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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"

5390 results found.

  1. GRB 251103B: MITSuME Akeno optical upper limits
  2. Fermi GRB 251103A: Global MASTER-Net observations report
  3. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  4. Swift GRB 251103B: Global MASTER-Net observations report
  5. GRB 251103B: GROWTH-India Telescope optical upper limits
  6. GRB 251103B: Prompt enhanced Swift-XRT position
  7. GRB 251103A: Fermi GBM Observation
  8. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  9. GRB 251103A: LCO optical observation
  10. EP251102.890: COLIBRÍ optical counterpart candidate
  11. GRB 251102A: AstroSat CZTI detection
  12. GRB 251103A: Fermi GBM Final Localization
  13. GRB 251103A: NOT optical afterglow candidate
  14. GRB 251102A: Fermi GBM Final Real-time Localization
  15. Konus-Wind detection of GRB 251028A
  16. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  17. GRB 251028A: Fermi GBM Observation
  18. GRB 251028A: Glowbug gamma-ray detection
  19. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  20. GRB 251028A: MAXI/GSC detection
  21. GRB 251028A: Fermi GBM Final Real-time Localization
  22. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  23. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  24. GRB 251026B: Tentative GOTO optical counterpart candidate
  25. Fermi GRB 251025C: Global MASTER-Net observations report
  26. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  27. EP251023a: OHP/T193 optical observations
  28. GRB 251022A: Swift-XRT detection of GOTO25iym
  29. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  30. GRB 251022A: MASTER OT detection
  31. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  32. Fermi GRB 251023A: Global MASTER-Net observations report
  33. GRB 251022A: GOTO optical counterpart detection
  34. LAT GRB251022A: Global MASTER-Net observations report
  35. EP251021b: BOOTES-7 optical upper limit
  36. GRB 250911A: MAXI/GSC detection
  37. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  38. IceCube-251018A: DDOTI Optical Upper Limit
  39. GRB 251018A: Fermi GBM Observation
  40. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  41. IceCube-251018A: Global MASTER-Net observations report
  42. GRB 251017A: COLIBRÍ photometric redshift
  43. GRB 251018A: MASTER OT detection
  44. GRB 251018A: TRT optical afterglow detection
  45. Swift GRB 251018A: Global MASTER-Net observations report
  46. GRB 251018A: Swift detection of a burst with an optical counterpart
  47. GRB 251018A: Fermi GBM Final Real-time Localization
  48. GRB 251011A: Fermi GBM Observation
  49. GRB 251013C: Leavitt Observatory optical photometry
  50. Fermi GRB 251016B: Global MASTER-Net observations report
  51. GRB 251017A: Swift detection of a burst with an optical counterpart
  52. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  53. GRB 251013C: VLA detection
  54. GRB 251013D: Swift/UVOT Observations
  55. GRB 251013C: Swift/UVOT Detection
  56. GRB 251014D: BOOTES-6/DPRT optical upper limit
  57. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  58. GRB 251013C: Bassano Bresciano Observatory optical observations
  59. GRB 251013C: ABObservatory optical observations
  60. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  61. GRB 251013C: ALMA detection
  62. GRB 251013C: DDOTI detection of the optical afterglow
  63. GRB 251013C: SLKT optical afterglow photometry
  64. GRB 251013C: Swift-XRT counterpart detection
  65. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  66. GRB 251011B inspection: MASTER orphan GRB detection
  67. GRB 251011A: AstroSat CZTI detection
  68. GRB 251011A: Fermi GBM Final Real-time Localization
  69. GRB 251003A: Fermi GBM Observation
  70. GRB 251007A: AKO Optical Upper Limit
  71. EP251003a: LCO and VST fading optical counterpart
  72. Fermi GRB 251006B: Global MASTER-Net observations report
  73. GRB 251003A: LAST optical observations
  74. GRB 251002A: Mondy/AZT-33IK optical observations
  75. GRB 251002A: NIR observations with WINTER
  76. Fermi GBM Sub-Threshold Detection of GRB 250910A
  77. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  78. GRB 251003A: COLIBRÍ photometric redshift
  79. GRB 251003A: GOTO detection of the optical counterpart
  80. GRB 251002A: GOTO detection of optical counterpart
  81. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  82. GRB 251002A: AbAO optical observations
  83. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  84. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  85. GRB 251003A: LCOGT Optical Detection
  86. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  87. Swift GRB251003A: Global MASTER-Net observations report
  88. GRB 251001B: SVOM/VT optical observation
  89. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  90. GRB 250925A/EP250925a: EP-WXT detection
  91. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  92. GRB 250924A: Swift/UVOT Detection
  93. GRB 250924A: COLIBRÍ optical observations
  94. GRB 250924A: Swift detection of a burst with an optical counterpart
  95. Fermi GRB 250922B: Global MASTER-Net observations report
  96. Fermi trigger No 780156732: Global MASTER-Net observations report
  97. GRB 250922A: Fermi GBM Final Localization
  98. GRB 250920B: Enhanced Swift-XRT position
  99. GRB 250920C: GOTO optical counterpart candidate
  100. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time

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