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

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