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"

27039 results found.

  1. GRB 251001C: Glowbug gamma-ray detection
  2. Swift GRB 251001B: Global MASTER-Net observations report
  3. GRB 251001B: Fermi GBM Observation
  4. GRB 251001B: Further GOTO observations of optical counterpart.
  5. GRB 250930A: Fermi GBM Final Localization
  6. GRB 251001B: LCOGT Optical Observations
  7. GRB 250930A: SVOM/GRM observation
  8. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  9. GRB 251001B: GOTO optical counterpart detection
  10. GRB 251001B: Swift detection of a burst
  11. GRB 251001B: Fermi GBM Final Real-time Localization
  12. GRB 251001A: Fermi GBM Detection
  13. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  14. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  15. GRB 251001A: Fermi GBM Final Real-time Localization
  16. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  17. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  18. GRB 250925A: MAO/AZT-22 optical observations
  19. Fermi GRB 250929A: Global MASTER-Net observations report
  20. GRB 250929A: Fermi GBM Final Real-time Localization
  21. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  22. GRB 250925A: Mondy I-band optical observations
  23. GRB 250916A: SVOM/VT optical observation
  24. GRB 250924A: SVOM/GRM observation
  25. GRB 250925A: Swift-XRT refined Analysis
  26. GRB 250926A: Insight-HXMT detection
  27. GRB 250926B: Fermi GBM Final Localization
  28. Fermi trigger No 780609036: Global MASTER-Net observations report
  29. IceCube Alert 250926.52: Global MASTER-Net observations report
  30. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  31. GRB 250925A: Swift-BAT refined analysis
  32. GRB 250925A: Mondy and AbAO optical observations
  33. GRB 250925A: COLIBRÍ photometric redshift
  34. GRB 250925A/EP250925a: EP-WXT detection
  35. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  36. GRB 250925A : MITSuME Akeno optical upper limits
  37. GRB 250925A: JinShan optical observations
  38. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  39. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  40. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  41. Fermi GRB 250926A: Global MASTER-Net observations report
  42. GRB 250926A: Fermi GBM Final Real-time Localization
  43. GRB250925A: Liverpool Telescope optical observations
  44. GRB 250925A: NOT optical afterglow candidate
  45. GRB 250925A: Leavitt Observatory optical upper limit
  46. GRB 250924A: Swift-BAT refined analysis
  47. GRB 250925A: GROWTH-India Telescope Upper Limits
  48. GRB 250925A: Swift detection of a burst
  49. Swift GRB 250925A: Global MASTER-Net observations report
  50. GRB 250922A: SVOM/GRM observation
  51. GRB 250924A: 1.6m Mephisto optical upper limits
  52. GRB 250924A: NOT optical observations
  53. GRB 250924A: SVOM/VT optical observation
  54. GRB 250924A: Swift/UVOT Detection
  55. GRB 250924A: Swift-XRT refined Analysis
  56. GRB 250924A: J-band detection with WINTER
  57. GRB 250924A: GROWTH-India Telescope Upper Limits
  58. GRB 250924A: Kilonova-Catcher optical afterglow detection
  59. GRB 250920C: Kilonova-Catcher optical afterglow detection
  60. GRB 250922B: SVOM/GRM observation
  61. GRB 250920C: TRT optical observation
  62. GRB 250924B: Fermi GBM Final Localization
  63. GRB 250924A: COLIBRÍ optical observations
  64. Swift GRB 250924A: Global MASTER-Net observations report
  65. GRB 250919A / EP250919a: further LCO optical observation
  66. GRB 250924A: DDOTI Detection of the Optical Counterpart
  67. GRB 250924A: Swift detection of a burst with an optical counterpart
  68. GRB 250920B: AbAO optical upper limits
  69. GRB 250920C: VLT redshift confirmation z = 1.399
  70. EP250911a: e-MERLIN radio observations
  71. GRB 250920B: CrAO ZTSH optical observations
  72. GRB 250920C: COLIBRÍ optical observations
  73. Fermi GRB 250922B: Global MASTER-Net observations report
  74. GRB 250920C: NIR observations with WINTER
  75. GRB 250920B: NIR observations with WINTER
  76. Fermi trigger No 780156732: Global MASTER-Net observations report
  77. GRB 250922B: Fermi GBM Final Real-time Localization
  78. IPN triangulation of GRB 250920A (long/bright)
  79. GRB 250916A: Swift/UVOT Detection
  80. GRB 250920C: Swift-XRT refined Analysis
  81. GRB 250922A: Fermi GBM Final Localization
  82. GRB 250920B: Kitab-ISON optical upper limit
  83. GRB 250920C: SVOM/GRM observation
  84. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  85. GRB 250920C: GROWTH-India Telescope optical observations
  86. GRB 250920C: Swift-BAT refined analysis
  87. GRB 250920B: Swift-BAT refined analysis
  88. GRB 250916A: FTW optical and NIR observations of the counterpart
  89. GRB 250920C: Swift/UVOT Detection
  90. GRB 250920B: Fermi GBM Observation
  91. GRB 250920A: Fermi GBM Detection
  92. GRB 250920C: Fermi GBM Observation
  93. Swift GRB 250920C: Global MASTER-Net observations report
  94. GRB 250920B: Swift/UVOT Detection
  95. GRB 250920B: FTW optical and NIR observations of the counterpart
  96. GRB 250920C: Optical counterpart detection by LCO
  97. GRB 250920A: SVOM/GRM observation
  98. GRB250920C: LCOGT Optical Detection
  99. GRB 250920B: Swift-XRT refined Analysis
  100. GRB 250920B: SVOM/C-GFT optical observations

Advanced

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