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

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