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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. EP-WXT01709258519: Xinglong optical upper limit
  2. EP260221a: Xinglong optical upper limit
  3. Fermi GRB 260221A: Global MASTER-Net observations report
  4. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  5. GRB 260221A: Fermi GBM Final Real-time Localization
  6. EP260221a: GOTO optical upper limit
  7. EP260221a: COLIBRÍ optical upper limit
  8. SVOM alert sb26021801: LCO optical upper limit
  9. EP260221a: Einstein Probe detection of an X-ray transient
  10. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  11. GRB 260219A: AstroSat CZTI detection
  12. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  13. GRB 260219A: GECAM-B observation of a long burst
  14. Fermi GRB 260219A: Global MASTER-Net observations report
  15. GRB 260219A: Fermi GBM Final Real-time Localization
  16. SVOM alert sb26021801: LAST optical upper limit
  17. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. IceCube Alert 260217A: Global MASTER-Net observations report
  19. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  20. GRB 260217A: Fermi GBM Final Localization
  21. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  22. sb26021801: SVOM detection of a long faint X-ray transient
  23. The EP-WXT trigger 01709258455 is likely a flaring star
  24. EP-WXT 01709258455: NOT optical upper limits
  25. EP260214b: Mondy optical observations
  26. EP260214b: 1.3m DFOT optical upper limit
  27. EP260210a: Mondy optical upper limits
  28. Konus-Wind detection of GRB 260212A
  29. GRB 260208A: AbAO and Terskol optical upper limits
  30. GRB 260208A: continued Mondy optical observations
  31. IPN triangulation of GRB 260212A
  32. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  33. GRB 260213A: GECAM-B observation of a short burst
  34. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  35. GRB 260216A: Fermi GBM Final Real-time Localization
  36. EP260214b: Liverpool Telescope optical observations
  37. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  38. EP260214b: Optical upper limit with Kinder observations
  39. EP260214a: Optical upper limits with Kinder observations
  40. EP260214b: EP-FXT follow-up observation
  41. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  42. EP260214b: DDOTI Optical Detection
  43. EP260214b: GROWTH-India Telescope optical upper limit
  44. EP260214a: VLT near-infrared observation
  45. EP260214b: SVOM/VT optical observation
  46. EP260214a: NOT optical upper limits
  47. EP260214a: COLIBRÍ optical upper limits
  48. EP260214b: OHP/T120 optical observations
  49. EP260214a: refined analysis of the EP-FXT observation
  50. EP260214b: LCO optical counterpart detection
  51. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  52. GRB 260211A: SVOM/VT optical counterpart
  53. EP260214b: COLIBRÍ optical observations
  54. EP260214a: SVOM/VT optical upper limits
  55. EP260214b: NOT optical counterpart detection
  56. EP260214b: Einstein Probe detection of a fast X-ray transient
  57. EP260214a: Global MASTER-Net observations report
  58. EP260214a: Einstein Probe detection of an X-ray transient
  59. GRB 260212A: AstroSat CZTI detection
  60. GRB 260212A: Fermi GBM Observation
  61. EP260213a: Liverpool Telescope optical upper limits
  62. EP260213a: Global MASTER-Net observations report
  63. EP260213a: COLIBRÍ optical upper limits
  64. GRB 260212A: GECAM-B observation
  65. EP260213a: Optical upper limits with Kinder observations
  66. EP260213a: SVOM/VT optical upper limit
  67. EP260213a: Mondy R-band optical upper limit
  68. EP260213a: NUTTelA-TAO Early Optical Limits
  69. EP260213a: SVOM/C-GFT upper limit
  70. EP260213a: refined analysis of the EP-FXT observation
  71. EP260213a: Einstein Probe detection of a fast X-ray transient
  72. EP/WXT 01709258378: NOT optical upper limits
  73. GRB 260212A: SVOM/GRM observation of a long burst
  74. GRB 260213B: Fermi GBM Final Localization
  75. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  76. GRB 260211A - SVOM/ECLAIRs refined analysis
  77. GRB 260204A: SVOM/ECLAIRs refined analysis
  78. GRB 260213A: Fermi GBM Final Localization
  79. GRB 260211A: EP-FXT follow-up observation
  80. GRB 260211A: SVOM/VT optical observation
  81. GRB 260212A: Glowbug gamma-ray detection
  82. GRB 260211A: GOTO optical upper limit
  83. Fermi GRB 260212A: Global MASTER-Net observations report
  84. GRB 260212A: Fermi GBM Final Real-time Localization
  85. GRB 260211A: LAST optical upper limit
  86. GRB 260210A: SVOM/GRM observation
  87. Fermi GBM Sub-Threshold Detection of GRB 260211A
  88. Konus-Wind detection of GRB 260207B
  89. GRB 260128B: SVOM/ECLAIRs refined analysis
  90. GRID detection of GRB 260207B
  91. GRB 260211A: LCO optical upper limits
  92. GRB260131A/B: 3.6m DOT Optical Observations
  93. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  94. Fermi trigger No 792537871: Global MASTER-Net observations report
  95. GRB 260211A: SVOM detection of a burst
  96. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  97. Konus-Wind detection of GRB 260209B
  98. GRB 260208A: Swift UVOT detection
  99. Konus-Wind detection of GRB 260127B
  100. EP260209a: COLIBRÍ optical upper limit

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