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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 260207A: TESS Detection and Possible VLA Counterpart
  2. EP260302a: SVOM/VT optical observation
  3. EP260306a: Gemini-North redshift z = 4.773
  4. EP260306a: SVOM/VT optical observation
  5. EP260302a: Gemini-South redshift z = 1.535
  6. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  7. EP260306a: Einstein Probe detection of an X-ray transient
  8. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  9. EP260302a: Optical afterglow rebrightening
  10. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  11. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  12. GRB 260303A: 1.3m DFOT optical upper limit
  13. EP260214b: ATCA 6 GHz observations
  14. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  15. GRB 260303A: SVOM/ECLAIRs refined analysis
  16. Fermi GRB 260305A: Global MASTER-Net observations report
  17. GRB 260305A: Fermi GBM Final Real-time Localization
  18. GRB 260303B: AstroSat CZTI detection
  19. GRB 260304A: AstroSat CZTI detection of a long burst
  20. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  21. GRB 260303A: SVOM/VT optical observations
  22. GRB 260303A: J-band observations with WINTER
  23. GRB 260303B: NuSTAR detection of prompt emission
  24. EP260302a: Global MASTER-Net observations report
  25. Fermi GRB 260303B: Global MASTER-Net observations report
  26. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  27. GRB 260228A: SVOM/ECLAIRs refined analysis
  28. GRB 260225A: SVOM/ECLAIRs refined analysis
  29. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  30. GRB 260303B: Fermi GBM Final Real-time Localization
  31. EP260302a: analysis of the follow-up EP-FXT observation
  32. EP260227a: Gemini-South optical observations
  33. EP260302a: LCO observations
  34. EP260302a: BOOTES-7 optical counterpart detection at early times
  35. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  36. GRB 260303A: SVOM detection of a burst
  37. GRB 260228A: EP-FXT follow-up observation
  38. EP260302a: Einstein Probe detection of an X-ray transient
  39. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  40. GRB 251130B: TERI Gamma-ray detection
  41. GRB 260208A: TERI Gamma-ray detection
  42. GRB 260302A: Fermi GBM Final Real-time Localization
  43. EP260227a: Mondy optical observations
  44. GRB 260228A: CAHA 2.2m telescope optical upper limit
  45. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  46. EP260227a: Mephisto optical detection
  47. GRID detection of GRB 260225D
  48. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  49. EP260227a: further LCO observations
  50. EP260227a: SVOM/VT optical observation
  51. GRB 260228A: SVOM/VT optical upper limits
  52. GRB 260225D: SVOM/GRM observation
  53. EP260227A: 3.6m DOT optical afterglow detection
  54. GRB 260225B: SVOM/GRM observation
  55. GRB 260228A: SVOM detection of a burst
  56. EP260227a: FTW optical and NIR observations
  57. EP260227a: Liverpool Telescope optical observations
  58. EP260227a: LCOGT Optical Observations
  59. GRB 260226A: Asiago r-band upper limit
  60. EP260227a: Thai National Telescope observations
  61. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  62. EP260227a: Liverpool Telescope observations
  63. EP260227a: COLIBRÍ optical observations
  64. EP260227a: NOT optical observations
  65. GRB 260225A: SVOM/VT optical continued observations and upper limit
  66. GRID detection of GRB 260223A
  67. EP260227a: Global MASTER-Net observations report
  68. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  69. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  70. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  71. IceCube cascade alert 142200_1517143 retraction
  72. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  73. Konus-Wind detection of GRB 260226A
  74. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  75. EP260214a: VLT/FORS2 optical observations
  76. GRB 260225A: WINTER J-band upper limit
  77. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  78. GRB 260226A: COLIBRÍ optical upper limits
  79. GRB 260226A: LCOGT Optical Upper Limit
  80. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  81. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  82. GRB 260226A: Glowbug gamma-ray detection
  83. GRB 260226A: NuSTAR detection of bright prompt emission
  84. GRB 260226A : GROWTH-India Telescope optical observations
  85. GRB 260226A: LAST optical upper limit
  86. GRB 260226A: Fermi GBM observation
  87. GRB 260226A: Fermi-LAT refined analysis
  88. The EP-WXT trigger 01709258652 is likely a flaring star
  89. LAT GRB260226.44: Global MASTER-Net observations report
  90. Fermi GRB 260226A: Global MASTER-Net observations report
  91. GRB 260226A: AstroSat CZTI detection of bright long burst
  92. EP260214a: VLA 6 GHz detection
  93. GRB 260226A: Fermi-LAT detection of a bright burst
  94. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  95. EP260224a: LCO optical upper limits
  96. GRB260225A: SVOM/ECLAIRs refined position
  97. GRB 260226A: Fermi GBM Final Real-time Localization
  98. GRB 260225A: EP-FXT follow-up observation
  99. GRB 260225A: SVOM/VT optical observation
  100. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate

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