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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"

26038 results found.

  1. GRB 251011B: Swift/UVOT Upper Limits
  2. GRB 251011B: SVOM/GRM observation
  3. GRB 251011B: Swift-XRT refined Analysis
  4. GRB 251011B: Fermi GBM Observation
  5. GRB 251011B : MASTER optical observations
  6. GRB 251011B: Enhanced Swift-XRT position
  7. GRB 251011B: Swift detection of a burst
  8. GRB 251007B: Swift/UVOT Upper Limits
  9. GRB251007A: Swift/UVOT Detection
  10. GRB 251007A: Swift-BAT refined analysis
  11. GRB 251007A: SVOM/GRM observation
  12. GRB 251007A: Insight-HXMT detection
  13. GRB 251006A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 251006A: Fermi GBM Observation
  15. GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
  16. GRB 251003A: Fermi GBM Observation
  17. GRB 251007B: COLIBRÍ optical upper limit
  18. GRB 251007A: AstroSat CZTI detection
  19. GRB 251006B/EP251006a: EP-FXT afterglow detection
  20. GRB 250917B: iTelescope T-26 upper limit
  21. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  22. GRB 251007B: SVOM/VT optical candidate
  23. GRB 251007A: Swift-XRT refined Analysis
  24. GRB 251007A: Enhanced Swift-XRT position
  25. GRB 251007B: Swift-XRT refined Analysis
  26. GRB 251007B: Enhanced Swift-XRT position
  27. GRB 251007A: NOT optical observations
  28. GRB 251007A: AKO Optical Upper Limit
  29. GRB 251007A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 251007A: SVOM/C-GFT optical observations
  31. GRB 251005C: PRIME J-band upper limit
  32. Swift GRB 251007B: Global MASTER-Net observations report
  33. GRB 251007A: Glowbug gamma-ray detection
  34. GRB 251007B: SVOM/C-GFT upper limit
  35. Swift GRB 251007A: Global MASTER-Net observations report
  36. GRB 251007B: SVOM detection of a faint burst
  37. GRB 251007B: Swift detection of a burst
  38. GRB 251007A: Swift detection of a burst with an optical counterpart
  39. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  40. GRB 251005C: SVOM/GRM observation of a likely short GRB
  41. GRB 251005C: COLIBRÍ optical observations
  42. GRB 251005C: VLT/X-shooter Imaging
  43. GRB 251003A: LAST optical observations
  44. GRB 251005C: SVOM/VT optical candidate
  45. GRB 251005C: AstroSat CZTI detection
  46. GRB 251005C: Swift/UVOT Upper Limits
  47. GRB 251005C: Swift-XRT refined Analysis
  48. GRB 251005C: Fermi GBM Observation
  49. Swift GRB 251005A: Global MASTER-Net observations report
  50. GRB 251005C: Enhanced Swift-XRT position
  51. GRB 251005C: GOTO optical upper limits
  52. GRB 251005C: Swift detection of a burst
  53. Fermi GBM Sub-Threshold Detection of GRB 250910A
  54. GRB 251003A: Swift-BAT refined analysis
  55. GRB 251003A: Swift/UVOT Upper Limits
  56. GRB 251002A: Swift/UVOT detection
  57. GRB 251003A: Swift-XRT refined Analysis
  58. GRB 251003A: COLIBRÍ photometric redshift
  59. GRB 251003A: Enhanced Swift-XRT position
  60. GRB 251002A: AKO Early Optical Afterglow Detection
  61. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  62. GRB 251003A: Kilonova-Catcher optical afterglow detection
  63. GRB 251002A: Swift-XRT afterglow detection
  64. GRB 251001B: AbAO optical upper limit
  65. GRB 251002A: Kilonova-Catcher optical afterglow detection
  66. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  67. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  68. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  69. GRB 251003A: LCOGT Optical Detection
  70. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  71. GRB 251003A: 1.5m OSN afterglow candidate
  72. GRB 251003A: Prompt enhanced Swift-XRT position
  73. GRB 251003A: Swift detection of a burst
  74. Swift GRB251003A: Global MASTER-Net observations report
  75. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  76. GRB 251002A: FRAM-ORM afterglow detection
  77. GRB 251001B: Swift-BAT refined analysis
  78. GRB 251001B: Swift/UVOT Detection
  79. GRB 251001B: COLIBRÍ optical observations
  80. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  81. GRB 251001B: Swift-XRT refined Analysis
  82. GRB 251001B: SVOM/VT optical observation
  83. GRB 251001B: NOT optical observations
  84. Swift GRB 251001B: Global MASTER-Net observations report
  85. GRB 251001B: Fermi GBM Observation
  86. GRB 251001B: Enhanced Swift-XRT position
  87. GRB 251001B: LCOGT Optical Observations
  88. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  89. GRB 251001B: GOTO optical counterpart detection
  90. GRB 251001B: Swift detection of a burst
  91. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  92. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  93. GRB 250925A: MAO/AZT-22 optical observations
  94. GRB 250925A: Mondy I-band optical observations
  95. GRB 250924A: SVOM/GRM observation
  96. GRB 250925A: Swift-XRT refined Analysis
  97. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  98. GRB 250925A: Swift/UVOT Upper Limits
  99. GRB 250925A: Swift-BAT refined analysis
  100. GRB 250925A: Mondy and AbAO optical observations

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