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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"

24281 results found.

  1. GRB 260316B: SVOM/GRM observation
  2. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  3. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  4. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  5. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  6. EP260316a: Xinglong optical upper limit
  7. GRB 260316B: Fermi GBM Final Real-time Localization
  8. EP260316a: optical upper limit with Kinder observations
  9. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  10. GRB 260314A: Glowbug gamma-ray detection
  11. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  12. EP260314a: Xinglong optical upper limit
  13. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  14. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  15. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  16. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  17. EP260314a: Global MASTER-Net observations report
  18. EP260314a: SVOM/VT optical candidate
  19. Fermi trigger No 795185313: Global MASTER-Net observations report
  20. IceCube Alert 260315A: Global MASTER-Net observations report
  21. GRB 260310A / AT2026fgk: TNG NIR detection
  22. Fermi GRB 260314A: Global MASTER-Net observations report
  23. Fermi GRB 260313A: Global MASTER-Net observations report
  24. GRB 260314A: Fermi GBM Final Real-time Localization
  25. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  26. GRB 260313A: A Correction to the Fermi GBM Final Localization
  27. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  28. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  29. GRB 260313A: Fermi GBM Final Real-time Localization
  30. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  31. GRB260310A / AT2026fgk: P200 Spectroscopy
  32. GRB 260310A: Fermi GBM Observation
  33. GRB 260310A: potential optical counterpart
  34. Fermi GRB 260312B: Global MASTER-Net observations report
  35. Fermi GRB 260311B: Global MASTER-Net observations report
  36. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  37. GRB 260312B: Fermi GBM Final Real-time Localization
  38. The EP-WXT trigger 01709258843 is not a real source
  39. GRB 260311B: Fermi GBM Final Real-time Localization
  40. EP260302a: MeerKAT radio counterpart
  41. GRB 260308A: SVOM/GRM observation of a short GRB
  42. GRB 260311A: Fermi GBM Final Real-time Localization
  43. Fermi GRB 260310B: Global MASTER-Net observations report
  44. GRB 260310B: Fermi GBM Final Real-time Localization
  45. Fermi GRB 260310A: Global MASTER-Net observations report
  46. GRB 260307B: SVOM/ECLAIRs refined analysis
  47. GRB 260310A: Fermi GBM Final Real-time Localization
  48. GRB 260308A: Fermi GBM Final Real-time Localization
  49. Fermi GBM Sub-Threshold Detection of GRB 260307B
  50. GRB 260307B: Mephisto optical upper limits
  51. GRB 260307B: possible NOT optical counterpart
  52. GRB 260307B: SVOM/VT upper limit with X band data analysis
  53. Fermi GRB 260307A: Global MASTER-Net observations report
  54. GRB260307B: GROWTH-India Telescope optical upper limit
  55. GRB 260307B: SVOM/VT optical candidate
  56. GRB 260307B: SVOM/C-GFT upper limit
  57. GRB 260307B: SVOM detection of a burst
  58. GRB 260307A: Fermi GBM Final Localization
  59. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  60. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  61. GRB 260207A: TESS Detection and Possible VLA Counterpart
  62. EP260302a: SVOM/VT optical observation
  63. EP260306a: Gemini-North redshift z = 4.773
  64. EP260306a: SVOM/VT optical observation
  65. EP260302a: Gemini-South redshift z = 1.535
  66. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  67. GRB 260303A: 1.3m DFOT optical upper limit
  68. GRB 260303A: SVOM/ECLAIRs refined analysis
  69. Fermi GRB 260305A: Global MASTER-Net observations report
  70. GRB 260305A: Fermi GBM Final Real-time Localization
  71. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  72. GRB 260303A: SVOM/VT optical observations
  73. GRB 260303B: NuSTAR detection of prompt emission
  74. EP260302a: Global MASTER-Net observations report
  75. Fermi GRB 260303B: Global MASTER-Net observations report
  76. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  77. GRB 260228A: SVOM/ECLAIRs refined analysis
  78. GRB 260225A: SVOM/ECLAIRs refined analysis
  79. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  80. GRB 260303B: Fermi GBM Final Real-time Localization
  81. EP260302a: BOOTES-7 optical counterpart detection at early times
  82. GRB 260303A: SVOM detection of a burst
  83. GRB 260228A: EP-FXT follow-up observation
  84. GRB 260302A: Fermi GBM Final Real-time Localization
  85. EP260227a: Mephisto optical detection
  86. EP260227a: SVOM/VT optical observation
  87. GRB 260228A: SVOM/VT optical upper limits
  88. GRB 260225D: SVOM/GRM observation
  89. EP260227A: 3.6m DOT optical afterglow detection
  90. GRB 260225B: SVOM/GRM observation
  91. GRB 260228A: SVOM detection of a burst
  92. EP260227a: LCOGT Optical Observations
  93. GRB 260226A: Asiago r-band upper limit
  94. EP260227a: Thai National Telescope observations
  95. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  96. GRB 260225A: SVOM/VT optical continued observations and upper limit
  97. EP260227a: Global MASTER-Net observations report
  98. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  99. IceCube cascade alert 142200_1517143 retraction
  100. Konus-Wind detection of GRB 260226A

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