. EP260227a: COLIBRÍ optical observations
  35. EP260227a: NOT optical observations
  36. EP260227a: Global MASTER-Net observations report
  37. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  38. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  39. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  40. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  41. EP260214a: VLT/FORS2 optical observations
  42. GRB 260225A: WINTER J-band upper limit
  43. GRB 260226A: COLIBRÍ optical upper limits
  44. GRB 260226A: LCOGT Optical Upper Limit
  45. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  46. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  47. GRB 260226A: Glowbug gamma-ray detection
  48. GRB 260226A: NuSTAR detection of bright prompt emission
  49. GRB 260226A : GROWTH-India Telescope optical observations
  50. GRB 260226A: LAST optical upper limit
  51. GRB 260226A: Fermi GBM observation
  52. LAT GRB260226.44: Global MASTER-Net observations report
  53. Fermi GRB 260226A: Global MASTER-Net observations report
  54. GRB 260226A: AstroSat CZTI detection of bright long burst
  55. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  56. EP260224a: LCO optical upper limits
  57. GRB 260225A: EP-FXT follow-up observation
  58. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  59. GRB 260223A: Fermi GBM Observation
  60. GRB 260225A: SVOM/VT optical upper limits
  61. EP260223a: Liverpool Telescope upper limits
  62. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  63. EP260224a: Einstein Probe detection of an X-ray transient
  64. EP 260225.148: COLIBRÍ Confirmation of flaring star
  65. EP260223a: Xinglong optical upper limit
  66. GRB 260223A: Glowbug gamma-ray detection
  67. EP260213a: Mephisto optical upper limits
  68. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  69. sb26021801: SVOM/C-GFT upper limit
  70. EP260223a: COLIBRÍ optical upper limits
  71. EP260223a: Einstein Probe detection of an X-ray transient
  72. GRB 260223A: SVOM/GRM observation
  73. GRB 260223A: COLIBRÍ further optical observations and a brightening
  74. EP260221a: Optical upper limit with Kinder observations
  75. GRB 260223A: COLIBRÍ optical observations
  76. GRB 260223A: DDOTI Optical Candidate
  77. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  78. Fermi GRB 260223A: Global MASTER-Net observations report
  79. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  80. EP260221a: COLIBRÍ optical counterpart candidate
  81. EP260221a: Gemini South z-band upper limit
  82. EP260221a: Global MASTER-Net observations report
  83. EP260221a: EP-FXT follow-up observation
  84. Fermi GRB 260221B: Global MASTER-Net observations report
  85. EP-WXT01709258519: Xinglong optical upper limit
  86. EP260221a: Xinglong optical upper limit
  87. Fermi GRB 260221A: Global MASTER-Net observations report
  88. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  89. EP260221a: GOTO optical upper limit
  90. EP260221a: COLIBRÍ optical upper limit
  91. SVOM alert sb26021801: LCO optical upper limit
  92. EP260221a: Einstein Probe detection of an X-ray transient
  93. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  94. Fermi GRB 260219A: Global MASTER-Net observations report
  95. SVOM alert sb26021801: LAST optical upper limit
  96. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  97. IceCube Alert 260217A: Global MASTER-Net observations report
  98. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  99. sb26021801: SVOM detection of a long faint X-ray transient
  100. EP-WXT 01709258455: NOT optical upper limits

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