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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 260225C: Fermi GBM Final Real-time Localization
  2. GRB 260223A: Fermi GBM Observation
  3. GRB 260225A: SVOM/VT optical upper limits
  4. GRB 260225B: Fermi GBM Final Real-time Localization
  5. EP260126a: VLA 6 GHz detection
  6. EP260223a: Liverpool Telescope upper limits
  7. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  8. GRB 260225A: SVOM detection of a burst
  9. EP260224a: Einstein Probe detection of an X-ray transient
  10. EP 260225.148: COLIBRÍ Confirmation of flaring star
  11. EP260223a: Xinglong optical upper limit
  12. The EP-WXT trigger 01709258631 is likely a flaring star
  13. GRB 260223A: Glowbug gamma-ray detection
  14. EP260213a: Mephisto optical upper limits
  15. EP260223a: EP-FXT follow-up observation
  16. sb26021801: SVOM/VT optical upper limits
  17. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  18. sb26021801: SVOM/C-GFT upper limit
  19. EP260223a: COLIBRÍ optical upper limits
  20. EP260223a: Einstein Probe detection of an X-ray transient
  21. GRB 260223A: SVOM/VT optical observation
  22. GRB 260223A: SVOM/GRM observation
  23. GRB 260223A: COLIBRÍ further optical observations and a brightening
  24. EP260221a: Optical upper limit with Kinder observations
  25. GRB 260223A: COLIBRÍ optical observations
  26. GRB 260223A: DDOTI Optical Candidate
  27. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  28. Fermi GRB 260223A: Global MASTER-Net observations report
  29. GRB 260223A: Fermi GBM Final Real-time Localization
  30. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  31. EP260221a: COLIBRÍ optical counterpart candidate
  32. EP260221a: Gemini South z-band upper limit
  33. GRB 260222A: Fermi GBM Final Real-time Localization
  34. EP260221a: Global MASTER-Net observations report
  35. EP260221a: EP-FXT follow-up observation
  36. Fermi GRB 260221B: Global MASTER-Net observations report
  37. GRB 260221B: Fermi GBM Final Real-time Localization
  38. EP-WXT01709258519: Xinglong optical upper limit
  39. EP260221a: Xinglong optical upper limit
  40. Fermi GRB 260221A: Global MASTER-Net observations report
  41. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  42. GRB 260221A: Fermi GBM Final Real-time Localization
  43. EP260221a: GOTO optical upper limit
  44. EP260221a: COLIBRÍ optical upper limit
  45. SVOM alert sb26021801: LCO optical upper limit
  46. EP260221a: Einstein Probe detection of an X-ray transient
  47. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  48. GRB 260219A: AstroSat CZTI detection
  49. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  50. GRB 260219A: GECAM-B observation of a long burst
  51. Fermi GRB 260219A: Global MASTER-Net observations report
  52. GRB 260219A: Fermi GBM Final Real-time Localization
  53. SVOM alert sb26021801: LAST optical upper limit
  54. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  55. IceCube Alert 260217A: Global MASTER-Net observations report
  56. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  57. GRB 260217A: Fermi GBM Final Localization
  58. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  59. sb26021801: SVOM detection of a long faint X-ray transient
  60. The EP-WXT trigger 01709258455 is likely a flaring star
  61. EP-WXT 01709258455: NOT optical upper limits
  62. EP260214b: Mondy optical observations
  63. EP260214b: 1.3m DFOT optical upper limit
  64. EP260210a: Mondy optical upper limits
  65. Konus-Wind detection of GRB 260212A
  66. GRB 260208A: AbAO and Terskol optical upper limits
  67. GRB 260208A: continued Mondy optical observations
  68. IPN triangulation of GRB 260212A
  69. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  70. GRB 260213A: GECAM-B observation of a short burst
  71. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  72. GRB 260216A: Fermi GBM Final Real-time Localization
  73. EP260214b: Liverpool Telescope optical observations
  74. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  75. EP260214b: Optical upper limit with Kinder observations
  76. EP260214a: Optical upper limits with Kinder observations
  77. EP260214b: EP-FXT follow-up observation
  78. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  79. EP260214b: DDOTI Optical Detection
  80. EP260214b: GROWTH-India Telescope optical upper limit
  81. EP260214a: VLT near-infrared observation
  82. EP260214b: SVOM/VT optical observation
  83. EP260214a: NOT optical upper limits
  84. EP260214a: COLIBRÍ optical upper limits
  85. EP260214b: OHP/T120 optical observations
  86. EP260214a: refined analysis of the EP-FXT observation
  87. EP260214b: LCO optical counterpart detection
  88. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  89. GRB 260211A: SVOM/VT optical counterpart
  90. EP260214b: COLIBRÍ optical observations
  91. EP260214a: SVOM/VT optical upper limits
  92. EP260214b: NOT optical counterpart detection
  93. EP260214b: Einstein Probe detection of a fast X-ray transient
  94. EP260214a: Global MASTER-Net observations report
  95. EP260214a: Einstein Probe detection of an X-ray transient
  96. GRB 260212A: AstroSat CZTI detection
  97. GRB 260212A: Fermi GBM Observation
  98. EP260213a: Liverpool Telescope optical upper limits
  99. EP260213a: Global MASTER-Net observations report
  100. EP260213a: COLIBRÍ optical upper limits

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