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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 251025B: Swift-XRT afterglow detection
  2. GRB 251024A: Swift-BAT refined analysis
  3. IceCube Alert 251025.57: Global MASTER-Net observations report
  4. GRB 251024A: Swift-XRT refined Analysis
  5. GRB 251025A (sb25102501): stellar flare confirmed
  6. GRB 251025B: SVOM/VT optical observations with VHF data
  7. GRB 251025B: MASTER OT detection
  8. GRB 251025B: SVOM/C-GFT optical counterpart detection
  9. GRB 251025B: SVOM detection of a burst
  10. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  12. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  13. GRB 251025A: SVOM/VT VHF optical upper limit
  14. GRB 251025A: SVOM detection of a faint burst
  15. GRB 251003A: VLA Detection
  16. GRB 251024A: Enhanced Swift-XRT position
  17. GRB 251023C: Glowbug gamma-ray detection
  18. GRB 251024A: LCOGT Optical Afterglow Detection
  19. GRB 251022A: KAIT optical observations
  20. GRB 251024A: Swift detection of a burst
  21. Swift GRB 251024A: Global MASTER-Net observations report
  22. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  23. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  24. EP251023a: MAO/AZT-22 optical observations
  25. GRB 251023B: OHP/T193 optical observations
  26. EP251023a: OHP/T193 optical observations
  27. GRB 251023C: AstroSat CZTI detection
  28. EP251023b/GRB 251023B: JinShan optical observation
  29. GRB 251022A: Swift-XRT detection of GOTO25iym
  30. EP251023b: Global MASTER-Net observations report
  31. EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
  32. GRB 251023C: CALET Gamma-Ray Burst Monitor detection
  33. GRB 251022A: GROWTH-India Telescope optical observations
  34. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  35. EP251023a: GROWTH-India Telescope optical observations
  36. GRB 251022A: Fermi GBM Observation
  37. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  38. GRB 251023A: Glowbug gamma-ray detection
  39. GRB 251023B: Glowbug gamma-ray detection
  40. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  41. EP251023a: Global MASTER-Net observations report
  42. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  43. IPN triangulation of GRB 251016B
  44. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  45. EP#01709247298: Swift-XRT counterpart detection
  46. EP251023a: COLIBRÍ optical observations
  47. GRB 251013C: further SAO RAS optical observations
  48. EP251023a: Keck/LRIS spectroscopic redshift z=2.232
  49. GRB 251022A: COLIBRÍ optical observations
  50. GRB 251013C: ISON-Castelgrande observatory optical observations
  51. GRB 251022A: MASTER OT detection
  52. GRB 251022A: DDOTI Optical Detection
  53. EP251021b/GRB 251021A: SVOM/VT optical candidate
  54. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  55. EP251023a: NOT optical counterpart detection
  56. Fermi GRB 251023A: Global MASTER-Net observations report
  57. EP251023a: GSP Optical Counterpart Detection
  58. EP251023a: Einstein Probe detection of an X-ray transient
  59. EP/WXT 01709247295: GOTO optical afterglow candidate.
  60. GRB 251022A: GOTO optical counterpart detection
  61. GRB 251023A: Fermi GBM Final Localization Correction
  62. GRB 251022A: Fermi-LAT detection
  63. GRB 251016B: Fermi GBM Detection
  64. GRB 251022A: Tiled Swift observations
  65. LAT GRB251022A: Global MASTER-Net observations report
  66. GRB 251022A: Fermi GBM Final Real-time Localization
  67. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  68. EP251021b: BOOTES-7 optical upper limit
  69. EP251021b: Einstein Probe detection of a fast X-ray transient
  70. GRB 250911A: MAXI/GSC detection
  71. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  72. GRB 251016A: SVOM/ECLAIRs refined analysis
  73. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  75. Fermi-LAT gamma-ray observations of IceCube-251018A
  76. GRB 251017A : RAPAS follow-up observations
  77. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  78. GRB 251017A: COLIBRÍ optical observations of a late plateau
  79. IceCube-251018A: DDOTI Optical Upper Limit
  80. GRB 251017A: Swift-BAT refined analysis
  81. GRB 251016A: Fermi GBM Observation
  82. GRB 251018A: Fermi GBM Observation
  83. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  84. GRB 251018A: Swift-XRT refined Analysis
  85. GRB 251018A: Enhanced Swift-XRT position
  86. Fermi trigger No 782500909: Global MASTER-Net observations report
  87. GRB 251016A: HXMT/HE detection
  88. IceCube-251018A: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  90. GRB 251016A: Swift-XRT afterglow detection
  91. GRB 251017A: Swift/UVOT Detection
  92. GRB 251016A: Swift/UVOT Detection
  93. GRB 251018A: Swift/UVOT Detection
  94. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  95. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  96. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  97. GRB 251016A: VLT/FORS2 Optical Observation
  98. GRB 251017A: COLIBRÍ photometric redshift
  99. GRB 251017A: Swift-XRT refined Analysis
  100. GRB 251018A: MASTER OT detection

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