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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 260307B: SVOM/ECLAIRs refined analysis
  2. GRB 260208A: radio detection with the VLA
  3. GRB 260310A: Fermi GBM Final Real-time Localization
  4. GRB 260307A: Glowbug gamma-ray detection
  5. GRB 260308A: Fermi GBM Final Real-time Localization
  6. Fermi GBM Sub-Threshold Detection of GRB 260307B
  7. GRB 260307B: Mephisto optical upper limits
  8. GRB 260307B: possible NOT optical counterpart
  9. GRB 260307B: SVOM/VT upper limit with X band data analysis
  10. Fermi GRB 260307A: Global MASTER-Net observations report
  11. GRB260307B: GROWTH-India Telescope optical upper limit
  12. GRB 260307B: SVOM/VT optical candidate
  13. GRB 260307B: SVOM/C-GFT upper limit
  14. GRB 260307B: SVOM detection of a burst
  15. GRB 260307A: Fermi GBM Final Localization
  16. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  17. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 260207A: TESS Detection and Possible VLA Counterpart
  19. EP260302a: SVOM/VT optical observation
  20. EP260306a: Gemini-North redshift z = 4.773
  21. EP260306a: SVOM/VT optical observation
  22. EP260302a: Gemini-South redshift z = 1.535
  23. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  24. EP260306a: Einstein Probe detection of an X-ray transient
  25. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  26. EP260302a: Optical afterglow rebrightening
  27. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  28. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  29. GRB 260303A: 1.3m DFOT optical upper limit
  30. EP260214b: ATCA 6 GHz observations
  31. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  32. GRB 260303A: SVOM/ECLAIRs refined analysis
  33. Fermi GRB 260305A: Global MASTER-Net observations report
  34. GRB 260305A: Fermi GBM Final Real-time Localization
  35. GRB 260303B: AstroSat CZTI detection
  36. GRB 260304A: AstroSat CZTI detection of a long burst
  37. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  38. GRB 260303A: SVOM/VT optical observations
  39. GRB 260303A: J-band observations with WINTER
  40. GRB 260303B: NuSTAR detection of prompt emission
  41. EP260302a: Global MASTER-Net observations report
  42. Fermi GRB 260303B: Global MASTER-Net observations report
  43. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  44. GRB 260228A: SVOM/ECLAIRs refined analysis
  45. GRB 260225A: SVOM/ECLAIRs refined analysis
  46. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  47. GRB 260303B: Fermi GBM Final Real-time Localization
  48. EP260302a: analysis of the follow-up EP-FXT observation
  49. EP260227a: Gemini-South optical observations
  50. EP260302a: LCO observations
  51. EP260302a: BOOTES-7 optical counterpart detection at early times
  52. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  53. GRB 260303A: SVOM detection of a burst
  54. GRB 260228A: EP-FXT follow-up observation
  55. EP260302a: Einstein Probe detection of an X-ray transient
  56. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  57. GRB 251130B: TERI Gamma-ray detection
  58. GRB 260208A: TERI Gamma-ray detection
  59. GRB 260302A: Fermi GBM Final Real-time Localization
  60. EP260227a: Mondy optical observations
  61. GRB 260228A: CAHA 2.2m telescope optical upper limit
  62. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  63. EP260227a: Mephisto optical detection
  64. GRID detection of GRB 260225D
  65. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  66. EP260227a: further LCO observations
  67. EP260227a: SVOM/VT optical observation
  68. GRB 260228A: SVOM/VT optical upper limits
  69. GRB 260225D: SVOM/GRM observation
  70. EP260227A: 3.6m DOT optical afterglow detection
  71. GRB 260225B: SVOM/GRM observation
  72. GRB 260228A: SVOM detection of a burst
  73. EP260227a: FTW optical and NIR observations
  74. EP260227a: Liverpool Telescope optical observations
  75. EP260227a: LCOGT Optical Observations
  76. GRB 260226A: Asiago r-band upper limit
  77. EP260227a: Thai National Telescope observations
  78. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  79. EP260227a: Liverpool Telescope observations
  80. EP260227a: COLIBRÍ optical observations
  81. EP260227a: NOT optical observations
  82. GRB 260225A: SVOM/VT optical continued observations and upper limit
  83. GRID detection of GRB 260223A
  84. EP260227a: Global MASTER-Net observations report
  85. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  86. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  87. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  88. IceCube cascade alert 142200_1517143 retraction
  89. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  90. Konus-Wind detection of GRB 260226A
  91. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  92. EP260214a: VLT/FORS2 optical observations
  93. GRB 260225A: WINTER J-band upper limit
  94. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  95. GRB 260226A: COLIBRÍ optical upper limits
  96. GRB 260226A: LCOGT Optical Upper Limit
  97. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  98. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  99. GRB 260226A: Glowbug gamma-ray detection
  100. GRB 260226A: NuSTAR detection of bright prompt emission

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