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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"

27329 results found.

  1. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  2. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  3. GRB 260312B: Glowbug gamma-ray detection
  4. GRB 260310A: Fermi GBM Observation
  5. GRB 260310A: potential optical counterpart
  6. Fermi GRB 260312B: Global MASTER-Net observations report
  7. Fermi GRB 260311B: Global MASTER-Net observations report
  8. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  9. GRB 260131A/B: radio detection with the VLA
  10. EP260302a: MeerKAT radio counterpart
  11. GRB 260308A: SVOM/GRM observation of a short GRB
  12. EP260306a: Mondy optical upper limit
  13. Fermi GRB 260310B: Global MASTER-Net observations report
  14. Fermi GRB 260310A: Global MASTER-Net observations report
  15. GRB 260208A: radio detection with the VLA
  16. GRB 260307A: Glowbug gamma-ray detection
  17. Fermi GBM Sub-Threshold Detection of GRB 260307B
  18. GRB 260307B: Mephisto optical upper limits
  19. GRB 260307B: possible NOT optical counterpart
  20. GRB 260307B: SVOM/VT upper limit with X band data analysis
  21. Fermi GRB 260307A: Global MASTER-Net observations report
  22. GRB260307B: GROWTH-India Telescope optical upper limit
  23. GRB 260307B: SVOM/VT optical candidate
  24. GRB 260307B: SVOM/C-GFT upper limit
  25. GRB 260307B: SVOM detection of a burst
  26. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  27. GRB 260207A: TESS Detection and Possible VLA Counterpart
  28. EP260302a: SVOM/VT optical observation
  29. EP260306a: Gemini-North redshift z = 4.773
  30. EP260306a: SVOM/VT optical observation
  31. EP260302a: Gemini-South redshift z = 1.535
  32. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  33. EP260306a: Einstein Probe detection of an X-ray transient
  34. EP260302a: Optical afterglow rebrightening
  35. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  36. GRB 260303A: 1.3m DFOT optical upper limit
  37. Fermi GRB 260305A: Global MASTER-Net observations report
  38. GRB 260303B: AstroSat CZTI detection
  39. GRB 260303A: SVOM/VT optical observations
  40. GRB 260303A: J-band observations with WINTER
  41. GRB 260303B: NuSTAR detection of prompt emission
  42. EP260302a: Global MASTER-Net observations report
  43. Fermi GRB 260303B: Global MASTER-Net observations report
  44. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  45. EP260302a: analysis of the follow-up EP-FXT observation
  46. EP260302a: LCO observations
  47. EP260302a: BOOTES-7 optical counterpart detection at early times
  48. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  49. GRB 260303A: SVOM detection of a burst
  50. GRB 260228A: EP-FXT follow-up observation
  51. EP260302a: Einstein Probe detection of an X-ray transient
  52. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  53. GRB 251130B: TERI Gamma-ray detection
  54. GRB 260208A: TERI Gamma-ray detection
  55. EP260227a: Mondy optical observations
  56. GRB 260228A: CAHA 2.2m telescope optical upper limit
  57. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  58. EP260227a: Mephisto optical detection
  59. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  60. EP260227a: SVOM/VT optical observation
  61. GRB 260228A: SVOM/VT optical upper limits
  62. GRB 260225D: SVOM/GRM observation
  63. EP260227A: 3.6m DOT optical afterglow detection
  64. GRB 260225B: SVOM/GRM observation
  65. EP260227a: Liverpool Telescope optical observations
  66. EP260227a: LCOGT Optical Observations
  67. GRB 260226A: Asiago r-band upper limit
  68. EP260227a: Liverpool Telescope observations
  69. EP260227a: COLIBRÍ optical observations
  70. EP260227a: NOT optical observations
  71. EP260227a: Global MASTER-Net observations report
  72. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  73. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  74. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  75. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  76. EP260214a: VLT/FORS2 optical observations
  77. GRB 260225A: WINTER J-band upper limit
  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. LAT GRB260226.44: Global MASTER-Net observations report
  88. Fermi GRB 260226A: Global MASTER-Net observations report
  89. GRB 260226A: AstroSat CZTI detection of bright long burst
  90. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  91. EP260224a: LCO optical upper limits
  92. GRB 260225A: EP-FXT follow-up observation
  93. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  94. GRB 260223A: Fermi GBM Observation
  95. GRB 260225A: SVOM/VT optical upper limits
  96. EP260223a: Liverpool Telescope upper limits
  97. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  98. EP260224a: Einstein Probe detection of an X-ray transient
  99. EP 260225.148: COLIBRÍ Confirmation of flaring star
  100. EP260223a: Xinglong optical upper limit

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