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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"

23661 results found.

  1. GRB 260310A / AT2026fgk: TNG NIR detection
  2. Fermi GRB 260314A: Global MASTER-Net observations report
  3. Fermi GRB 260313A: Global MASTER-Net observations report
  4. GRB 260314A: Fermi GBM Final Real-time Localization
  5. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  6. GRB 260313A: A Correction to the Fermi GBM Final Localization
  7. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  8. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  9. GRB 260313A: Fermi GBM Final Real-time Localization
  10. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  11. GRB260310A / AT2026fgk: P200 Spectroscopy
  12. GRB 260310A: Fermi GBM Observation
  13. GRB 260310A: potential optical counterpart
  14. Fermi GRB 260312B: Global MASTER-Net observations report
  15. Fermi GRB 260311B: Global MASTER-Net observations report
  16. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  17. GRB 260312B: Fermi GBM Final Real-time Localization
  18. The EP-WXT trigger 01709258843 is not a real source
  19. GRB 260311B: Fermi GBM Final Real-time Localization
  20. EP260302a: MeerKAT radio counterpart
  21. GRB 260308A: SVOM/GRM observation of a short GRB
  22. GRB 260311A: Fermi GBM Final Real-time Localization
  23. Fermi GRB 260310B: Global MASTER-Net observations report
  24. GRB 260310B: Fermi GBM Final Real-time Localization
  25. Fermi GRB 260310A: Global MASTER-Net observations report
  26. GRB 260307B: SVOM/ECLAIRs refined analysis
  27. GRB 260310A: Fermi GBM Final Real-time Localization
  28. GRB 260308A: Fermi GBM Final Real-time Localization
  29. Fermi GBM Sub-Threshold Detection of GRB 260307B
  30. GRB 260307B: Mephisto optical upper limits
  31. GRB 260307B: possible NOT optical counterpart
  32. GRB 260307B: SVOM/VT upper limit with X band data analysis
  33. Fermi GRB 260307A: Global MASTER-Net observations report
  34. GRB260307B: GROWTH-India Telescope optical upper limit
  35. GRB 260307B: SVOM/VT optical candidate
  36. GRB 260307B: SVOM/C-GFT upper limit
  37. GRB 260307B: SVOM detection of a burst
  38. GRB 260307A: Fermi GBM Final Localization
  39. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  40. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  41. GRB 260207A: TESS Detection and Possible VLA Counterpart
  42. EP260302a: SVOM/VT optical observation
  43. EP260306a: Gemini-North redshift z = 4.773
  44. EP260306a: SVOM/VT optical observation
  45. EP260302a: Gemini-South redshift z = 1.535
  46. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  47. GRB 260303A: 1.3m DFOT optical upper limit
  48. GRB 260303A: SVOM/ECLAIRs refined analysis
  49. Fermi GRB 260305A: Global MASTER-Net observations report
  50. GRB 260305A: Fermi GBM Final Real-time Localization
  51. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  52. GRB 260303A: SVOM/VT optical observations
  53. GRB 260303B: NuSTAR detection of prompt emission
  54. EP260302a: Global MASTER-Net observations report
  55. Fermi GRB 260303B: Global MASTER-Net observations report
  56. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  57. GRB 260228A: SVOM/ECLAIRs refined analysis
  58. GRB 260225A: SVOM/ECLAIRs refined analysis
  59. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  60. GRB 260303B: Fermi GBM Final Real-time Localization
  61. EP260302a: BOOTES-7 optical counterpart detection at early times
  62. GRB 260303A: SVOM detection of a burst
  63. GRB 260228A: EP-FXT follow-up observation
  64. GRB 260302A: Fermi GBM Final Real-time Localization
  65. EP260227a: Mephisto optical detection
  66. EP260227a: SVOM/VT optical observation
  67. GRB 260228A: SVOM/VT optical upper limits
  68. GRB 260225D: SVOM/GRM observation
  69. EP260227A: 3.6m DOT optical afterglow detection
  70. GRB 260225B: SVOM/GRM observation
  71. GRB 260228A: SVOM detection of a burst
  72. EP260227a: LCOGT Optical Observations
  73. GRB 260226A: Asiago r-band upper limit
  74. EP260227a: Thai National Telescope observations
  75. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  76. GRB 260225A: SVOM/VT optical continued observations and upper limit
  77. EP260227a: Global MASTER-Net observations report
  78. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  79. IceCube cascade alert 142200_1517143 retraction
  80. Konus-Wind detection of GRB 260226A
  81. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  82. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  83. GRB 260226A: LCOGT Optical Upper Limit
  84. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  85. GRB 260226A: Glowbug gamma-ray detection
  86. GRB 260226A: NuSTAR detection of bright prompt emission
  87. GRB 260226A : GROWTH-India Telescope optical observations
  88. GRB 260226A: Fermi GBM observation
  89. GRB 260226A: Fermi-LAT refined analysis
  90. The EP-WXT trigger 01709258652 is likely a flaring star
  91. LAT GRB260226.44: Global MASTER-Net observations report
  92. Fermi GRB 260226A: Global MASTER-Net observations report
  93. GRB 260226A: Fermi-LAT detection of a bright burst
  94. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  95. GRB 260226A: Fermi GBM Final Real-time Localization
  96. GRB 260225A: EP-FXT follow-up observation
  97. GRB 260225A: SVOM/VT optical observation
  98. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  99. GRB 260225C: Fermi GBM Final Real-time Localization
  100. GRB 260223A: Fermi GBM Observation

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