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

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