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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"

5089 results found.

  1. Fermi GRB 260115A: Global MASTER-Net observations report
  2. GRB260114A: STEP/T80S optical limits
  3. GRB 251222A: radio detection with the VLA
  4. GRB 260114A: COLIBRÍ optical upper limits
  5. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  6. GRB 260111A: GOTO optical upper limits
  7. Swift trigger 1436759 is not an astrophysical event
  8. GRB 260109A: Fermi GBM Final Real-time Localization
  9. Fermi GRB 260107A: Global MASTER-Net observations report
  10. GRB 260102A: AbAO optical observations
  11. Fermi GRB 260105A: Global MASTER-Net observations report
  12. Fermi GRB 260105B: Global MASTER-Net observations report
  13. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  14. GRB 260101A: COLIBRÍ optical upper limits
  15. EP260105a: Global MASTER-Net observations report
  16. Fermi GRB 260104B: Global MASTER-Net observations report
  17. GRB 260101A: COLIBRÍ optical observations
  18. SVOM GRB260103.08: Global MASTER-Net observations report
  19. GRB 260102B: Fermi GBM Final Real-time Localization
  20. Fermi GBM Sub-Threshold Detection of GRB 260102A
  21. EP260101a: Global MASTER-Net observations report
  22. GRB 260102A: SVOM detection of a burst
  23. Fermi GRB 251228A: Global MASTER-Net observations report
  24. SVOM GRB251227.07: Global MASTER-Net observations report
  25. IceCube Alert 251225.84: Global MASTER-Net observations report
  26. EP251222a: NTT/ULTRACAM optical observations
  27. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  28. EP251221a: NOT optical upper limit
  29. IceCube-251218A: COLIBRÍ optical upper limits
  30. Fermi GRB 251215A: Global MASTER-Net observations report
  31. GRB 251203B: AbAO optical observations
  32. GRB 251214B: COLIBRÍ observations of the afterglow
  33. GRB 251214B: SVOM/C-GFT optical observations
  34. GRB 251214B: Swift detection of a burst with an optical counterpart
  35. EP251212a: Global MASTER-Net observations report
  36. GRB 251209A: NuSTAR detection of prompt emission
  37. EP251130a: Mondy and AbAO optical observations
  38. GRB 251209A: Fermi GBM Final Real-time Localization
  39. GRB 251208D: Swift-XRT observations
  40. GRB 251129A: e-MERLIN C-band observations
  41. LAT GRB251208.43: Global MASTER-Net observations report
  42. GRB 251205A: Liverpool Telescope further optical follow-up observations
  43. SVOM GRB251208D: Global MASTER-Net observations report
  44. GRB 251203A: AstroSat CZTI detection
  45. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  46. GRB 251203C: SVOM/VT optical counterpart
  47. GRB 251203C: EP-FXT follow-up observation
  48. GRB 251203B: Swift-XRT observations
  49. GRB 251203C: LCO optical upper limits
  50. GRB 251203B: LCO optical upper limits
  51. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  52. SVOM GRB251203.77: Global MASTER-Net observations report
  53. SVOM GRB251203B: Global MASTER-Net observations report
  54. GRB 251203A: Fermi GBM Final Real-time Localization
  55. GRB 251202B: Fermi GBM Final Real-time Localization
  56. GRB 251202A: GOTO optical afterglow detection
  57. EP251130a: SAO RAS optical observations
  58. GRB 251201A: MAXI/GSC detection
  59. GRB 251129A / EP251129a: SVOM/VT optical fading
  60. EP251129a: Global MASTER-Net observations report
  61. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  62. SVOM GRB251129A: Global MASTER-Net observations report
  63. GRB 251127A: Glowbug gamma-ray detection
  64. Fermi GRB 251127A: Global MASTER-Net observations report
  65. GRB 251127A: Fermi GBM Final Real-time Localization
  66. Fermi GRB 251125A: Global MASTER-Net observations report
  67. GRB 251124A: Fermi GBM Localization by automated pipeline
  68. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  69. GRB 251115A: Fermi GBM Observation
  70. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  71. GRB 251018A: FRAM-Auger optical detection
  72. EP251118a: GOTO optical afterglow detection
  73. EP251118a: Global MASTER-Net observations report
  74. LAT GRB251118.86: Global MASTER-Net observations report
  75. EP251118a: NOT candidate optical counterpart
  76. SVOM GRB251116C: Global MASTER-Net observations report
  77. GRB 251115A: Fermi-LAT detection
  78. Fermi GRB 251115A: Global MASTER-Net observations report
  79. GRB 251115A: Fermi GBM Final Real-time Localization
  80. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  81. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  82. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  83. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  84. GRB 251108B: Glowbug gamma-ray detection
  85. GRB 251111A: Swift-XRT afterglow detection
  86. GRB 251013C: Chandra X-ray observations and jet break detection
  87. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  88. Fermi trigger No 784279167: Global MASTER-Net observations report
  89. SVOM GRB251108.54: Global MASTER-Net observations report
  90. SVOM GRB251106.83: Global MASTER-Net observations report
  91. GRB 251106A: MASTER optical observations
  92. GRB 251103B: AstroSat CZTI detection
  93. GRB 251103B: Fermi GBM observation
  94. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  95. EP251102a: OHP/T193 optical observations
  96. GRB 251103A: OHP/T193 optical observations
  97. GRB 251103A: Xinglong 2.16m optical detection
  98. GRB 251103B: Nanshan/HMT optical upper limit
  99. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  100. GRB 251103B: MITSuME Akeno optical upper limits

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