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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"

28085 results found.

  1. GRB 260303A: SVOM detection of a burst
  2. GRB 260228A: EP-FXT follow-up observation
  3. EP260302a: Einstein Probe detection of an X-ray transient
  4. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  5. GRB 251130B: TERI Gamma-ray detection
  6. GRB 260208A: TERI Gamma-ray detection
  7. EP260227a: Mondy optical observations
  8. GRB 260228A: CAHA 2.2m telescope optical upper limit
  9. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  10. EP260227a: Mephisto optical detection
  11. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  12. EP260227a: SVOM/VT optical observation
  13. GRB 260228A: SVOM/VT optical upper limits
  14. GRB 260225D: SVOM/GRM observation
  15. EP260227A: 3.6m DOT optical afterglow detection
  16. GRB 260225B: SVOM/GRM observation
  17. EP260227a: Liverpool Telescope optical observations
  18. EP260227a: LCOGT Optical Observations
  19. GRB 260226A: Asiago r-band upper limit
  20. EP260227a: Liverpool Telescope observations
  21. EP260227a: COLIBRÍ optical observations
  22. EP260227a: NOT optical observations
  23. EP260227a: Global MASTER-Net observations report
  24. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  25. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  26. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  27. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  28. EP260214a: VLT/FORS2 optical observations
  29. GRB 260225A: WINTER J-band upper limit
  30. GRB 260226A: COLIBRÍ optical upper limits
  31. GRB 260226A: LCOGT Optical Upper Limit
  32. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  33. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  34. GRB 260226A: Glowbug gamma-ray detection
  35. GRB 260226A: NuSTAR detection of bright prompt emission
  36. GRB 260226A : GROWTH-India Telescope optical observations
  37. GRB 260226A: LAST optical upper limit
  38. GRB 260226A: Fermi GBM observation
  39. LAT GRB260226.44: Global MASTER-Net observations report
  40. Fermi GRB 260226A: Global MASTER-Net observations report
  41. GRB 260226A: AstroSat CZTI detection of bright long burst
  42. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  43. EP260224a: LCO optical upper limits
  44. GRB 260225A: EP-FXT follow-up observation
  45. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  46. GRB 260223A: Fermi GBM Observation
  47. GRB 260225A: SVOM/VT optical upper limits
  48. EP260223a: Liverpool Telescope upper limits
  49. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  50. EP260224a: Einstein Probe detection of an X-ray transient
  51. EP 260225.148: COLIBRÍ Confirmation of flaring star
  52. EP260223a: Xinglong optical upper limit
  53. GRB 260223A: Glowbug gamma-ray detection
  54. EP260213a: Mephisto optical upper limits
  55. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  56. sb26021801: SVOM/C-GFT upper limit
  57. EP260223a: COLIBRÍ optical upper limits
  58. EP260223a: Einstein Probe detection of an X-ray transient
  59. GRB 260223A: SVOM/GRM observation
  60. GRB 260223A: COLIBRÍ further optical observations and a brightening
  61. EP260221a: Optical upper limit with Kinder observations
  62. GRB 260223A: COLIBRÍ optical observations
  63. GRB 260223A: DDOTI Optical Candidate
  64. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  65. Fermi GRB 260223A: Global MASTER-Net observations report
  66. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  67. EP260221a: COLIBRÍ optical counterpart candidate
  68. EP260221a: Gemini South z-band upper limit
  69. EP260221a: Global MASTER-Net observations report
  70. EP260221a: EP-FXT follow-up observation
  71. Fermi GRB 260221B: Global MASTER-Net observations report
  72. EP-WXT01709258519: Xinglong optical upper limit
  73. EP260221a: Xinglong optical upper limit
  74. Fermi GRB 260221A: Global MASTER-Net observations report
  75. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  76. EP260221a: GOTO optical upper limit
  77. EP260221a: COLIBRÍ optical upper limit
  78. SVOM alert sb26021801: LCO optical upper limit
  79. EP260221a: Einstein Probe detection of an X-ray transient
  80. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  81. Fermi GRB 260219A: Global MASTER-Net observations report
  82. SVOM alert sb26021801: LAST optical upper limit
  83. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. IceCube Alert 260217A: Global MASTER-Net observations report
  85. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  86. sb26021801: SVOM detection of a long faint X-ray transient
  87. EP-WXT 01709258455: NOT optical upper limits
  88. EP260214b: Mondy optical observations
  89. EP260214b: 1.3m DFOT optical upper limit
  90. EP260210a: Mondy optical upper limits
  91. GRB 260208A: AbAO and Terskol optical upper limits
  92. GRB 260208A: continued Mondy optical observations
  93. IPN triangulation of GRB 260212A
  94. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  95. EP260214b: Liverpool Telescope optical observations
  96. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  97. EP260214b: Optical upper limit with Kinder observations
  98. EP260214a: Optical upper limits with Kinder observations
  99. EP260214b: EP-FXT follow-up observation
  100. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection

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