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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 260303A: 1.3m DFOT optical upper limit
  2. GRB 260303A: 1.3m DFOT optical upper limit
  3. EP260214b: ATCA 6 GHz observations
  4. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  5. GRB 260303A: SVOM/ECLAIRs refined analysis
  6. Fermi GRB 260305A: Global MASTER-Net observations report
  7. GRB 260305A: Fermi GBM Final Real-time Localization
  8. GRB 260303B: AstroSat CZTI detection
  9. GRB 260304A: AstroSat CZTI detection of a long burst
  10. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  11. GRB 260303A: SVOM/VT optical observations
  12. GRB 260303A: J-band observations with WINTER
  13. GRB 260303B: NuSTAR detection of prompt emission
  14. EP260302a: Global MASTER-Net observations report
  15. Fermi GRB 260303B: Global MASTER-Net observations report
  16. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  17. GRB 260228A: SVOM/ECLAIRs refined analysis
  18. GRB 260225A: SVOM/ECLAIRs refined analysis
  19. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  20. GRB 260303B: Fermi GBM Final Real-time Localization
  21. EP260302a: analysis of the follow-up EP-FXT observation
  22. EP260227a: Gemini-South optical observations
  23. EP260302a: LCO observations
  24. EP260302a: BOOTES-7 optical counterpart detection at early times
  25. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  26. GRB 260303A: SVOM detection of a burst
  27. GRB 260228A: EP-FXT follow-up observation
  28. EP260302a: Einstein Probe detection of an X-ray transient
  29. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  30. GRB 251130B: TERI Gamma-ray detection
  31. GRB 260208A: TERI Gamma-ray detection
  32. GRB 260302A: Fermi GBM Final Real-time Localization
  33. EP260227a: Mondy optical observations
  34. GRB 260228A: CAHA 2.2m telescope optical upper limit
  35. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  36. EP260227a: Mephisto optical detection
  37. GRID detection of GRB 260225D
  38. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  39. EP260227a: further LCO observations
  40. EP260227a: SVOM/VT optical observation
  41. GRB 260228A: SVOM/VT optical upper limits
  42. GRB 260225D: SVOM/GRM observation
  43. EP260227A: 3.6m DOT optical afterglow detection
  44. GRB 260225B: SVOM/GRM observation
  45. GRB 260228A: SVOM detection of a burst
  46. EP260227a: FTW optical and NIR observations
  47. EP260227a: Liverpool Telescope optical observations
  48. EP260227a: LCOGT Optical Observations
  49. GRB 260226A: Asiago r-band upper limit
  50. EP260227a: Thai National Telescope observations
  51. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  52. EP260227a: Liverpool Telescope observations
  53. EP260227a: COLIBRÍ optical observations
  54. EP260227a: NOT optical observations
  55. GRB 260225A: SVOM/VT optical continued observations and upper limit
  56. GRID detection of GRB 260223A
  57. EP260227a: Global MASTER-Net observations report
  58. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  59. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  60. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  61. IceCube cascade alert 142200_1517143 retraction
  62. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  63. Konus-Wind detection of GRB 260226A
  64. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  65. EP260214a: VLT/FORS2 optical observations
  66. GRB 260225A: WINTER J-band upper limit
  67. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  68. GRB 260226A: COLIBRÍ optical upper limits
  69. GRB 260226A: LCOGT Optical Upper Limit
  70. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  71. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  72. GRB 260226A: Glowbug gamma-ray detection
  73. GRB 260226A: NuSTAR detection of bright prompt emission
  74. GRB 260226A : GROWTH-India Telescope optical observations
  75. GRB 260226A: LAST optical upper limit
  76. GRB 260226A: Fermi GBM observation
  77. GRB 260226A: Fermi-LAT refined analysis
  78. The EP-WXT trigger 01709258652 is likely a flaring star
  79. LAT GRB260226.44: Global MASTER-Net observations report
  80. Fermi GRB 260226A: Global MASTER-Net observations report
  81. GRB 260226A: AstroSat CZTI detection of bright long burst
  82. EP260214a: VLA 6 GHz detection
  83. GRB 260226A: Fermi-LAT detection of a bright burst
  84. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  85. EP260224a: LCO optical upper limits
  86. GRB260225A: SVOM/ECLAIRs refined position
  87. GRB 260226A: Fermi GBM Final Real-time Localization
  88. GRB 260225A: EP-FXT follow-up observation
  89. GRB 260225A: SVOM/VT optical observation
  90. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  91. GRB 260225C: Fermi GBM Final Real-time Localization
  92. GRB 260223A: Fermi GBM Observation
  93. GRB 260225A: SVOM/VT optical upper limits
  94. GRB 260225B: Fermi GBM Final Real-time Localization
  95. EP260126a: VLA 6 GHz detection
  96. EP260223a: Liverpool Telescope upper limits
  97. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  98. GRB 260225A: SVOM detection of a burst
  99. EP260224a: Einstein Probe detection of an X-ray transient
  100. EP 260225.148: COLIBRÍ Confirmation of flaring star

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