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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"

24167 results found.

  1. GRB 250628B: Swift-XRT observations
  2. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  3. GRB 250628B: EP-FXT counterpart detection
  4. GRB 250627A: SVOM/GRM detection of a short burst
  5. GRB 250628A: REM optical/NIR upper limits
  6. GRB 250628C: Fermi GBM Final Real-time Localization
  7. GRB 250628B: SVOM detection of a long burst
  8. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  9. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  10. GRB 250628A: VLT/X-shooter upper limits
  11. GRB 250628A: Swift/UVOT Upper Limits
  12. GRB 250628A: Swift-XRT refined Analysis
  13. Fermi GRB 250626A: Global MASTER-Net observations report
  14. Swift GRB 250628A: Global MASTER-Net observations report
  15. GRB 250628A: Swift detection of a burst
  16. GRB 250625A: Swift-BAT refined analysis
  17. GRB 250625A: Leavitt Observatory afterglow detection
  18. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  19. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  20. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  21. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  22. GRB 250626A: Fermi GBM Final Real-time Localization
  23. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  24. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  25. GRB 250625A: SVOM/C-GFT upper limit in early phase
  26. GRB 250625A: GECAM-B detection
  27. GRB 250625A: Swift/UVOT Upper Limits
  28. GRB 250625A: ABObservatory afterglow detection
  29. GRB 250625A: OHP/T193 optical detection
  30. GRB 250625A: COLIBRÍ optical observations
  31. GRB 250625A: Fermi-LAT detection
  32. GRB 250625A: Swift-XRT refined Analysis
  33. GRB 250625A: JinShan optical observations
  34. GRB250625A: Fermi GBM Observation
  35. Swift GRB 250625A: Global MASTER-Net observations report
  36. GRB 250625A: NOT z-band upper limit
  37. GRB 250625A: SVOM/VT optical confirmation
  38. GRB 250620B: Fermi GBM Observation
  39. Fermi GRB 250625A: Global MASTER-Net observations report
  40. GRB 250625A: Swift detection of a burst
  41. GRB 250625A: Fermi GBM Final Real-time Localization
  42. GRB 250620A: AstroSat CZTI detection
  43. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  44. Fermi GRB 250624A: Global MASTER-Net observations report
  45. GRB 250624A: Fermi GBM Final Real-time Localization
  46. Fermi GRB 250623A: Global MASTER-Net observations report
  47. GRB 250623A: Fermi GBM Final Real-time Localization
  48. GRB 250521A: VZLUSAT-2 detection
  49. GRB 250617B: Swift-BAT refined analysis
  50. Fermi trigger No 772190032: Global MASTER-Net observations report
  51. IPN triangulation of GRB 250620С (long/bright)
  52. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  53. GRB 250620C: SVOM/GRM observation
  54. GRB 250620A: SVOM/GRM observation of a short burst
  55. GRB250620A: Fermi GBM Observation
  56. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  57. Fermi GRB 250621A: Global MASTER-Net observations report
  58. GRB 250619B: Fermi GBM Observation
  59. GRB 250621A: Fermi GBM Final Real-time Localization
  60. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  61. GRB250620C: Fermi GBM Observation
  62. The EP-WXT trigger 01709179071 is likely a flaring star
  63. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  64. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  65. GRB 250620C: Fermi GBM Final Real-time Localization
  66. Fermi trigger No 772128434: Global MASTER-Net observations report
  67. GRB 250620B: Fermi GBM Final Real-time Localization
  68. GRB 250620A: Fermi GBM Final Real-time Localization
  69. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  70. GRB 250619B: Fermi GBM Final Real-time Localization
  71. Fermi trigger No 772058337: Global MASTER-Net observations report
  72. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  73. GRB 250615A: Kilonova-Catcher optical upper limits
  74. GRB 250619A: Fermi GBM Final Real-time Localization
  75. GRB 250617B: Assy AZT-20 Optical Observations
  76. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  77. Fermi GRB 250617A: Global MASTER-Net observations report
  78. GRB 250615A/EP250615a: FTW optical and NIR observations
  79. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  80. GRB 250617B: Swift/UVOT Detection
  81. GRB 250617B: Kilonova-Catcher optical afterglow detection
  82. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  83. GRB 250617B: COLIBRÍ optical observations
  84. GRB 250617B: NOT NIR observations of the afterglow
  85. GRB 250617B: Swift-XRT refined Analysis
  86. GRB 250617B: SVOM/VT optical observation
  87. GRB 250617B: NUTTelA-TAO early time optical observations
  88. Fermi trigger No 771886893: Global MASTER-Net observations report
  89. Swift GRB 250617B: Global MASTER-Net observations report
  90. GRB 250617B: GOTO optical upper limit
  91. GRB 250617B: Fermi GBM Observation
  92. GRB 250615A: Swift-BAT refined analysis
  93. The EP-WXT trigger 01709178990 is likely a flaring star
  94. GRB 250617B: Fermi GBM Final Localization
  95. GRB 250617B: Ondrejov D50 optical afterglow detection
  96. GRB 250617B: SAO RAS optical observations
  97. GRB 250617B: Swift detection of a burst with an optical counterpart
  98. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  99. GRB 250617A: Fermi GBM Final Real-time Localization
  100. IPN triangulation of GRB 250612C (short/hard)

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