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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"

24365 results found.

  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 260225B: Fermi GBM Final Real-time Localization
  6. EP260126a: VLA 6 GHz detection
  7. GRB 260225A: SVOM detection of a burst
  8. EP260223a: Xinglong optical upper limit
  9. EP260213a: Mephisto optical upper limits
  10. sb26021801: SVOM/C-GFT upper limit
  11. GRB 260223A: SVOM/VT optical observation
  12. GRB 260223A: SVOM/GRM observation
  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. GRB 260222A: Fermi GBM Final Real-time Localization
  18. EP260221a: Global MASTER-Net observations report
  19. EP260221a: EP-FXT follow-up observation
  20. Fermi GRB 260221B: Global MASTER-Net observations report
  21. GRB 260221B: Fermi GBM Final Real-time Localization
  22. EP-WXT01709258519: Xinglong optical upper limit
  23. EP260221a: Xinglong optical upper limit
  24. Fermi GRB 260221A: Global MASTER-Net observations report
  25. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  26. GRB 260221A: Fermi GBM Final Real-time Localization
  27. EP260221a: GOTO optical upper limit
  28. SVOM alert sb26021801: LCO optical upper limit
  29. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  30. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 260219A: GECAM-B observation of a long burst
  32. Fermi GRB 260219A: Global MASTER-Net observations report
  33. GRB 260219A: Fermi GBM Final Real-time Localization
  34. IceCube Alert 260217A: Global MASTER-Net observations report
  35. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  36. GRB 260217A: Fermi GBM Final Localization
  37. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  38. sb26021801: SVOM detection of a long faint X-ray transient
  39. The EP-WXT trigger 01709258455 is likely a flaring star
  40. EP260214b: 1.3m DFOT optical upper limit
  41. Konus-Wind detection of GRB 260212A
  42. IPN triangulation of GRB 260212A
  43. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  44. GRB 260216A: Fermi GBM Final Real-time Localization
  45. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  46. EP260214a: Optical upper limits with Kinder observations
  47. EP260214b: EP-FXT follow-up observation
  48. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  49. EP260214b: DDOTI Optical Detection
  50. EP260214b: GROWTH-India Telescope optical upper limit
  51. EP260214b: SVOM/VT optical observation
  52. EP260214a: refined analysis of the EP-FXT observation
  53. EP260214a: SVOM/VT optical upper limits
  54. EP260214a: Global MASTER-Net observations report
  55. GRB 260212A: Fermi GBM Observation
  56. EP260213a: Global MASTER-Net observations report
  57. GRB 260212A: GECAM-B observation
  58. EP260213a: Optical upper limits with Kinder observations
  59. EP260213a: SVOM/VT optical upper limit
  60. EP260213a: NUTTelA-TAO Early Optical Limits
  61. EP260213a: SVOM/C-GFT upper limit
  62. EP260213a: refined analysis of the EP-FXT observation
  63. GRB 260212A: SVOM/GRM observation of a long burst
  64. GRB 260213B: Fermi GBM Final Localization
  65. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  66. GRB 260211A - SVOM/ECLAIRs refined analysis
  67. GRB 260204A: SVOM/ECLAIRs refined analysis
  68. GRB 260213A: Fermi GBM Final Localization
  69. GRB 260211A: EP-FXT follow-up observation
  70. GRB 260211A: SVOM/VT optical observation
  71. Fermi GRB 260212A: Global MASTER-Net observations report
  72. GRB 260212A: Fermi GBM Final Real-time Localization
  73. GRB 260210A: SVOM/GRM observation
  74. Fermi GBM Sub-Threshold Detection of GRB 260211A
  75. Konus-Wind detection of GRB 260207B
  76. GRB 260128B: SVOM/ECLAIRs refined analysis
  77. GRID detection of GRB 260207B
  78. GRB 260211A: LCO optical upper limits
  79. GRB260131A/B: 3.6m DOT Optical Observations
  80. Fermi trigger No 792537871: Global MASTER-Net observations report
  81. GRB 260211A: SVOM detection of a burst
  82. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  83. Konus-Wind detection of GRB 260209B
  84. Konus-Wind detection of GRB 260127B
  85. Fermi GRB 260210C: Global MASTER-Net observations report
  86. EP260210a: Global MASTER-Net observations report
  87. EP260210a: refined analysis of the EP-FXT observation
  88. EP260209a: Global MASTER-Net observations report
  89. EP260210a: Optical upper limits with Kinder observations
  90. IPN triangulation of GRB 260207B (short/hard with EE)
  91. GRB 260210C: Fermi GBM Final Real-time Localization
  92. GRB 260210B: Fermi GBM Final Real-time Localization
  93. EP260210a: SVOM/VT optical upper limit
  94. EP260210a: SVOM/C-GFT upper limit
  95. GRB 260208C: SVOM/GRM observation
  96. GRB260208A: Liverpool Telescope optical follow-up observations
  97. GRB 260208A: NuSTAR detection of prompt emission
  98. GRB 260208A: Fermi GBM Observation
  99. Fermi GRB 260209A: Global MASTER-Net observations report
  100. GRB 260208A: 1.3m DFOT optical detection

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