Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! See news and announcements

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"

12320 results found.

  1. EP250508a: Liverpool Telescope optical upper limits
  2. EP250508a: KAIT optical upper limit
  3. GRB 250507A: KAIT optical upper limit
  4. EP250508a: Global MASTER-Net observations report
  5. GRB 250506A: SVOM/VT optical upper limit
  6. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  7. GRB 250506A: Swift/UVOT Upper Limits
  8. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  9. GRB 250507A: SVOM/VT optical upper limit
  10. GRB 250506A: Swift-XRT observations
  11. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  12. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  13. GRB 250506A: Mephisto optical upper limits
  14. GRB 250502A: Bassano Bresciano Observatory upper limit
  15. IceCube Alert 250506.59: Global MASTER-Net observations report
  16. GRB 250506A: Xinglong 2.16m optical upper limit
  17. SVOM/sb25050601: EP-FXT observations
  18. GRB 250506A: REM optical/NIR upper limits
  19. GRB 250506A: Swift XRT observations and possible counterpart detection
  20. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  21. GRB 250504A: VLT/X-shooter upper limits
  22. Fermi GRB 250505A: Global MASTER-Net observations report
  23. GRB 250504A: SVOM/VT upper limit
  24. Fermi GRB 250504A: Global MASTER-Net observations report
  25. GRB 250504A: Swift detection of a burst
  26. Swift GRB250504.98: Global MASTER-Net observations report
  27. Fermi trigger No 767975731: Global MASTER-Net observations report
  28. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  29. GRB 250430A: Swift/UVOT Detection
  30. Fermi GRB 250502B: Global MASTER-Net observations report
  31. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  32. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  33. GRB 250430A / EP250430a: J-band upper limits with WINTER
  34. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  35. GRB 250430A: Leavitt Observatory optical upper limit
  36. GRB 250430A: Bassano Bresciano Observatory upper limit
  37. GRB 250430A : MITSuME Akeno optical upper limits
  38. SVOM/sb25043004: EP-FXT observations
  39. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  40. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 250430A: Kanata optical upper limit
  42. Swift GRB250430.73: Global MASTER-Net observations report
  43. EP250428b: FTW optical and NIR observations
  44. Fermi trigger No 767623859: Global MASTER-Net observations report
  45. EP250428b: GROWTH-India telescope optical upper limit
  46. EP250428b: SVOM/VT upper limit
  47. EP250428b: SAO RAS optical upper limit
  48. EP250428b: LAST optical upper limit
  49. GRB 250427A: Swift/UVOT Detection
  50. EP250428b: Global MASTER-Net observations report
  51. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  52. EP250427a: Global MASTER-Net observations report
  53. IceCube Alert 250426.74: Global MASTER-Net observations report
  54. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  55. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 250424A: Swift/UVOT Detection
  57. Fermi-LAT gamma-ray observations of IceCube-250421A
  58. GRB 250419a: Continued Liverpool Telescope observations
  59. GRB 250419A: Liverpool Telescope optical upper limit
  60. Swift GRB 250424A: Global MASTER-Net observations report
  61. Swift GRB 250424A: Global MASTER-Net OT detection
  62. EP250421a: Nickel optical upper limit
  63. EP250421a: Upper limits from Fermi-GBM Observations
  64. SVOM/sb25042207: XRT observations
  65. SVOM/sb25042207: BOOTES-2 early optical upper limit
  66. SVOM/sb25042207: GOTO optical upper limits
  67. GRB 250419A: Mephisto Multi-band Optical Detection
  68. EP250421a: REM optical upper limit
  69. EP250421A: COLIBRÍ Optical Upper Limit
  70. Fermi GRB 250421A: Global MASTER-Net observations report
  71. EP250421a: Global MASTER-Net observations report
  72. IceCube Alert 250421.71: Global MASTER-Net observations report
  73. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  74. GRB 250419A: MASTER optical afterglow observation
  75. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  76. GRB 250419A: GOTO optical counterpart detection
  77. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  78. EP250416a: GSP optical upper limit
  79. EP250416a: Global MASTER-Net observations report
  80. IceCube-250416A: Global MASTER-Net observations report
  81. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  82. EP250304a: ATCA radio observations
  83. Fermi trigger No 766148493: Global MASTER-Net observations report
  84. Fermi trigger No 766173972: Global MASTER-Net observations report
  85. Fermi GRB 250411A: Global MASTER-Net observations report
  86. GRB 250314A: e-MERLIN observations
  87. EP250227a: Further NOT optical observations
  88. EP250407a: Global MASTER-Net observations report
  89. Fermi-LAT gamma-ray observations of IceCube-250406A
  90. EP250407a: Swift-XRT observations
  91. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  92. GRB 250407A: Swift-XRT afterglow detection
  93. Fermi GRB 250407A: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  95. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  96. Konus-Wind detection of GRB 250406B (short/hard)
  97. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  98. IceCube Alert 250406.95: Global MASTER-Net observations report
  99. Fermi trigger No 765663719: Global MASTER-Net observations report
  100. Fermi GRB 250406A: Global MASTER-Net observations report

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Looking for U.S. government information and services? Visit USA.gov