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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 250807A: Swift-BAT refined analysis
  2. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  3. GRB 250809A: Swift/UVOT Detection
  4. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  5. Corrected Swift-XRT Refined Analysis of GRB 250809A
  6. GRB 250809A: Swift-XRT refined Analysis
  7. GRB 250807B: SVOM/VT optical observation
  8. EP250807a: EP-FXT follow-up observation upper limit
  9. GRB 250809A: LCOGT Optical Upper Limits
  10. GRB 250702B: Chandra X-ray Detection
  11. EP250807a: Global MASTER-Net observations report
  12. Fermi GRB 250808A: Global MASTER-Net observations report
  13. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  14. GRB 250808A: VLT X-shooter candidate counterpart
  15. GRB 250809A: Prompt enhanced Swift-XRT position
  16. GRB 250809A: Swift detection of a gamma ray burst
  17. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. GRB 250808A: Fermi GBM Observation
  19. GRB 250808A: Swift-XRT candidate counterpart detection
  20. GRB 250807A: SVOM/VT optical continued observation
  21. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  22. GRB 250808A: SVOM detection of a long burst
  23. GRB 250808A: Fermi GBM Final Real-time Localization
  24. Konus-Wind detection of GRB 250807A
  25. GRB 250807B: Swift/UVOT Detection
  26. GRB 250807B: Kilonova-Catcher optical afterglow detection
  27. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  28. GRB 250807A: Swift/UVOT Detection
  29. GRB 250807A: Swift-XRT refined Analysis
  30. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  31. GRB 250806A: SVOM/MXT refined analysis
  32. GRB 250806A: SVOM/ECLAIRs refined analysis
  33. EP250807a: NTT z-band optical upper limit
  34. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  35. GRB 250804B: Insight-HXMT detection
  36. GRB 250807A: SVOM/GRM observation
  37. Swift GRB250807.45: Global MASTER-Net observations report
  38. GRB 250807A: AstroSat CZTI detection of bright long burst
  39. GRB 250807B: Swift-XRT refined Analysis
  40. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  41. GRB 250807B: NTT optical observations
  42. EP250807a: EP-WXT detection of a fast X-ray transient
  43. EP 250807.979: GOTO optical upper limit
  44. EP250807a: COLIBRÍ optical upper limit
  45. GRB 250807A: SVOM/VT optical observation
  46. EP250806a: Upper limit from Fermi-GBM Observations
  47. GRB 250807B: Enhanced Swift-XRT position
  48. Swift GRB250807.65: Global MASTER-Net observations report
  49. GRB 250807A: Enhanced Swift-XRT position
  50. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  51. GRB 250807B: Swift detection of a burst with an optical counterpart.
  52. GRB 250805A: Kilonova-Catcher optical upper limits
  53. EP250806a:SVOM/VT refined analysis
  54. GRB 250805A: Swift/UVOT Upper Limits
  55. GRB 250806A: Swift/UVOT U-band detection
  56. EP250806a: Liverpool telescope optical upper limit
  57. GRB 250807A: Swift detection of a burst with an optical counterpart
  58. IceCube Alert 250804.84: Global MASTER-Net observations report
  59. GRB 250806A: EP-FXT observation
  60. EP#01709198415/EP250806a: Swift-XRT observations
  61. EP250806a: Global MASTER-Net observations report
  62. EP250802a: EP-FXT follow-up observation
  63. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  64. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  65. EP250806a: SVOM /VT optical candidate
  66. GRB 250806A: J-band upper limit from WINTER
  67. GRB 250805A: Swift-BAT refined analysis
  68. GRB 250806A: KAIT optical upper limit
  69. GRB 250806A: SVOM/VT refined analysis
  70. GRB 250806A: Swift-XRT counterpart detection
  71. EP250806a: COLIBRÍ optical upper limit
  72. GRB 250806A: Kilonova-Catcher optical upper limits
  73. EP250806a: Einstein Probe detection of an X-ray transient
  74. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. GRB 250806A: SVOM/VT optical upper limit
  76. GRB 250806A: SVOM detection of a soft burst
  77. GRB 250805A: SVOM/VT optical counterpart
  78. GRB 250805A: ESO/VLT observations
  79. GRB 250805A: Swift-XRT refined Analysis
  80. GRB 250804B: Swift-XRT observations
  81. GRB 250805A: Enhanced Swift-XRT position
  82. GRB 250804C: AstroSat CZTI detection of a long burst
  83. GRB 250805A: TRT optical upper limits
  84. IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
  85. GRB 250805A: Swift-XRT observations
  86. GRB 250805A: Swift detection of a burst
  87. Swift GRB250805.26: Global MASTER-Net observations report
  88. GRB 250804B: Tiled Swift observations
  89. Fermi trigger No 776041355: Global MASTER-Net observations report
  90. GRB 250804B: SVOM/GRM observation of a short burst
  91. GRB 250804A: Fermi GBM Final Localization
  92. EP250802a: additional Liverpool Telescope upper limits
  93. EP250730a: SVOM/VT optical upper limit
  94. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  95. EP250802a: Liverpool Telescope optical upper limits
  96. EP250802a: Global MASTER-Net observations report
  97. EP250802a: GROWTH-India Telescope optical upper limit
  98. EP250802a: Einstein Probe detection of an X-ray transient
  99. LIGO/Virgo/KAGRA S250802dn: Updated Sky localization
  100. The EP-WXT trigger 01709198251 is likely a flaring star

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