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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"

25666 results found.

  1. Fermi trigger No 784717756: Global MASTER-Net observations report
  2. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  3. The EP-WXT trigger 01709248221 is likely a flaring star
  4. Fermi GRB 251114A: Global MASTER-Net observations report
  5. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  6. GRB 251114A: Fermi GBM Final Real-time Localization
  7. Fermi GRB 251113A: Global MASTER-Net observations report
  8. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  9. GRB 251113A: Fermi GBM Final Real-time Localization
  10. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  11. GRB 251112A: Swift/UVOT Upper Limits
  12. GRB 251112A: Swift-XRT refined Analysis
  13. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  14. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  15. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  16. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  17. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  18. Swift Trigger 1413695: a possible GRB 251112A
  19. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  20. Fermi trigger No 784621743: Global MASTER-Net observations report
  21. Fermi Gamma-ray Burst Monitor trigger 784653403/251112637 is not a GRB
  22. GRB251111A: 1.3m DFOT optical upper limit
  23. SVOM GRB251111.42: Global MASTER-Net observations report
  24. GRB 251111A: Swift-XRT observations
  25. SVOM GRB251111.22: Global MASTER-Net observations report
  26. GRB 251111A: EP-FXT counterpart detection
  27. GRB 251013C: Chandra X-ray observations and jet break detection
  28. GRB 251111A: LCO optical observation
  29. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  30. GRB 251111A: SVOM detection of a soft burst
  31. GRB 251103B: Swift-BAT refined analysis
  32. GRB 251106A: Swift/UVOT Upper Limits
  33. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  34. GRB 251105A: AstroSat CZTI detection
  35. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  36. GRB 251108A: Fermi GBM Final Localization Correction
  37. Fermi trigger No 784329591: Global MASTER-Net observations report
  38. Fermi trigger No 784279167: Global MASTER-Net observations report
  39. SVOM GRB251108.54: Global MASTER-Net observations report
  40. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  41. The EP-WXT trigger 01709248051 is likely a flaring star
  42. SVOM GRB251106.83: Global MASTER-Net observations report
  43. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  44. GRB 251106B: SVOM/GRM observation of a short burst
  45. GRB 251106A: Kilonova-Catcher optical upper limit
  46. Fermi GBM Sub-Threshold Detection of GRB 251106A
  47. GRB 251106A: Swift/BAT arcminute localization of a burst
  48. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  49. GRB 251106A: MASTER optical observations
  50. GRB 251106A: SVOM detection of a burst
  51. GRB 251103B: AstroSat CZTI detection
  52. GRB 250920C: TERI Gamma-ray detection
  53. Fermi trigger No 784034269: Global MASTER-Net observations report
  54. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  55. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  56. GRB 251105A: Fermi GBM Observation
  57. GRB 251105C: Fermi GBM Final Localization Correction
  58. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  59. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  60. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  61. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  62. Fermi GBM Sub-Threshold Detection of GRB 251105B
  63. GRB 251103B: Swift/UVOT Upper Limits
  64. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  65. Fermi GRB 251105A: Global MASTER-Net observations report
  66. GRB 251105A: Fermi GBM Final Real-time Localization
  67. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  68. GRB 251103B: Fermi GBM observation
  69. GRB 251104A: SVOM detection of a burst
  70. EP251102a: FTW optical and NIR observations
  71. GRB 251103A: WFST optical observations
  72. GRB 251103A: Xinglong 2.16m optical detection
  73. GRB 251103B: Nanshan/HMT optical upper limit
  74. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  75. GRB 251103B: MITSuME Akeno optical upper limits
  76. GRB 251103B: Swift-XRT refined Analysis
  77. Fermi GRB 251103A: Global MASTER-Net observations report
  78. EP251102a: NIR observations with WINTER
  79. GRB 251103A: J-band detection with WINTER
  80. Swift GRB 251103B: Global MASTER-Net observations report
  81. GRB 251103B: GROWTH-India Telescope optical upper limits
  82. GRB 251103B: Swift detection of a burst
  83. GRB 251103B: Fermi GBM Final Real-time Localization
  84. GRB 251103A: Swift/UVOT Detection
  85. GRB 251103A: Fermi GBM Observation
  86. GRB 251103A: SVOM/GRM observation
  87. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  88. EP251102a: Einstein Probe detection of a fast X-ray transient
  89. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  90. GRB 251103A: LCO optical observation
  91. EP251102.890: COLIBRÍ optical counterpart candidate
  92. GRB 251103A: GOTO optical afterglow detection
  93. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  94. GRB 251103A: BOOTES-2/TELMA optical afterglow
  95. GRB 251103A: LCO optical afterglow detection
  96. GRB 251103A: Fermi GBM Final Localization
  97. GRB 251103A: NOT optical afterglow candidate
  98. GRB 251103A: SVOM detection of a bright burst
  99. GRB 251102B: Fermi GBM Final Real-time Localization
  100. Fermi GRB 251102A: Global MASTER-Net observations report

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