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

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