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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. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  2. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  3. EP250812a: Nickel optical upper limit
  4. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  5. GRB 250812A: NTT spectroscopic redshift z = 2.57
  6. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  7. EP250812a: NOT, NTT, and GS observations
  8. GRB 250812A: Swift/UVOT Detection
  9. GRB 250813A: Fermi GBM Final Localization
  10. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  11. EP250812a: Liverpool Telescope upper limits
  12. EP250812a: SVOM/VT optical counterpart
  13. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  14. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  15. IceCube Alert 250813.14: Global MASTER-Net observations report
  16. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  17. GRB 250812A: EP-FXT counterpart detection
  18. GRB 250812A: Swift ToO observations
  19. GRB 250807B: Swift-BAT refined analysis
  20. EP 250812a: GOTO optical upper limit
  21. GRB 250812A: Kilonova-Catcher optical afterglow detection
  22. EP250812a: Swift-XRT counterpart detection
  23. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  24. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  25. EP250812a: Einstein Probe detection of an X-ray transient
  26. GRB 250812A: SVOM/VT optical afterglow confirmation
  27. GRB 250812A: Swift-XRT afterglow detection
  28. GRB 250812A: TRT likely optical counterpart detection
  29. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 250812A: SVOM detection of a faint long burst
  31. GRB 250809A: Swift-BAT refined analysis
  32. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  33. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  34. GRB 250807A: Swift-BAT refined analysis
  35. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  36. GRB 250809A: Swift/UVOT Detection
  37. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  38. Corrected Swift-XRT Refined Analysis of GRB 250809A
  39. GRB 250809A: Swift-XRT refined Analysis
  40. GRB 250807B: SVOM/VT optical observation
  41. EP250807a: EP-FXT follow-up observation upper limit
  42. GRB 250809A: LCOGT Optical Upper Limits
  43. GRB 250702B: Chandra X-ray Detection
  44. EP250807a: Global MASTER-Net observations report
  45. Fermi GRB 250808A: Global MASTER-Net observations report
  46. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  47. GRB 250808A: VLT X-shooter candidate counterpart
  48. GRB 250809A: Prompt enhanced Swift-XRT position
  49. GRB 250809A: Swift detection of a gamma ray burst
  50. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. GRB 250808A: Fermi GBM Observation
  52. GRB 250808A: Swift-XRT candidate counterpart detection
  53. GRB 250807A: SVOM/VT optical continued observation
  54. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  55. GRB 250808A: SVOM detection of a long burst
  56. GRB 250808A: Fermi GBM Final Real-time Localization
  57. Konus-Wind detection of GRB 250807A
  58. GRB 250807B: Swift/UVOT Detection
  59. GRB 250807B: Kilonova-Catcher optical afterglow detection
  60. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 250807A: Swift/UVOT Detection
  62. GRB 250807A: Swift-XRT refined Analysis
  63. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  64. GRB 250806A: SVOM/MXT refined analysis
  65. GRB 250806A: SVOM/ECLAIRs refined analysis
  66. EP250807a: NTT z-band optical upper limit
  67. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  68. GRB 250804B: Insight-HXMT detection
  69. GRB 250807A: SVOM/GRM observation
  70. Swift GRB250807.45: Global MASTER-Net observations report
  71. GRB 250807A: AstroSat CZTI detection of bright long burst
  72. GRB 250807B: Swift-XRT refined Analysis
  73. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  74. GRB 250807B: NTT optical observations
  75. EP250807a: EP-WXT detection of a fast X-ray transient
  76. EP 250807.979: GOTO optical upper limit
  77. EP250807a: COLIBRÍ optical upper limit
  78. GRB 250807A: SVOM/VT optical observation
  79. EP250806a: Upper limit from Fermi-GBM Observations
  80. GRB 250807B: Enhanced Swift-XRT position
  81. Swift GRB250807.65: Global MASTER-Net observations report
  82. GRB 250807A: Enhanced Swift-XRT position
  83. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  84. GRB 250807B: Swift detection of a burst with an optical counterpart.
  85. GRB 250805A: Kilonova-Catcher optical upper limits
  86. EP250806a:SVOM/VT refined analysis
  87. GRB 250805A: Swift/UVOT Upper Limits
  88. GRB 250806A: Swift/UVOT U-band detection
  89. EP250806a: Liverpool telescope optical upper limit
  90. GRB 250807A: Swift detection of a burst with an optical counterpart
  91. IceCube Alert 250804.84: Global MASTER-Net observations report
  92. GRB 250806A: EP-FXT observation
  93. EP#01709198415/EP250806a: Swift-XRT observations
  94. EP250806a: Global MASTER-Net observations report
  95. EP250802a: EP-FXT follow-up observation
  96. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  97. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  98. EP250806a: SVOM /VT optical candidate
  99. GRB 250806A: J-band upper limit from WINTER
  100. GRB 250805A: Swift-BAT refined analysis

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