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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 260223A: Glowbug gamma-ray detection
  2. EP260213a: Mephisto optical upper limits
  3. EP260223a: EP-FXT follow-up observation
  4. sb26021801: SVOM/VT optical upper limits
  5. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  6. sb26021801: SVOM/C-GFT upper limit
  7. EP260223a: COLIBRÍ optical upper limits
  8. EP260223a: Einstein Probe detection of an X-ray transient
  9. GRB 260223A: SVOM/VT optical observation
  10. GRB 260223A: SVOM/GRM observation
  11. GRB 260223A: COLIBRÍ further optical observations and a brightening
  12. EP260221a: Optical upper limit with Kinder observations
  13. GRB 260223A: COLIBRÍ optical observations
  14. GRB 260223A: DDOTI Optical Candidate
  15. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  16. Fermi GRB 260223A: Global MASTER-Net observations report
  17. GRB 260223A: Fermi GBM Final Real-time Localization
  18. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  19. EP260221a: COLIBRÍ optical counterpart candidate
  20. EP260221a: Gemini South z-band upper limit
  21. GRB 260222A: Fermi GBM Final Real-time Localization
  22. EP260221a: Global MASTER-Net observations report
  23. EP260221a: EP-FXT follow-up observation
  24. Fermi GRB 260221B: Global MASTER-Net observations report
  25. GRB 260221B: Fermi GBM Final Real-time Localization
  26. EP-WXT01709258519: Xinglong optical upper limit
  27. EP260221a: Xinglong optical upper limit
  28. Fermi GRB 260221A: Global MASTER-Net observations report
  29. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  30. GRB 260221A: Fermi GBM Final Real-time Localization
  31. EP260221a: GOTO optical upper limit
  32. EP260221a: COLIBRÍ optical upper limit
  33. SVOM alert sb26021801: LCO optical upper limit
  34. EP260221a: Einstein Probe detection of an X-ray transient
  35. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  36. GRB 260219A: AstroSat CZTI detection
  37. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  38. GRB 260219A: GECAM-B observation of a long burst
  39. Fermi GRB 260219A: Global MASTER-Net observations report
  40. GRB 260219A: Fermi GBM Final Real-time Localization
  41. SVOM alert sb26021801: LAST optical upper limit
  42. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. IceCube Alert 260217A: Global MASTER-Net observations report
  44. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  45. GRB 260217A: Fermi GBM Final Localization
  46. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  47. sb26021801: SVOM detection of a long faint X-ray transient
  48. The EP-WXT trigger 01709258455 is likely a flaring star
  49. EP-WXT 01709258455: NOT optical upper limits
  50. EP260214b: Mondy optical observations
  51. EP260214b: 1.3m DFOT optical upper limit
  52. EP260210a: Mondy optical upper limits
  53. Konus-Wind detection of GRB 260212A
  54. GRB 260208A: AbAO and Terskol optical upper limits
  55. GRB 260208A: continued Mondy optical observations
  56. IPN triangulation of GRB 260212A
  57. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 260213A: GECAM-B observation of a short burst
  59. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  60. GRB 260216A: Fermi GBM Final Real-time Localization
  61. EP260214b: Liverpool Telescope optical observations
  62. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  63. EP260214b: Optical upper limit with Kinder observations
  64. EP260214a: Optical upper limits with Kinder observations
  65. EP260214b: EP-FXT follow-up observation
  66. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  67. EP260214b: DDOTI Optical Detection
  68. EP260214b: GROWTH-India Telescope optical upper limit
  69. EP260214a: VLT near-infrared observation
  70. EP260214b: SVOM/VT optical observation
  71. EP260214a: NOT optical upper limits
  72. EP260214a: COLIBRÍ optical upper limits
  73. EP260214b: OHP/T120 optical observations
  74. EP260214a: refined analysis of the EP-FXT observation
  75. EP260214b: LCO optical counterpart detection
  76. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  77. GRB 260211A: SVOM/VT optical counterpart
  78. EP260214b: COLIBRÍ optical observations
  79. EP260214a: SVOM/VT optical upper limits
  80. EP260214b: NOT optical counterpart detection
  81. EP260214b: Einstein Probe detection of a fast X-ray transient
  82. EP260214a: Global MASTER-Net observations report
  83. EP260214a: Einstein Probe detection of an X-ray transient
  84. GRB 260212A: AstroSat CZTI detection
  85. GRB 260212A: Fermi GBM Observation
  86. EP260213a: Liverpool Telescope optical upper limits
  87. EP260213a: Global MASTER-Net observations report
  88. EP260213a: COLIBRÍ optical upper limits
  89. GRB 260212A: GECAM-B observation
  90. EP260213a: Optical upper limits with Kinder observations
  91. EP260213a: SVOM/VT optical upper limit
  92. EP260213a: Mondy R-band optical upper limit
  93. EP260213a: NUTTelA-TAO Early Optical Limits
  94. EP260213a: SVOM/C-GFT upper limit
  95. EP260213a: refined analysis of the EP-FXT observation
  96. EP260213a: Einstein Probe detection of a fast X-ray transient
  97. EP/WXT 01709258378: NOT optical upper limits
  98. GRB 260212A: SVOM/GRM observation of a long burst
  99. GRB 260213B: Fermi GBM Final Localization
  100. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)

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