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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"

45426 results found.

  1. GRB 250814A: Fermi GBM Final Real-time Localization
  2. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  3. GRB 250813B: Ondrejov D50 fast decay
  4. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  5. GRB 250813B: Ondrejov D50 optical afterglow detection
  6. GRB 250813B: SVOM detection of a bright long burst
  7. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  8. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  9. EP250812a: Nickel optical upper limit
  10. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  11. GRB 250812A: NTT spectroscopic redshift z = 2.57
  12. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  13. EP250812a: NOT, NTT, and GS observations
  14. GRB 250812A: Swift/UVOT Detection
  15. GRB 250813A: Fermi GBM Final Localization
  16. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  17. EP250812a: Liverpool Telescope upper limits
  18. EP250812a: SVOM/VT optical counterpart
  19. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  20. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  21. IceCube Alert 250813.14: Global MASTER-Net observations report
  22. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  23. GRB 250812A: EP-FXT counterpart detection
  24. GRB 250812A: Swift ToO observations
  25. GRB 250807B: Swift-BAT refined analysis
  26. EP 250812a: GOTO optical upper limit
  27. GRB 250812A: Kilonova-Catcher optical afterglow detection
  28. EP250812a: Swift-XRT counterpart detection
  29. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  30. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  31. EP250812a: Einstein Probe detection of an X-ray transient
  32. GRB 250812A: SVOM/VT optical afterglow confirmation
  33. GRB 250812A: Swift-XRT afterglow detection
  34. GRB 250812A: TRT likely optical counterpart detection
  35. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  36. GRB 250812A: SVOM detection of a faint long burst
  37. GRB 250809A: Swift-BAT refined analysis
  38. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  39. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  40. GRB 250807A: Swift-BAT refined analysis
  41. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  42. GRB 250809A: Swift/UVOT Detection
  43. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  44. Corrected Swift-XRT Refined Analysis of GRB 250809A
  45. GRB 250809A: Swift-XRT refined Analysis
  46. GRB 250807B: SVOM/VT optical observation
  47. EP250807a: EP-FXT follow-up observation upper limit
  48. GRB 250809A: LCOGT Optical Upper Limits
  49. GRB 250702B: Chandra X-ray Detection
  50. EP250807a: Global MASTER-Net observations report
  51. Fermi GRB 250808A: Global MASTER-Net observations report
  52. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  53. GRB 250808A: VLT X-shooter candidate counterpart
  54. GRB 250809A: Prompt enhanced Swift-XRT position
  55. GRB 250809A: Swift detection of a gamma ray burst
  56. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  57. GRB 250808A: Fermi GBM Observation
  58. GRB 250808A: Swift-XRT candidate counterpart detection
  59. GRB 250807A: SVOM/VT optical continued observation
  60. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  61. GRB 250808A: SVOM detection of a long burst
  62. GRB 250808A: Fermi GBM Final Real-time Localization
  63. Konus-Wind detection of GRB 250807A
  64. GRB 250807B: Swift/UVOT Detection
  65. GRB 250807B: Kilonova-Catcher optical afterglow detection
  66. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 250807A: Swift/UVOT Detection
  68. GRB 250807A: Swift-XRT refined Analysis
  69. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  70. GRB 250806A: SVOM/MXT refined analysis
  71. GRB 250806A: SVOM/ECLAIRs refined analysis
  72. EP250807a: NTT z-band optical upper limit
  73. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  74. GRB 250804B: Insight-HXMT detection
  75. GRB 250807A: SVOM/GRM observation
  76. Swift GRB250807.45: Global MASTER-Net observations report
  77. GRB 250807A: AstroSat CZTI detection of bright long burst
  78. GRB 250807B: Swift-XRT refined Analysis
  79. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  80. GRB 250807B: NTT optical observations
  81. EP250807a: EP-WXT detection of a fast X-ray transient
  82. EP 250807.979: GOTO optical upper limit
  83. EP250807a: COLIBRÍ optical upper limit
  84. GRB 250807A: SVOM/VT optical observation
  85. EP250806a: Upper limit from Fermi-GBM Observations
  86. GRB 250807B: Enhanced Swift-XRT position
  87. Swift GRB250807.65: Global MASTER-Net observations report
  88. GRB 250807A: Enhanced Swift-XRT position
  89. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  90. GRB 250807B: Swift detection of a burst with an optical counterpart.
  91. GRB 250805A: Kilonova-Catcher optical upper limits
  92. EP250806a:SVOM/VT refined analysis
  93. GRB 250805A: Swift/UVOT Upper Limits
  94. GRB 250806A: Swift/UVOT U-band detection
  95. EP250806a: Liverpool telescope optical upper limit
  96. GRB 250807A: Swift detection of a burst with an optical counterpart
  97. IceCube Alert 250804.84: Global MASTER-Net observations report
  98. GRB 250806A: EP-FXT observation
  99. EP#01709198415/EP250806a: Swift-XRT observations
  100. EP250806a: Global MASTER-Net observations report

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