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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"

45439 results found.

  1. GRB 250807A: Enhanced Swift-XRT position
  2. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  3. GRB 250807B: Swift detection of a burst with an optical counterpart.
  4. GRB 250805A: Kilonova-Catcher optical upper limits
  5. EP250806a:SVOM/VT refined analysis
  6. GRB 250805A: Swift/UVOT Upper Limits
  7. GRB 250806A: Swift/UVOT U-band detection
  8. EP250806a: Liverpool telescope optical upper limit
  9. GRB 250807A: Swift detection of a burst with an optical counterpart
  10. IceCube Alert 250804.84: Global MASTER-Net observations report
  11. GRB 250806A: EP-FXT observation
  12. EP#01709198415/EP250806a: Swift-XRT observations
  13. EP250806a: Global MASTER-Net observations report
  14. EP250802a: EP-FXT follow-up observation
  15. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  16. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  17. EP250806a: SVOM /VT optical candidate
  18. GRB 250806A: J-band upper limit from WINTER
  19. GRB 250805A: Swift-BAT refined analysis
  20. GRB 250806A: KAIT optical upper limit
  21. GRB 250806A: SVOM/VT refined analysis
  22. GRB 250806A: Swift-XRT counterpart detection
  23. EP250806a: COLIBRÍ optical upper limit
  24. GRB 250806A: Kilonova-Catcher optical upper limits
  25. EP250806a: Einstein Probe detection of an X-ray transient
  26. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 250806A: SVOM/VT optical upper limit
  28. GRB 250806A: SVOM detection of a soft burst
  29. GRB 250805A: SVOM/VT optical counterpart
  30. GRB 250805A: ESO/VLT observations
  31. GRB 250805A: Swift-XRT refined Analysis
  32. GRB 250804B: Swift-XRT observations
  33. GRB 250805A: Enhanced Swift-XRT position
  34. GRB 250804C: AstroSat CZTI detection of a long burst
  35. GRB 250805A: TRT optical upper limits
  36. IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 250805A: Swift-XRT observations
  38. GRB 250805A: Swift detection of a burst
  39. Swift GRB250805.26: Global MASTER-Net observations report
  40. GRB 250804B: Tiled Swift observations
  41. Fermi trigger No 776041355: Global MASTER-Net observations report
  42. GRB 250804B: SVOM/GRM observation of a short burst
  43. GRB 250804A: Fermi GBM Final Localization
  44. EP250802a: additional Liverpool Telescope upper limits
  45. EP250730a: SVOM/VT optical upper limit
  46. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  47. EP250802a: Liverpool Telescope optical upper limits
  48. EP250802a: Global MASTER-Net observations report
  49. EP250802a: GROWTH-India Telescope optical upper limit
  50. EP250802a: Einstein Probe detection of an X-ray transient
  51. LIGO/Virgo/KAGRA S250802dn: Updated Sky localization
  52. The EP-WXT trigger 01709198251 is likely a flaring star
  53. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  54. The EP-WXT trigger 01709198202 is likely a flaring star
  55. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  56. GRB 250702B: SMA observations
  57. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  58. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  59. EP250711a: CrAO and Assy optical observations
  60. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  61. EP250730a: Global MASTER-Net observations report
  62. EP250730a: COLIBRÍ optical upper limit
  63. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  64. EP250730a: Einstein Probe detection of an X-ray transient
  65. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  66. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  67. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  68. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  69. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  70. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  71. GRB 250725A: AstroSat CZTI detection
  72. GRB 250727A: EP-FXT follow-up observation
  73. GRB 250725A: PRIME near-infrared observations
  74. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  75. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  76. GRB: Clarification on Gamma-Ray Burst Naming Convention
  77. GRB 250728A: Swift-XRT observations
  78. GRB 250727A: SVOM/ECLAIRs refined analysis
  79. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  80. GRB 250728A: COLIBRÍ optical upper limit
  81. GRB 250728A: Fermi GBM Observation
  82. Fermi trigger No 775387550: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  84. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  85. GRB 250728A: Swift ToO observations
  86. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  87. GRB 250727A: AST3-2 Upper limit
  88. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  89. GRB 250727A: EP-FXT counterpart detection
  90. GRB250727A: SVOM/VT optical upper limit
  91. GRB 250727A: Swift-XRT observations
  92. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  95. GRB 250727A: SVOM detection of a burst
  96. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  97. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  98. The EP-WXT trigger 01709195487 is likely a flaring star
  99. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  100. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate

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