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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"

26164 results found.

  1. The EP-WXT trigger 01709247588 is likely a flaring star
  2. GRB 251028B: Fermi/GBM observation
  3. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  4. GRB 251028B: CALET Gamma-Ray Burst Monitor detection
  5. Fermi GRB 251028B: Global MASTER-Net observations report
  6. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  7. GRB 251028B: Fermi GBM Final Localization Correction
  8. GRB251026B: PRIME H-band upper limit
  9. GRB251025B: 3.6m DOT Optical Observations
  10. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  11. GRB 251028A: Fermi GBM Final Real-time Localization
  12. The EP-WXT trigger 01709247525 is not a real source
  13. SVOM trigger sb25102702/GRB 251027A is not a GRB
  14. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  15. GRB 251027A: Swift-XRT observations
  16. EP251027.145: COLIBRÍ optical upper limits
  17. GRB 251022A: SVOM/GRM observation
  18. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  19. GRB 251027A: LCO optical upper limit
  20. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 251025B: Kilonova-Catcher optical afterglow detection
  22. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  23. GRB 251027A: SVOM detection of a faint burst
  24. GRB 251026B: Tentative GOTO optical counterpart candidate
  25. GRB 251025C: CALET Gamma-Ray Burst Monitor detection
  26. Fermi GRB 251026B: Global MASTER-Net observations report
  27. Fermi GRB 251025C: Global MASTER-Net observations report
  28. GRB 251026A: Swift-XRT observations
  29. GRB 251025B: J-band detection with WINTER
  30. IceCube-251025A: DDOTI Optical Upper Limit
  31. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. GRB 251026B: Fermi GBM Final Localization
  33. GRB 251026A: SVOM detection of a long burst
  34. GRB 251025B: SVOM/VT optical bump
  35. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  36. GRB 251023A: SVOM/GRM observation
  37. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  38. GRB 251025C: Fermi GBM Final Real-time Localization
  39. GRB 251025B: GROWTH-India Telescope optical observations
  40. GRB 251024A: Swift/UVOT Upper Limits
  41. GRB 251024A: Swift-BAT refined analysis
  42. IceCube Alert 251025.57: Global MASTER-Net observations report
  43. GRB 251024A: Swift-XRT refined Analysis
  44. GRB 251025A (sb25102501): stellar flare confirmed
  45. GRB 251025B: SVOM/VT optical observations with VHF data
  46. GRB 251025B: SVOM/C-GFT optical counterpart detection
  47. GRB 251025B: SVOM detection of a burst
  48. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  49. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. GRB 251025A: SVOM/VT VHF optical upper limit
  51. GRB 251025A: SVOM detection of a faint burst
  52. GRB 251024A: LCOGT Optical Afterglow Detection
  53. GRB 251024A: Swift detection of a burst
  54. Swift GRB 251024A: Global MASTER-Net observations report
  55. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  56. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  57. EP251023a: MAO/AZT-22 optical observations
  58. EP251023b/GRB 251023B: JinShan optical observation
  59. EP251023b: Global MASTER-Net observations report
  60. EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
  61. GRB 251023C: CALET Gamma-Ray Burst Monitor detection
  62. GRB 251022A: GROWTH-India Telescope optical observations
  63. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  64. EP251023a: GROWTH-India Telescope optical observations
  65. GRB 251022A: Fermi GBM Observation
  66. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  67. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  68. EP251023a: Global MASTER-Net observations report
  69. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  70. IPN triangulation of GRB 251016B
  71. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  72. EP#01709247298: Swift-XRT counterpart detection
  73. EP251023a: COLIBRÍ optical observations
  74. EP251023a: Keck/LRIS spectroscopic redshift z=2.232
  75. GRB 251022A: COLIBRÍ optical observations
  76. GRB 251013C: ISON-Castelgrande observatory optical observations
  77. GRB 251022A: MASTER OT detection
  78. GRB 251022A: DDOTI Optical Detection
  79. EP251021b/GRB 251021A: SVOM/VT optical candidate
  80. EP251023a: NOT optical counterpart detection
  81. Fermi GRB 251023A: Global MASTER-Net observations report
  82. EP251023a: GSP Optical Counterpart Detection
  83. EP251023a: Einstein Probe detection of an X-ray transient
  84. EP/WXT 01709247295: GOTO optical afterglow candidate.
  85. GRB 251022A: GOTO optical counterpart detection
  86. GRB 251023A: Fermi GBM Final Localization Correction
  87. GRB 251022A: Fermi-LAT detection
  88. GRB 251016B: Fermi GBM Detection
  89. LAT GRB251022A: Global MASTER-Net observations report
  90. GRB 251022A: Fermi GBM Final Real-time Localization
  91. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  92. EP251021b: BOOTES-7 optical upper limit
  93. EP251021b: Einstein Probe detection of a fast X-ray transient
  94. GRB 251016A: SVOM/ECLAIRs refined analysis
  95. GRB 251017A: COLIBRÍ optical observations of a late plateau
  96. IceCube-251018A: DDOTI Optical Upper Limit
  97. GRB 251017A: Swift-BAT refined analysis
  98. GRB 251016A: Fermi GBM Observation
  99. GRB 251018A: Fermi GBM Observation
  100. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections

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