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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"

24171 results found.

  1. LAT GRB260226.44: Global MASTER-Net observations report
  2. Fermi GRB 260226A: Global MASTER-Net observations report
  3. GRB 260226A: Fermi-LAT detection of a bright burst
  4. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  5. GRB 260226A: Fermi GBM Final Real-time Localization
  6. GRB 260225A: EP-FXT follow-up observation
  7. GRB 260225A: SVOM/VT optical observation
  8. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  9. GRB 260225C: Fermi GBM Final Real-time Localization
  10. GRB 260223A: Fermi GBM Observation
  11. GRB 260225B: Fermi GBM Final Real-time Localization
  12. EP260126a: VLA 6 GHz detection
  13. GRB 260225A: SVOM detection of a burst
  14. EP260223a: Xinglong optical upper limit
  15. EP260213a: Mephisto optical upper limits
  16. sb26021801: SVOM/C-GFT upper limit
  17. GRB 260223A: SVOM/VT optical observation
  18. GRB 260223A: SVOM/GRM observation
  19. GRB 260223A: DDOTI Optical Candidate
  20. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  21. Fermi GRB 260223A: Global MASTER-Net observations report
  22. GRB 260223A: Fermi GBM Final Real-time Localization
  23. GRB 260222A: Fermi GBM Final Real-time Localization
  24. EP260221a: Global MASTER-Net observations report
  25. EP260221a: EP-FXT follow-up observation
  26. Fermi GRB 260221B: Global MASTER-Net observations report
  27. GRB 260221B: Fermi GBM Final Real-time Localization
  28. EP-WXT01709258519: Xinglong optical upper limit
  29. EP260221a: Xinglong optical upper limit
  30. Fermi GRB 260221A: Global MASTER-Net observations report
  31. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  32. GRB 260221A: Fermi GBM Final Real-time Localization
  33. EP260221a: GOTO optical upper limit
  34. SVOM alert sb26021801: LCO optical upper limit
  35. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  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. IceCube Alert 260217A: Global MASTER-Net observations report
  41. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  42. GRB 260217A: Fermi GBM Final Localization
  43. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  44. sb26021801: SVOM detection of a long faint X-ray transient
  45. The EP-WXT trigger 01709258455 is likely a flaring star
  46. EP260214b: 1.3m DFOT optical upper limit
  47. Konus-Wind detection of GRB 260212A
  48. IPN triangulation of GRB 260212A
  49. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 260216A: Fermi GBM Final Real-time Localization
  51. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  52. EP260214a: Optical upper limits with Kinder observations
  53. EP260214b: EP-FXT follow-up observation
  54. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  55. EP260214b: DDOTI Optical Detection
  56. EP260214b: GROWTH-India Telescope optical upper limit
  57. EP260214b: SVOM/VT optical observation
  58. EP260214a: refined analysis of the EP-FXT observation
  59. EP260214a: SVOM/VT optical upper limits
  60. EP260214a: Global MASTER-Net observations report
  61. GRB 260212A: Fermi GBM Observation
  62. EP260213a: Global MASTER-Net observations report
  63. GRB 260212A: GECAM-B observation
  64. EP260213a: Optical upper limits with Kinder observations
  65. EP260213a: SVOM/VT optical upper limit
  66. EP260213a: NUTTelA-TAO Early Optical Limits
  67. EP260213a: SVOM/C-GFT upper limit
  68. EP260213a: refined analysis of the EP-FXT observation
  69. GRB 260212A: SVOM/GRM observation of a long burst
  70. GRB 260213B: Fermi GBM Final Localization
  71. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  72. GRB 260211A - SVOM/ECLAIRs refined analysis
  73. GRB 260204A: SVOM/ECLAIRs refined analysis
  74. GRB 260213A: Fermi GBM Final Localization
  75. GRB 260211A: EP-FXT follow-up observation
  76. GRB 260211A: SVOM/VT optical observation
  77. Fermi GRB 260212A: Global MASTER-Net observations report
  78. GRB 260212A: Fermi GBM Final Real-time Localization
  79. GRB 260210A: SVOM/GRM observation
  80. Fermi GBM Sub-Threshold Detection of GRB 260211A
  81. Konus-Wind detection of GRB 260207B
  82. GRB 260128B: SVOM/ECLAIRs refined analysis
  83. GRID detection of GRB 260207B
  84. GRB 260211A: LCO optical upper limits
  85. GRB260131A/B: 3.6m DOT Optical Observations
  86. Fermi trigger No 792537871: Global MASTER-Net observations report
  87. GRB 260211A: SVOM detection of a burst
  88. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  89. Konus-Wind detection of GRB 260209B
  90. Konus-Wind detection of GRB 260127B
  91. Fermi GRB 260210C: Global MASTER-Net observations report
  92. EP260210a: Global MASTER-Net observations report
  93. EP260210a: refined analysis of the EP-FXT observation
  94. EP260209a: Global MASTER-Net observations report
  95. EP260210a: Optical upper limits with Kinder observations
  96. IPN triangulation of GRB 260207B (short/hard with EE)
  97. GRB 260210C: Fermi GBM Final Real-time Localization
  98. GRB 260210B: Fermi GBM Final Real-time Localization
  99. EP260210a: SVOM/VT optical upper limit
  100. EP260210a: SVOM/C-GFT upper limit

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