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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"

5059 results found.

  1. Fermi GRB 251023A: Global MASTER-Net observations report
  2. GRB 251022A: GOTO optical counterpart detection
  3. LAT GRB251022A: Global MASTER-Net observations report
  4. EP251021b: BOOTES-7 optical upper limit
  5. GRB 250911A: MAXI/GSC detection
  6. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  7. IceCube-251018A: DDOTI Optical Upper Limit
  8. GRB 251018A: Fermi GBM Observation
  9. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  10. IceCube-251018A: Global MASTER-Net observations report
  11. GRB 251017A: COLIBRÍ photometric redshift
  12. GRB 251018A: MASTER OT detection
  13. GRB 251018A: TRT optical afterglow detection
  14. Swift GRB 251018A: Global MASTER-Net observations report
  15. GRB 251018A: Swift detection of a burst with an optical counterpart
  16. GRB 251018A: Fermi GBM Final Real-time Localization
  17. GRB 251011A: Fermi GBM Observation
  18. GRB 251013C: Leavitt Observatory optical photometry
  19. Fermi GRB 251016B: Global MASTER-Net observations report
  20. GRB 251017A: Swift detection of a burst with an optical counterpart
  21. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  22. GRB 251013C: VLA detection
  23. GRB 251013D: Swift/UVOT Observations
  24. GRB 251013C: Swift/UVOT Detection
  25. GRB 251014D: BOOTES-6/DPRT optical upper limit
  26. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  27. GRB 251013C: Bassano Bresciano Observatory optical observations
  28. GRB 251013C: ABObservatory optical observations
  29. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  30. GRB 251013C: ALMA detection
  31. GRB 251013C: DDOTI detection of the optical afterglow
  32. GRB 251013C: SLKT optical afterglow photometry
  33. GRB 251013C: Swift-XRT counterpart detection
  34. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  35. GRB 251011B inspection: MASTER orphan GRB detection
  36. GRB 251011A: AstroSat CZTI detection
  37. GRB 251011A: Fermi GBM Final Real-time Localization
  38. GRB 251003A: Fermi GBM Observation
  39. GRB 251007A: AKO Optical Upper Limit
  40. EP251003a: LCO and VST fading optical counterpart
  41. Fermi GRB 251006B: Global MASTER-Net observations report
  42. GRB 251003A: LAST optical observations
  43. GRB 251002A: Mondy/AZT-33IK optical observations
  44. GRB 251002A: NIR observations with WINTER
  45. Fermi GBM Sub-Threshold Detection of GRB 250910A
  46. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  47. GRB 251003A: COLIBRÍ photometric redshift
  48. GRB 251003A: GOTO detection of the optical counterpart
  49. GRB 251002A: GOTO detection of optical counterpart
  50. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  51. GRB 251002A: AbAO optical observations
  52. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  53. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  54. GRB 251003A: LCOGT Optical Detection
  55. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  56. Swift GRB251003A: Global MASTER-Net observations report
  57. GRB 251001B: SVOM/VT optical observation
  58. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  59. GRB 250925A/EP250925a: EP-WXT detection
  60. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  61. GRB 250924A: Swift/UVOT Detection
  62. GRB 250924A: COLIBRÍ optical observations
  63. GRB 250924A: Swift detection of a burst with an optical counterpart
  64. Fermi GRB 250922B: Global MASTER-Net observations report
  65. Fermi trigger No 780156732: Global MASTER-Net observations report
  66. GRB 250922A: Fermi GBM Final Localization
  67. GRB 250920B: Enhanced Swift-XRT position
  68. GRB 250920C: GOTO optical counterpart candidate
  69. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  70. EP250919a: Global MASTER-Net observations report
  71. EP250916a: EP-FXT follow-up observation
  72. GRB 250916A: GOTO optical counterpart candidate
  73. GRB250912A: VLT/HAWK-I follow-up observations
  74. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP250910a: Global MASTER-Net observations report
  76. GRB 250910A: LCO optical upper limit
  77. EP250908c: Global MASTER-Net observations report
  78. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  79. EP250905a: Liverpool Telescope i-band upper limits
  80. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  81. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  82. IceCube Alert 250905.84: Global MASTER-Net observations report
  83. GRB 250905A: KAIT optical upper limit
  84. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  85. GRB 250904A: Prompt enhanced Swift-XRT position
  86. GRB 250904A: Swift detection of a burst
  87. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  88. GRB 250903A: LCO optical observation
  89. GRB 250903A: LCO optical afterglow detection
  90. EP250903a: LCO candidate counterpart discovery
  91. GRB 250903A: TRT optical counterpart detection
  92. EP250903a: Global MASTER-Net observations report
  93. EP250903a: TRT optical observations
  94. EP250903a: Einstein Probe detection of an X-ray transient
  95. EP 250827B: Detection of supernova counterpart by LCO.
  96. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  97. EP250827b: continued Liverpool Telescope observations
  98. Fermi GRB 250902B: Global MASTER-Net observations report
  99. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  100. GRB 250901A: EP-FXT follow-up observation

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