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

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