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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. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  2. GRB 250813B: Swift-XRT afterglow detection
  3. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  4. GRB 250814A: Fermi GBM Final Real-time Localization
  5. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  6. GRB 250813B: Ondrejov D50 fast decay
  7. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  8. GRB 250813B: Ondrejov D50 optical afterglow detection
  9. GRB 250813B: SVOM detection of a bright long burst
  10. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  11. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  12. EP250812a: Nickel optical upper limit
  13. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  14. GRB 250812A: NTT spectroscopic redshift z = 2.57
  15. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  16. EP250812a: NOT, NTT, and GS observations
  17. GRB 250812A: Swift/UVOT Detection
  18. GRB 250813A: Fermi GBM Final Localization
  19. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  20. EP250812a: Liverpool Telescope upper limits
  21. EP250812a: SVOM/VT optical counterpart
  22. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  23. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  24. IceCube Alert 250813.14: Global MASTER-Net observations report
  25. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  26. GRB 250812A: EP-FXT counterpart detection
  27. GRB 250812A: Swift ToO observations
  28. GRB 250807B: Swift-BAT refined analysis
  29. EP 250812a: GOTO optical upper limit
  30. GRB 250812A: Kilonova-Catcher optical afterglow detection
  31. EP250812a: Swift-XRT counterpart detection
  32. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  33. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  34. EP250812a: Einstein Probe detection of an X-ray transient
  35. GRB 250812A: SVOM/VT optical afterglow confirmation
  36. GRB 250812A: Swift-XRT afterglow detection
  37. GRB 250812A: TRT likely optical counterpart detection
  38. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  39. GRB 250812A: SVOM detection of a faint long burst
  40. GRB 250809A: Swift-BAT refined analysis
  41. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  42. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  43. GRB 250807A: Swift-BAT refined analysis
  44. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  45. GRB 250809A: Swift/UVOT Detection
  46. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  47. Corrected Swift-XRT Refined Analysis of GRB 250809A
  48. GRB 250809A: Swift-XRT refined Analysis
  49. GRB 250807B: SVOM/VT optical observation
  50. EP250807a: EP-FXT follow-up observation upper limit
  51. GRB 250809A: LCOGT Optical Upper Limits
  52. GRB 250702B: Chandra X-ray Detection
  53. EP250807a: Global MASTER-Net observations report
  54. Fermi GRB 250808A: Global MASTER-Net observations report
  55. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  56. GRB 250808A: VLT X-shooter candidate counterpart
  57. GRB 250809A: Prompt enhanced Swift-XRT position
  58. GRB 250809A: Swift detection of a gamma ray burst
  59. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. GRB 250808A: Fermi GBM Observation
  61. GRB 250808A: Swift-XRT candidate counterpart detection
  62. GRB 250807A: SVOM/VT optical continued observation
  63. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  64. GRB 250808A: SVOM detection of a long burst
  65. GRB 250808A: Fermi GBM Final Real-time Localization
  66. Konus-Wind detection of GRB 250807A
  67. GRB 250807B: Swift/UVOT Detection
  68. GRB 250807B: Kilonova-Catcher optical afterglow detection
  69. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 250807A: Swift/UVOT Detection
  71. GRB 250807A: Swift-XRT refined Analysis
  72. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  73. GRB 250806A: SVOM/MXT refined analysis
  74. GRB 250806A: SVOM/ECLAIRs refined analysis
  75. EP250807a: NTT z-band optical upper limit
  76. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  77. GRB 250804B: Insight-HXMT detection
  78. GRB 250807A: SVOM/GRM observation
  79. Swift GRB250807.45: Global MASTER-Net observations report
  80. GRB 250807A: AstroSat CZTI detection of bright long burst
  81. GRB 250807B: Swift-XRT refined Analysis
  82. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  83. GRB 250807B: NTT optical observations
  84. EP250807a: EP-WXT detection of a fast X-ray transient
  85. EP 250807.979: GOTO optical upper limit
  86. EP250807a: COLIBRÍ optical upper limit
  87. GRB 250807A: SVOM/VT optical observation
  88. EP250806a: Upper limit from Fermi-GBM Observations
  89. GRB 250807B: Enhanced Swift-XRT position
  90. Swift GRB250807.65: Global MASTER-Net observations report
  91. GRB 250807A: Enhanced Swift-XRT position
  92. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  93. GRB 250807B: Swift detection of a burst with an optical counterpart.
  94. GRB 250805A: Kilonova-Catcher optical upper limits
  95. EP250806a:SVOM/VT refined analysis
  96. GRB 250805A: Swift/UVOT Upper Limits
  97. GRB 250806A: Swift/UVOT U-band detection
  98. EP250806a: Liverpool telescope optical upper limit
  99. GRB 250807A: Swift detection of a burst with an optical counterpart
  100. IceCube Alert 250804.84: Global MASTER-Net observations report

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