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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"

45437 results found.

  1. EP 250807.979: GOTO optical upper limit
  2. EP250807a: COLIBRÍ optical upper limit
  3. GRB 250807A: SVOM/VT optical observation
  4. EP250806a: Upper limit from Fermi-GBM Observations
  5. GRB 250807B: Enhanced Swift-XRT position
  6. Swift GRB250807.65: Global MASTER-Net observations report
  7. GRB 250807A: Enhanced Swift-XRT position
  8. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 250807B: Swift detection of a burst with an optical counterpart.
  10. GRB 250805A: Kilonova-Catcher optical upper limits
  11. EP250806a:SVOM/VT refined analysis
  12. GRB 250805A: Swift/UVOT Upper Limits
  13. GRB 250806A: Swift/UVOT U-band detection
  14. EP250806a: Liverpool telescope optical upper limit
  15. GRB 250807A: Swift detection of a burst with an optical counterpart
  16. IceCube Alert 250804.84: Global MASTER-Net observations report
  17. GRB 250806A: EP-FXT observation
  18. EP#01709198415/EP250806a: Swift-XRT observations
  19. EP250806a: Global MASTER-Net observations report
  20. EP250802a: EP-FXT follow-up observation
  21. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  22. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  23. EP250806a: SVOM /VT optical candidate
  24. GRB 250806A: J-band upper limit from WINTER
  25. GRB 250805A: Swift-BAT refined analysis
  26. GRB 250806A: KAIT optical upper limit
  27. GRB 250806A: SVOM/VT refined analysis
  28. GRB 250806A: Swift-XRT counterpart detection
  29. EP250806a: COLIBRÍ optical upper limit
  30. GRB 250806A: Kilonova-Catcher optical upper limits
  31. EP250806a: Einstein Probe detection of an X-ray transient
  32. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  33. GRB 250806A: SVOM/VT optical upper limit
  34. GRB 250806A: SVOM detection of a soft burst
  35. GRB 250805A: SVOM/VT optical counterpart
  36. GRB 250805A: ESO/VLT observations
  37. GRB 250805A: Swift-XRT refined Analysis
  38. GRB 250804B: Swift-XRT observations
  39. GRB 250805A: Enhanced Swift-XRT position
  40. GRB 250804C: AstroSat CZTI detection of a long burst
  41. GRB 250805A: TRT optical upper limits
  42. IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
  43. GRB 250805A: Swift-XRT observations
  44. GRB 250805A: Swift detection of a burst
  45. Swift GRB250805.26: Global MASTER-Net observations report
  46. GRB 250804B: Tiled Swift observations
  47. Fermi trigger No 776041355: Global MASTER-Net observations report
  48. GRB 250804B: SVOM/GRM observation of a short burst
  49. GRB 250804A: Fermi GBM Final Localization
  50. EP250802a: additional Liverpool Telescope upper limits
  51. EP250730a: SVOM/VT optical upper limit
  52. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  53. EP250802a: Liverpool Telescope optical upper limits
  54. EP250802a: Global MASTER-Net observations report
  55. EP250802a: GROWTH-India Telescope optical upper limit
  56. EP250802a: Einstein Probe detection of an X-ray transient
  57. LIGO/Virgo/KAGRA S250802dn: Updated Sky localization
  58. The EP-WXT trigger 01709198251 is likely a flaring star
  59. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  60. The EP-WXT trigger 01709198202 is likely a flaring star
  61. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  62. GRB 250702B: SMA observations
  63. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  64. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  65. EP250711a: CrAO and Assy optical observations
  66. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  67. EP250730a: Global MASTER-Net observations report
  68. EP250730a: COLIBRÍ optical upper limit
  69. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  70. EP250730a: Einstein Probe detection of an X-ray transient
  71. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  72. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  73. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  74. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  75. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  76. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  77. GRB 250725A: AstroSat CZTI detection
  78. GRB 250727A: EP-FXT follow-up observation
  79. GRB 250725A: PRIME near-infrared observations
  80. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  81. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  82. GRB: Clarification on Gamma-Ray Burst Naming Convention
  83. GRB 250728A: Swift-XRT observations
  84. GRB 250727A: SVOM/ECLAIRs refined analysis
  85. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  86. GRB 250728A: COLIBRÍ optical upper limit
  87. GRB 250728A: Fermi GBM Observation
  88. Fermi trigger No 775387550: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  90. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  91. GRB 250728A: Swift ToO observations
  92. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  93. GRB 250727A: AST3-2 Upper limit
  94. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  95. GRB 250727A: EP-FXT counterpart detection
  96. GRB250727A: SVOM/VT optical upper limit
  97. GRB 250727A: Swift-XRT observations
  98. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  100. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates

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