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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. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  2. GRB 251016A: SVOM/ECLAIRs refined analysis
  3. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  5. Fermi-LAT gamma-ray observations of IceCube-251018A
  6. GRB 251017A : RAPAS follow-up observations
  7. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 251017A: COLIBRÍ optical observations of a late plateau
  9. IceCube-251018A: DDOTI Optical Upper Limit
  10. GRB 251017A: Swift-BAT refined analysis
  11. GRB 251016A: Fermi GBM Observation
  12. GRB 251018A: Fermi GBM Observation
  13. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  14. GRB 251018A: Swift-XRT refined Analysis
  15. GRB 251018A: Enhanced Swift-XRT position
  16. Fermi trigger No 782500909: Global MASTER-Net observations report
  17. GRB 251016A: HXMT/HE detection
  18. IceCube-251018A: Global MASTER-Net observations report
  19. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  20. GRB 251016A: Swift-XRT afterglow detection
  21. GRB 251017A: Swift/UVOT Detection
  22. GRB 251016A: Swift/UVOT Detection
  23. GRB 251018A: Swift/UVOT Detection
  24. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  25. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  26. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  27. GRB 251016A: VLT/FORS2 Optical Observation
  28. GRB 251017A: COLIBRÍ photometric redshift
  29. GRB 251017A: Swift-XRT refined Analysis
  30. GRB 251018A: MASTER OT detection
  31. GRB 251018A: TRT optical afterglow detection
  32. Swift GRB 251018A: Global MASTER-Net observations report
  33. GRB 251018A: Swift detection of a burst with an optical counterpart
  34. GRB 251018A: Fermi GBM Final Real-time Localization
  35. GRB 251017A: SVOM/VT optical observation
  36. GRB 251011A: Fermi GBM Observation
  37. GRB 251017A: OHP/T193 i-band observations
  38. GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
  39. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  40. GRB 251017A: J-band detection with WINTER
  41. GRB 251017A: Glowbug gamma-ray detection
  42. GRB 251013C: Liverpool Telescope observations
  43. GRB 251013C: Leavitt Observatory optical photometry
  44. Fermi GRB 251016B: Global MASTER-Net observations report
  45. GRB 251017A: JinShan observations of the optical afterglow
  46. Swift GRB 251017A: Global MASTER-Net observations report
  47. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  48. Swift Trigger 1404295 is not a GRB
  49. GRB 251016A: AstroSat CZTI detection of a short burst
  50. GRB 251017A: Enhanced Swift-XRT position
  51. GRB 251017A: COLIBRÍ Early Afterglow Detection
  52. GRB 251016B: AstroSat CZTI detection
  53. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  54. GRB 251017A: Swift detection of a burst with an optical counterpart
  55. GRB 251016A: CALET Gamma-Ray Burst Monitor detection
  56. GRB 251016B: CALET Gamma-Ray Burst Monitor detection
  57. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  58. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  59. GRB 251007B: Swift-BAT refined analysis
  60. GRB 251016B: Fermi GBM Final Real-time Localization
  61. GRB 251014D: Swift-BAT refined analysis
  62. GRB 251016A: BOOTES-6/DPRT optical upper limit
  63. GRB 251016A: Glowbug gamma-ray detection of a short burst
  64. GRB 251013C: VLA detection
  65. sb25101602: Swift-XRT counterpart detection
  66. Fermi GRB 251016A: Global MASTER-Net observations report
  67. GRB 251016A: Fermi GBM Final Localization
  68. GRB 251016A: SVOM detection of a short burst
  69. GRB 251014A: Swift-XRT observations
  70. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  71. GRB 251014B: PRIME J-band upper limit
  72. Upper limits from a search for additional neutrino events in IceCube
  73. IceCube Alert 251014.77: Global MASTER-Net observations report
  74. Swift GRB251015.60: Global MASTER-Net observations report
  75. GRB 251013C: Kilonova-Catcher optical afterglow detection
  76. Fermi-LAT Gamma-ray Observations of IceCube-251014A
  77. GRB 251013D: Swift/UVOT Observations
  78. GRB 251013C: Swift/UVOT Detection
  79. Konus-Wind detection of GRB 251007A
  80. Fermi Gamma-ray Burst Monitor trigger 782237334/251015673 is not a GRB
  81. GRB 251013C, GCN Circular 42267, errata corrige
  82. GRB 251013C: detection of a radio counterpart at 15.5GHz
  83. GRB 251015A: Fermi GBM Final Real-time Localization
  84. GRB 251013C: SVOM/ECLAIRs refined analysis
  85. GRB 251013D: Swift-XRT observations
  86. Swift Trigger 1404295: possible GRB 251015A
  87. GRB 251014B: Swift-XRT observations
  88. GRB 251014B: Swift/UVOT Upper Limits
  89. GRB 251014B: VLT/FORS2 Optical Observation
  90. GRB 251014D: Swift/UVOT Upper Limits
  91. GRB 251014D: BOOTES-6/DPRT optical upper limit
  92. GRB 251014D: Swift-XRT afterglow detection
  93. GRB 251013C: MAO/AZT-22 optical observations
  94. GRB 251011B: SVOM/VT optical upper limit
  95. GRB 251013C: Swift ToO observations
  96. GRB 251013D: Fermi GBM Observation
  97. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  98. GRB 251014A: Swift-BAT refined analysis
  99. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  100. GRB 251013C: OHP/T193 further optical observations and possible color evolution

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