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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"
  1. GRB 260310A: AstroSat CZTI detection of a long burst
  2. GRB 260311A: Fermi GBM Final Real-time Localization
  3. Fermi GRB 260310B: Global MASTER-Net observations report
  4. GRB 260310B: Fermi GBM Final Real-time Localization
  5. Fermi GRB 260310A: Global MASTER-Net observations report
  6. GRB 260307B: SVOM/ECLAIRs refined analysis
  7. GRB 260208A: radio detection with the VLA
  8. GRB 260310A: Fermi GBM Final Real-time Localization
  9. GRB 260307A: Glowbug gamma-ray detection
  10. GRB 260308A: Fermi GBM Final Real-time Localization
  11. Fermi GBM Sub-Threshold Detection of GRB 260307B
  12. GRB 260307B: Mephisto optical upper limits
  13. GRB 260307B: possible NOT optical counterpart
  14. GRB 260307B: SVOM/VT upper limit with X band data analysis
  15. Fermi GRB 260307A: Global MASTER-Net observations report
  16. GRB260307B: GROWTH-India Telescope optical upper limit
  17. GRB 260307B: SVOM/VT optical candidate
  18. GRB 260307B: SVOM/C-GFT upper limit
  19. GRB 260307B: SVOM detection of a burst
  20. GRB 260307A: Fermi GBM Final Localization
  21. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  22. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  23. GRB 260207A: TESS Detection and Possible VLA Counterpart
  24. EP260302a: SVOM/VT optical observation
  25. EP260306a: Gemini-North redshift z = 4.773
  26. EP260306a: SVOM/VT optical observation
  27. EP260302a: Gemini-South redshift z = 1.535
  28. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  29. EP260306a: Einstein Probe detection of an X-ray transient
  30. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  31. EP260302a: Optical afterglow rebrightening
  32. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  33. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  34. GRB 260303A: 1.3m DFOT optical upper limit
  35. EP260214b: ATCA 6 GHz observations
  36. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  37. GRB 260303A: SVOM/ECLAIRs refined analysis
  38. Fermi GRB 260305A: Global MASTER-Net observations report
  39. GRB 260305A: Fermi GBM Final Real-time Localization
  40. GRB 260303B: AstroSat CZTI detection
  41. GRB 260304A: AstroSat CZTI detection of a long burst
  42. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  43. GRB 260303A: SVOM/VT optical observations
  44. GRB 260303A: J-band observations with WINTER
  45. GRB 260303B: NuSTAR detection of prompt emission
  46. EP260302a: Global MASTER-Net observations report
  47. Fermi GRB 260303B: Global MASTER-Net observations report
  48. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  49. GRB 260228A: SVOM/ECLAIRs refined analysis
  50. GRB 260225A: SVOM/ECLAIRs refined analysis
  51. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  52. GRB 260303B: Fermi GBM Final Real-time Localization
  53. EP260302a: analysis of the follow-up EP-FXT observation
  54. EP260227a: Gemini-South optical observations
  55. EP260302a: LCO observations
  56. EP260302a: BOOTES-7 optical counterpart detection at early times
  57. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  58. GRB 260303A: SVOM detection of a burst
  59. GRB 260228A: EP-FXT follow-up observation
  60. EP260302a: Einstein Probe detection of an X-ray transient
  61. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  62. GRB 251130B: TERI Gamma-ray detection
  63. GRB 260208A: TERI Gamma-ray detection
  64. GRB 260302A: Fermi GBM Final Real-time Localization
  65. EP260227a: Mondy optical observations
  66. GRB 260228A: CAHA 2.2m telescope optical upper limit
  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. GRB 260228A: SVOM detection of a burst
  78. EP260227a: FTW optical and NIR observations
  79. EP260227a: Liverpool Telescope optical observations
  80. EP260227a: LCOGT Optical Observations
  81. GRB 260226A: Asiago r-band upper limit
  82. EP260227a: Thai National Telescope observations
  83. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  84. EP260227a: Liverpool Telescope observations
  85. EP260227a: COLIBRÍ optical observations
  86. EP260227a: NOT optical observations
  87. GRB 260225A: SVOM/VT optical continued observations and upper limit
  88. GRID detection of GRB 260223A
  89. EP260227a: Global MASTER-Net observations report
  90. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  91. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  92. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  93. IceCube cascade alert 142200_1517143 retraction
  94. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  95. Konus-Wind detection of GRB 260226A
  96. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  97. EP260214a: VLT/FORS2 optical observations
  98. GRB 260225A: WINTER J-band upper limit
  99. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  100. GRB 260226A: COLIBRÍ optical upper limits

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