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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"

31737 results found.

  1. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  2. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  3. GRB 260308A: Insight-HXMT/HE detection
  4. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  5. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  6. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  7. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  8. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  9. GRB260310A / AT2026fgk: P200 Spectroscopy
  10. GRB 260312B: Glowbug gamma-ray detection
  11. GRB 260310A: Fermi GBM Observation
  12. GRB 260310A: potential optical counterpart
  13. Fermi GRB 260312B: Global MASTER-Net observations report
  14. Fermi GRB 260311B: Global MASTER-Net observations report
  15. GRB 260310B: GECAM-B observation of a burst
  16. Retraction of GCN 43965: GRB is actually solar flare
  17. GRB 260131A/B: radio detection with the VLA
  18. EP260302a: MeerKAT radio counterpart
  19. GRB260307A: GECAM-B observation of a burst
  20. GRB 260308A: SVOM/GRM observation of a short GRB
  21. EP260306a: Mondy optical upper limit
  22. GRB 260310A: AstroSat CZTI detection of a long burst
  23. Fermi GRB 260310B: Global MASTER-Net observations report
  24. Fermi GRB 260310A: Global MASTER-Net observations report
  25. GRB 260307B: SVOM/ECLAIRs refined analysis
  26. GRB 260208A: radio detection with the VLA
  27. GRB 260307A: Glowbug gamma-ray detection
  28. Fermi GBM Sub-Threshold Detection of GRB 260307B
  29. GRB 260307B: Mephisto optical upper limits
  30. GRB 260307B: possible NOT optical counterpart
  31. GRB 260307B: SVOM/VT upper limit with X band data analysis
  32. Fermi GRB 260307A: Global MASTER-Net observations report
  33. GRB260307B: GROWTH-India Telescope optical upper limit
  34. GRB 260307B: SVOM/VT optical candidate
  35. GRB 260307B: SVOM/C-GFT upper limit
  36. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  37. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  38. GRB 260207A: TESS Detection and Possible VLA Counterpart
  39. EP260302a: SVOM/VT optical observation
  40. EP260306a: Gemini-North redshift z = 4.773
  41. EP260306a: SVOM/VT optical observation
  42. EP260302a: Gemini-South redshift z = 1.535
  43. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  44. EP260306a: Einstein Probe detection of an X-ray transient
  45. EP260302a: Optical afterglow rebrightening
  46. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  47. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  48. GRB 260303A: 1.3m DFOT optical upper limit
  49. EP260214b: ATCA 6 GHz observations
  50. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  51. GRB 260303A: SVOM/ECLAIRs refined analysis
  52. Fermi GRB 260305A: Global MASTER-Net observations report
  53. GRB 260303B: AstroSat CZTI detection
  54. GRB 260303A: SVOM/VT optical observations
  55. GRB 260303A: J-band observations with WINTER
  56. GRB 260303B: NuSTAR detection of prompt emission
  57. EP260302a: Global MASTER-Net observations report
  58. Fermi GRB 260303B: Global MASTER-Net observations report
  59. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  60. GRB 260228A: SVOM/ECLAIRs refined analysis
  61. GRB 260225A: SVOM/ECLAIRs refined analysis
  62. EP260302a: analysis of the follow-up EP-FXT observation
  63. EP260227a: Gemini-South optical observations
  64. EP260302a: LCO observations
  65. EP260302a: BOOTES-7 optical counterpart detection at early times
  66. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  67. GRB 260228A: EP-FXT follow-up observation
  68. GRB 251130B: TERI Gamma-ray detection
  69. GRB 260208A: TERI Gamma-ray detection
  70. EP260227a: Mondy optical observations
  71. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  72. EP260227a: Mephisto optical detection
  73. GRID detection of GRB 260225D
  74. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  75. EP260227a: further LCO observations
  76. EP260227a: SVOM/VT optical observation
  77. GRB 260228A: SVOM/VT optical upper limits
  78. GRB 260225D: SVOM/GRM observation
  79. EP260227A: 3.6m DOT optical afterglow detection
  80. GRB 260225B: SVOM/GRM observation
  81. EP260227a: FTW optical and NIR observations
  82. EP260227a: Liverpool Telescope optical observations
  83. EP260227a: LCOGT Optical Observations
  84. GRB 260226A: Asiago r-band upper limit
  85. EP260227a: Thai National Telescope observations
  86. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  87. EP260227a: Liverpool Telescope observations
  88. EP260227a: COLIBRÍ optical observations
  89. EP260227a: NOT optical observations
  90. GRB 260225A: SVOM/VT optical continued observations and upper limit
  91. GRID detection of GRB 260223A
  92. EP260227a: Global MASTER-Net observations report
  93. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  94. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  95. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  96. Konus-Wind detection of GRB 260226A
  97. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  98. EP260214a: VLT/FORS2 optical observations
  99. GRB 260225A: WINTER J-band upper limit
  100. GRB 260226A: CALET Gamma-Ray Burst Monitor detection

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