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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"

31634 results found.

  1. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  2. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  3. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  4. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  5. GRB260310A / AT2026fgk: P200 Spectroscopy
  6. GRB 260312B: Glowbug gamma-ray detection
  7. GRB 260310A: Fermi GBM Observation
  8. GRB 260310A: potential optical counterpart
  9. Fermi GRB 260312B: Global MASTER-Net observations report
  10. Fermi GRB 260311B: Global MASTER-Net observations report
  11. GRB 260310B: GECAM-B observation of a burst
  12. Retraction of GCN 43965: GRB is actually solar flare
  13. GRB 260131A/B: radio detection with the VLA
  14. EP260302a: MeerKAT radio counterpart
  15. GRB260307A: GECAM-B observation of a burst
  16. GRB 260308A: SVOM/GRM observation of a short GRB
  17. EP260306a: Mondy optical upper limit
  18. GRB 260310A: AstroSat CZTI detection of a long burst
  19. Fermi GRB 260310B: Global MASTER-Net observations report
  20. Fermi GRB 260310A: Global MASTER-Net observations report
  21. GRB 260307B: SVOM/ECLAIRs refined analysis
  22. GRB 260208A: radio detection with the VLA
  23. GRB 260307A: Glowbug gamma-ray detection
  24. Fermi GBM Sub-Threshold Detection of GRB 260307B
  25. GRB 260307B: Mephisto optical upper limits
  26. GRB 260307B: possible NOT optical counterpart
  27. GRB 260307B: SVOM/VT upper limit with X band data analysis
  28. Fermi GRB 260307A: Global MASTER-Net observations report
  29. GRB260307B: GROWTH-India Telescope optical upper limit
  30. GRB 260307B: SVOM/VT optical candidate
  31. GRB 260307B: SVOM/C-GFT upper limit
  32. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  33. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 260207A: TESS Detection and Possible VLA Counterpart
  35. EP260302a: SVOM/VT optical observation
  36. EP260306a: Gemini-North redshift z = 4.773
  37. EP260306a: SVOM/VT optical observation
  38. EP260302a: Gemini-South redshift z = 1.535
  39. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  40. EP260306a: Einstein Probe detection of an X-ray transient
  41. EP260302a: Optical afterglow rebrightening
  42. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  43. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  44. GRB 260303A: 1.3m DFOT optical upper limit
  45. EP260214b: ATCA 6 GHz observations
  46. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  47. GRB 260303A: SVOM/ECLAIRs refined analysis
  48. Fermi GRB 260305A: Global MASTER-Net observations report
  49. GRB 260303B: AstroSat CZTI detection
  50. GRB 260303A: SVOM/VT optical observations
  51. GRB 260303A: J-band observations with WINTER
  52. GRB 260303B: NuSTAR detection of prompt emission
  53. EP260302a: Global MASTER-Net observations report
  54. Fermi GRB 260303B: Global MASTER-Net observations report
  55. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  56. GRB 260228A: SVOM/ECLAIRs refined analysis
  57. GRB 260225A: SVOM/ECLAIRs refined analysis
  58. EP260302a: analysis of the follow-up EP-FXT observation
  59. EP260227a: Gemini-South optical observations
  60. EP260302a: LCO observations
  61. EP260302a: BOOTES-7 optical counterpart detection at early times
  62. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  63. GRB 260228A: EP-FXT follow-up observation
  64. GRB 251130B: TERI Gamma-ray detection
  65. GRB 260208A: TERI Gamma-ray detection
  66. EP260227a: Mondy optical observations
  67. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. EP260227a: Mephisto optical detection
  69. GRID detection of GRB 260225D
  70. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  71. EP260227a: further LCO observations
  72. EP260227a: SVOM/VT optical observation
  73. GRB 260228A: SVOM/VT optical upper limits
  74. GRB 260225D: SVOM/GRM observation
  75. EP260227A: 3.6m DOT optical afterglow detection
  76. GRB 260225B: SVOM/GRM observation
  77. EP260227a: FTW optical and NIR observations
  78. EP260227a: Liverpool Telescope optical observations
  79. EP260227a: LCOGT Optical Observations
  80. GRB 260226A: Asiago r-band upper limit
  81. EP260227a: Thai National Telescope observations
  82. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  83. EP260227a: Liverpool Telescope observations
  84. EP260227a: COLIBRÍ optical observations
  85. EP260227a: NOT optical observations
  86. GRB 260225A: SVOM/VT optical continued observations and upper limit
  87. GRID detection of GRB 260223A
  88. EP260227a: Global MASTER-Net observations report
  89. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  90. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  91. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  92. Konus-Wind detection of GRB 260226A
  93. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  94. EP260214a: VLT/FORS2 optical observations
  95. GRB 260225A: WINTER J-band upper limit
  96. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  97. GRB 260226A: COLIBRÍ optical upper limits
  98. GRB 260226A: LCOGT Optical Upper Limit
  99. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  100. GRB 260226A: Glowbug gamma-ray detection

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