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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: DDOTI Optical Candidate
  2. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  3. Fermi GRB 260223A: Global MASTER-Net observations report
  4. GRB 260223A: Fermi GBM Final Real-time Localization
  5. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  6. EP260221a: COLIBRÍ optical counterpart candidate
  7. EP260221a: Gemini South z-band upper limit
  8. GRB 260222A: Fermi GBM Final Real-time Localization
  9. EP260221a: Global MASTER-Net observations report
  10. EP260221a: EP-FXT follow-up observation
  11. Fermi GRB 260221B: Global MASTER-Net observations report
  12. GRB 260221B: Fermi GBM Final Real-time Localization
  13. EP-WXT01709258519: Xinglong optical upper limit
  14. EP260221a: Xinglong optical upper limit
  15. Fermi GRB 260221A: Global MASTER-Net observations report
  16. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  17. GRB 260221A: Fermi GBM Final Real-time Localization
  18. EP260221a: GOTO optical upper limit
  19. EP260221a: COLIBRÍ optical upper limit
  20. SVOM alert sb26021801: LCO optical upper limit
  21. EP260221a: Einstein Probe detection of an X-ray transient
  22. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  23. GRB 260219A: AstroSat CZTI detection
  24. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  25. GRB 260219A: GECAM-B observation of a long burst
  26. Fermi GRB 260219A: Global MASTER-Net observations report
  27. GRB 260219A: Fermi GBM Final Real-time Localization
  28. SVOM alert sb26021801: LAST optical upper limit
  29. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. IceCube Alert 260217A: Global MASTER-Net observations report
  31. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  32. GRB 260217A: Fermi GBM Final Localization
  33. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  34. sb26021801: SVOM detection of a long faint X-ray transient
  35. The EP-WXT trigger 01709258455 is likely a flaring star
  36. EP-WXT 01709258455: NOT optical upper limits
  37. EP260214b: Mondy optical observations
  38. EP260214b: 1.3m DFOT optical upper limit
  39. EP260210a: Mondy optical upper limits
  40. Konus-Wind detection of GRB 260212A
  41. GRB 260208A: AbAO and Terskol optical upper limits
  42. GRB 260208A: continued Mondy optical observations
  43. IPN triangulation of GRB 260212A
  44. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  45. GRB 260213A: GECAM-B observation of a short burst
  46. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  47. GRB 260216A: Fermi GBM Final Real-time Localization
  48. EP260214b: Liverpool Telescope optical observations
  49. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  50. EP260214b: Optical upper limit with Kinder observations
  51. EP260214a: Optical upper limits with Kinder observations
  52. EP260214b: EP-FXT follow-up observation
  53. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  54. EP260214b: DDOTI Optical Detection
  55. EP260214b: GROWTH-India Telescope optical upper limit
  56. EP260214a: VLT near-infrared observation
  57. EP260214b: SVOM/VT optical observation
  58. EP260214a: NOT optical upper limits
  59. EP260214a: COLIBRÍ optical upper limits
  60. EP260214b: OHP/T120 optical observations
  61. EP260214a: refined analysis of the EP-FXT observation
  62. EP260214b: LCO optical counterpart detection
  63. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  64. GRB 260211A: SVOM/VT optical counterpart
  65. EP260214b: COLIBRÍ optical observations
  66. EP260214a: SVOM/VT optical upper limits
  67. EP260214b: NOT optical counterpart detection
  68. EP260214b: Einstein Probe detection of a fast X-ray transient
  69. EP260214a: Global MASTER-Net observations report
  70. EP260214a: Einstein Probe detection of an X-ray transient
  71. GRB 260212A: AstroSat CZTI detection
  72. GRB 260212A: Fermi GBM Observation
  73. EP260213a: Liverpool Telescope optical upper limits
  74. EP260213a: Global MASTER-Net observations report
  75. EP260213a: COLIBRÍ optical upper limits
  76. GRB 260212A: GECAM-B observation
  77. EP260213a: Optical upper limits with Kinder observations
  78. EP260213a: SVOM/VT optical upper limit
  79. EP260213a: Mondy R-band optical upper limit
  80. EP260213a: NUTTelA-TAO Early Optical Limits
  81. EP260213a: SVOM/C-GFT upper limit
  82. EP260213a: refined analysis of the EP-FXT observation
  83. EP260213a: Einstein Probe detection of a fast X-ray transient
  84. EP/WXT 01709258378: NOT optical upper limits
  85. GRB 260212A: SVOM/GRM observation of a long burst
  86. GRB 260213B: Fermi GBM Final Localization
  87. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  88. GRB 260211A - SVOM/ECLAIRs refined analysis
  89. GRB 260204A: SVOM/ECLAIRs refined analysis
  90. GRB 260213A: Fermi GBM Final Localization
  91. GRB 260211A: EP-FXT follow-up observation
  92. GRB 260211A: SVOM/VT optical observation
  93. GRB 260212A: Glowbug gamma-ray detection
  94. GRB 260211A: GOTO optical upper limit
  95. Fermi GRB 260212A: Global MASTER-Net observations report
  96. GRB 260212A: Fermi GBM Final Real-time Localization
  97. GRB 260211A: LAST optical upper limit
  98. GRB 260210A: SVOM/GRM observation
  99. Fermi GBM Sub-Threshold Detection of GRB 260211A
  100. Konus-Wind detection of GRB 260207B

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