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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"

24356 results found.

  1. GRB 260313A: A Correction to the Fermi GBM Final Localization
  2. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  3. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  4. GRB 260313A: Fermi GBM Final Real-time Localization
  5. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  6. GRB260310A / AT2026fgk: P200 Spectroscopy
  7. GRB 260310A: Fermi GBM Observation
  8. GRB 260310A: potential optical counterpart
  9. Fermi GRB 260312B: Global MASTER-Net observations report
  10. Fermi GRB 260311B: Global MASTER-Net observations report
  11. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  12. GRB 260312B: Fermi GBM Final Real-time Localization
  13. The EP-WXT trigger 01709258843 is not a real source
  14. GRB 260311B: Fermi GBM Final Real-time Localization
  15. EP260302a: MeerKAT radio counterpart
  16. GRB 260308A: SVOM/GRM observation of a short GRB
  17. GRB 260311A: Fermi GBM Final Real-time Localization
  18. Fermi GRB 260310B: Global MASTER-Net observations report
  19. GRB 260310B: Fermi GBM Final Real-time Localization
  20. Fermi GRB 260310A: Global MASTER-Net observations report
  21. GRB 260307B: SVOM/ECLAIRs refined analysis
  22. GRB 260310A: Fermi GBM Final Real-time Localization
  23. GRB 260308A: Fermi GBM Final Real-time Localization
  24. Fermi GBM Sub-Threshold Detection of GRB 260307B
  25. GRB 260307B: Mephisto optical upper limits
  26. GRB 260307B: possible NOT optical counterpart
  27. GRB 260307B: SVOM/VT upper limit with X band data analysis
  28. Fermi GRB 260307A: Global MASTER-Net observations report
  29. GRB260307B: GROWTH-India Telescope optical upper limit
  30. GRB 260307B: SVOM/VT optical candidate
  31. GRB 260307B: SVOM/C-GFT upper limit
  32. GRB 260307B: SVOM detection of a burst
  33. GRB 260307A: Fermi GBM Final Localization
  34. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  35. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  36. GRB 260207A: TESS Detection and Possible VLA Counterpart
  37. EP260302a: SVOM/VT optical observation
  38. EP260306a: Gemini-North redshift z = 4.773
  39. EP260306a: SVOM/VT optical observation
  40. EP260302a: Gemini-South redshift z = 1.535
  41. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  42. GRB 260303A: 1.3m DFOT optical upper limit
  43. GRB 260303A: SVOM/ECLAIRs refined analysis
  44. Fermi GRB 260305A: Global MASTER-Net observations report
  45. GRB 260305A: Fermi GBM Final Real-time Localization
  46. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  47. GRB 260303A: SVOM/VT optical observations
  48. GRB 260303B: NuSTAR detection of prompt emission
  49. EP260302a: Global MASTER-Net observations report
  50. Fermi GRB 260303B: Global MASTER-Net observations report
  51. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  52. GRB 260228A: SVOM/ECLAIRs refined analysis
  53. GRB 260225A: SVOM/ECLAIRs refined analysis
  54. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  55. GRB 260303B: Fermi GBM Final Real-time Localization
  56. EP260302a: BOOTES-7 optical counterpart detection at early times
  57. GRB 260303A: SVOM detection of a burst
  58. GRB 260228A: EP-FXT follow-up observation
  59. GRB 260302A: Fermi GBM Final Real-time Localization
  60. EP260227a: Mephisto optical detection
  61. EP260227a: SVOM/VT optical observation
  62. GRB 260228A: SVOM/VT optical upper limits
  63. GRB 260225D: SVOM/GRM observation
  64. EP260227A: 3.6m DOT optical afterglow detection
  65. GRB 260225B: SVOM/GRM observation
  66. GRB 260228A: SVOM detection of a burst
  67. EP260227a: LCOGT Optical Observations
  68. GRB 260226A: Asiago r-band upper limit
  69. EP260227a: Thai National Telescope observations
  70. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  71. GRB 260225A: SVOM/VT optical continued observations and upper limit
  72. EP260227a: Global MASTER-Net observations report
  73. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  74. IceCube cascade alert 142200_1517143 retraction
  75. Konus-Wind detection of GRB 260226A
  76. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  77. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  78. GRB 260226A: LCOGT Optical Upper Limit
  79. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  80. GRB 260226A: Glowbug gamma-ray detection
  81. GRB 260226A: NuSTAR detection of bright prompt emission
  82. GRB 260226A : GROWTH-India Telescope optical observations
  83. GRB 260226A: Fermi GBM observation
  84. GRB 260226A: Fermi-LAT refined analysis
  85. The EP-WXT trigger 01709258652 is likely a flaring star
  86. LAT GRB260226.44: Global MASTER-Net observations report
  87. Fermi GRB 260226A: Global MASTER-Net observations report
  88. GRB 260226A: Fermi-LAT detection of a bright burst
  89. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  90. GRB 260226A: Fermi GBM Final Real-time Localization
  91. GRB 260225A: EP-FXT follow-up observation
  92. GRB 260225A: SVOM/VT optical observation
  93. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  94. GRB 260225C: Fermi GBM Final Real-time Localization
  95. GRB 260223A: Fermi GBM Observation
  96. GRB 260225B: Fermi GBM Final Real-time Localization
  97. EP260126a: VLA 6 GHz detection
  98. GRB 260225A: SVOM detection of a burst
  99. EP260223a: Xinglong optical upper limit
  100. EP260213a: Mephisto optical upper limits

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