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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"

24278 results found.

  1. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  2. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  3. EP260316a: Xinglong optical upper limit
  4. GRB 260316B: Fermi GBM Final Real-time Localization
  5. EP260316a: optical upper limit with Kinder observations
  6. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  7. GRB 260314A: Glowbug gamma-ray detection
  8. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  9. EP260314a: Xinglong optical upper limit
  10. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  11. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  12. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  13. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP260314a: Global MASTER-Net observations report
  15. EP260314a: SVOM/VT optical candidate
  16. Fermi trigger No 795185313: Global MASTER-Net observations report
  17. IceCube Alert 260315A: Global MASTER-Net observations report
  18. GRB 260310A / AT2026fgk: TNG NIR detection
  19. Fermi GRB 260314A: Global MASTER-Net observations report
  20. Fermi GRB 260313A: Global MASTER-Net observations report
  21. GRB 260314A: Fermi GBM Final Real-time Localization
  22. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  23. GRB 260313A: A Correction to the Fermi GBM Final Localization
  24. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  25. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  26. GRB 260313A: Fermi GBM Final Real-time Localization
  27. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  28. GRB260310A / AT2026fgk: P200 Spectroscopy
  29. GRB 260310A: Fermi GBM Observation
  30. GRB 260310A: potential optical counterpart
  31. Fermi GRB 260312B: Global MASTER-Net observations report
  32. Fermi GRB 260311B: Global MASTER-Net observations report
  33. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  34. GRB 260312B: Fermi GBM Final Real-time Localization
  35. The EP-WXT trigger 01709258843 is not a real source
  36. GRB 260311B: Fermi GBM Final Real-time Localization
  37. EP260302a: MeerKAT radio counterpart
  38. GRB 260308A: SVOM/GRM observation of a short GRB
  39. GRB 260311A: Fermi GBM Final Real-time Localization
  40. Fermi GRB 260310B: Global MASTER-Net observations report
  41. GRB 260310B: Fermi GBM Final Real-time Localization
  42. Fermi GRB 260310A: Global MASTER-Net observations report
  43. GRB 260307B: SVOM/ECLAIRs refined analysis
  44. GRB 260310A: Fermi GBM Final Real-time Localization
  45. GRB 260308A: Fermi GBM Final Real-time Localization
  46. Fermi GBM Sub-Threshold Detection of GRB 260307B
  47. GRB 260307B: Mephisto optical upper limits
  48. GRB 260307B: possible NOT optical counterpart
  49. GRB 260307B: SVOM/VT upper limit with X band data analysis
  50. Fermi GRB 260307A: Global MASTER-Net observations report
  51. GRB260307B: GROWTH-India Telescope optical upper limit
  52. GRB 260307B: SVOM/VT optical candidate
  53. GRB 260307B: SVOM/C-GFT upper limit
  54. GRB 260307B: SVOM detection of a burst
  55. GRB 260307A: Fermi GBM Final Localization
  56. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  57. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  58. GRB 260207A: TESS Detection and Possible VLA Counterpart
  59. EP260302a: SVOM/VT optical observation
  60. EP260306a: Gemini-North redshift z = 4.773
  61. EP260306a: SVOM/VT optical observation
  62. EP260302a: Gemini-South redshift z = 1.535
  63. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  64. GRB 260303A: 1.3m DFOT optical upper limit
  65. GRB 260303A: SVOM/ECLAIRs refined analysis
  66. Fermi GRB 260305A: Global MASTER-Net observations report
  67. GRB 260305A: Fermi GBM Final Real-time Localization
  68. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  69. GRB 260303A: SVOM/VT optical observations
  70. GRB 260303B: NuSTAR detection of prompt emission
  71. EP260302a: Global MASTER-Net observations report
  72. Fermi GRB 260303B: Global MASTER-Net observations report
  73. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  74. GRB 260228A: SVOM/ECLAIRs refined analysis
  75. GRB 260225A: SVOM/ECLAIRs refined analysis
  76. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  77. GRB 260303B: Fermi GBM Final Real-time Localization
  78. EP260302a: BOOTES-7 optical counterpart detection at early times
  79. GRB 260303A: SVOM detection of a burst
  80. GRB 260228A: EP-FXT follow-up observation
  81. GRB 260302A: Fermi GBM Final Real-time Localization
  82. EP260227a: Mephisto optical detection
  83. EP260227a: SVOM/VT optical observation
  84. GRB 260228A: SVOM/VT optical upper limits
  85. GRB 260225D: SVOM/GRM observation
  86. EP260227A: 3.6m DOT optical afterglow detection
  87. GRB 260225B: SVOM/GRM observation
  88. GRB 260228A: SVOM detection of a burst
  89. EP260227a: LCOGT Optical Observations
  90. GRB 260226A: Asiago r-band upper limit
  91. EP260227a: Thai National Telescope observations
  92. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  93. GRB 260225A: SVOM/VT optical continued observations and upper limit
  94. EP260227a: Global MASTER-Net observations report
  95. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  96. IceCube cascade alert 142200_1517143 retraction
  97. Konus-Wind detection of GRB 260226A
  98. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  99. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  100. GRB 260226A: LCOGT Optical Upper Limit

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