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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. EP260223a: EP-FXT follow-up observation
  2. sb26021801: SVOM/VT optical upper limits
  3. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  4. sb26021801: SVOM/C-GFT upper limit
  5. EP260223a: COLIBRÍ optical upper limits
  6. EP260223a: Einstein Probe detection of an X-ray transient
  7. GRB 260223A: SVOM/VT optical observation
  8. GRB 260223A: SVOM/GRM observation
  9. GRB 260223A: COLIBRÍ further optical observations and a brightening
  10. EP260221a: Optical upper limit with Kinder observations
  11. GRB 260223A: COLIBRÍ optical observations
  12. GRB 260223A: DDOTI Optical Candidate
  13. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  14. Fermi GRB 260223A: Global MASTER-Net observations report
  15. GRB 260223A: Fermi GBM Final Real-time Localization
  16. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  17. EP260221a: COLIBRÍ optical counterpart candidate
  18. EP260221a: Gemini South z-band upper limit
  19. GRB 260222A: Fermi GBM Final Real-time Localization
  20. EP260221a: Global MASTER-Net observations report
  21. EP260221a: EP-FXT follow-up observation
  22. Fermi GRB 260221B: Global MASTER-Net observations report
  23. GRB 260221B: Fermi GBM Final Real-time Localization
  24. EP-WXT01709258519: Xinglong optical upper limit
  25. EP260221a: Xinglong optical upper limit
  26. Fermi GRB 260221A: Global MASTER-Net observations report
  27. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  28. GRB 260221A: Fermi GBM Final Real-time Localization
  29. EP260221a: GOTO optical upper limit
  30. EP260221a: COLIBRÍ optical upper limit
  31. SVOM alert sb26021801: LCO optical upper limit
  32. EP260221a: Einstein Probe detection of an X-ray transient
  33. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  34. GRB 260219A: AstroSat CZTI detection
  35. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  36. GRB 260219A: GECAM-B observation of a long burst
  37. Fermi GRB 260219A: Global MASTER-Net observations report
  38. GRB 260219A: Fermi GBM Final Real-time Localization
  39. SVOM alert sb26021801: LAST optical upper limit
  40. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  41. IceCube Alert 260217A: Global MASTER-Net observations report
  42. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  43. GRB 260217A: Fermi GBM Final Localization
  44. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  45. sb26021801: SVOM detection of a long faint X-ray transient
  46. The EP-WXT trigger 01709258455 is likely a flaring star
  47. EP-WXT 01709258455: NOT optical upper limits
  48. EP260214b: Mondy optical observations
  49. EP260214b: 1.3m DFOT optical upper limit
  50. EP260210a: Mondy optical upper limits
  51. Konus-Wind detection of GRB 260212A
  52. GRB 260208A: AbAO and Terskol optical upper limits
  53. GRB 260208A: continued Mondy optical observations
  54. IPN triangulation of GRB 260212A
  55. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  56. GRB 260213A: GECAM-B observation of a short burst
  57. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  58. GRB 260216A: Fermi GBM Final Real-time Localization
  59. EP260214b: Liverpool Telescope optical observations
  60. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  61. EP260214b: Optical upper limit with Kinder observations
  62. EP260214a: Optical upper limits with Kinder observations
  63. EP260214b: EP-FXT follow-up observation
  64. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  65. EP260214b: DDOTI Optical Detection
  66. EP260214b: GROWTH-India Telescope optical upper limit
  67. EP260214a: VLT near-infrared observation
  68. EP260214b: SVOM/VT optical observation
  69. EP260214a: NOT optical upper limits
  70. EP260214a: COLIBRÍ optical upper limits
  71. EP260214b: OHP/T120 optical observations
  72. EP260214a: refined analysis of the EP-FXT observation
  73. EP260214b: LCO optical counterpart detection
  74. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  75. GRB 260211A: SVOM/VT optical counterpart
  76. EP260214b: COLIBRÍ optical observations
  77. EP260214a: SVOM/VT optical upper limits
  78. EP260214b: NOT optical counterpart detection
  79. EP260214b: Einstein Probe detection of a fast X-ray transient
  80. EP260214a: Global MASTER-Net observations report
  81. EP260214a: Einstein Probe detection of an X-ray transient
  82. GRB 260212A: AstroSat CZTI detection
  83. GRB 260212A: Fermi GBM Observation
  84. EP260213a: Liverpool Telescope optical upper limits
  85. EP260213a: Global MASTER-Net observations report
  86. EP260213a: COLIBRÍ optical upper limits
  87. GRB 260212A: GECAM-B observation
  88. EP260213a: Optical upper limits with Kinder observations
  89. EP260213a: SVOM/VT optical upper limit
  90. EP260213a: Mondy R-band optical upper limit
  91. EP260213a: NUTTelA-TAO Early Optical Limits
  92. EP260213a: SVOM/C-GFT upper limit
  93. EP260213a: refined analysis of the EP-FXT observation
  94. EP260213a: Einstein Probe detection of a fast X-ray transient
  95. EP/WXT 01709258378: NOT optical upper limits
  96. GRB 260212A: SVOM/GRM observation of a long burst
  97. GRB 260213B: Fermi GBM Final Localization
  98. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  99. GRB 260211A - SVOM/ECLAIRs refined analysis
  100. GRB 260204A: SVOM/ECLAIRs refined analysis

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