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"

39039 results found.

  1. GRB 250625A: Enhanced Swift-XRT position
  2. Fermi GRB 250625A: Global MASTER-Net observations report
  3. GRB 250625A: Swift detection of a burst
  4. GRB 250625A: Fermi GBM Final Real-time Localization
  5. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  6. GRB 250620A: AstroSat CZTI detection
  7. GRB 241018A: Maidanak optical observations
  8. GRB 250620C: AstroSat CZTI detection
  9. Fermi GRB 250624A: Global MASTER-Net observations report
  10. GRB 250624A: Fermi GBM Final Real-time Localization
  11. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  12. Fermi GRB 250623A: Global MASTER-Net observations report
  13. GRB 250623A: Fermi GBM Final Real-time Localization
  14. GRB 250521A: VZLUSAT-2 detection
  15. GRB 250617B: Swift-BAT refined analysis
  16. Fermi trigger No 772190032: Global MASTER-Net observations report
  17. Konus-Wind detection of GRB 250620C
  18. IPN triangulation of GRB 250620C (long/bright)
  19. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  20. GRB 250620C: SVOM/GRM observation
  21. GRB 250620A: SVOM/GRM observation of a short burst
  22. GRB250620A: Fermi GBM Observation
  23. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  24. Fermi GRB 250621A: Global MASTER-Net observations report
  25. GRB 250619B: Fermi GBM Observation
  26. GRB 250621A: Fermi GBM Final Real-time Localization
  27. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  28. GRB250620C: Fermi GBM Observation
  29. GRB 250506A - SVOM/ECLAIRs Refined analysis
  30. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  31. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  32. GRB 250620C: Fermi GBM Final Real-time Localization
  33. Fermi trigger No 772128434: Global MASTER-Net observations report
  34. GRB 250620B: Fermi GBM Final Real-time Localization
  35. GRB 250620A: Fermi GBM Final Real-time Localization
  36. GRB 250617B: Nickel telescope optical observations
  37. GRB 250619B: Fermi GBM Final Real-time Localization
  38. Fermi trigger No 772058337: Global MASTER-Net observations report
  39. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  40. GRB 250615A: Kilonova-Catcher optical upper limits
  41. GRB 250619A: Fermi GBM Final Real-time Localization
  42. GRB 250617B: Assy AZT-20 Optical Observations
  43. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  44. Fermi GRB 250617A: Global MASTER-Net observations report
  45. GRB 250615A/EP250615a: FTW optical and NIR observations
  46. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  47. GRB 250617B: Swift/UVOT Detection
  48. GRB 250617B: Kilonova-Catcher optical afterglow detection
  49. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  50. GRB 250617B: COLIBRÍ optical observations
  51. GRB 250617B: NOT NIR observations of the afterglow
  52. GRB 250617B: Swift-XRT refined Analysis
  53. GRB 250617B: SVOM/VT optical observation
  54. GRB 250617B: NUTTelA-TAO early time optical observations
  55. Fermi trigger No 771886893: Global MASTER-Net observations report
  56. Swift GRB 250617B: Global MASTER-Net observations report
  57. GRB 250617B: GOTO optical upper limit
  58. GRB 250617B: Enhanced Swift-XRT position
  59. GRB 250617B: Fermi GBM Observation
  60. GRB 250615A: Swift-BAT refined analysis
  61. GRB 250617B: Fermi GBM Final Localization
  62. GRB 250617B: Ondrejov D50 optical afterglow detection
  63. GRB 250617B: SAO RAS optical observations
  64. GRB 250617B: Swift detection of a burst with an optical counterpart
  65. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  66. GRB 250617A: Fermi GBM Final Real-time Localization
  67. IPN triangulation of GRB 250612C (short/hard)
  68. Konus-Wind detection of GRB 250615A / EP250615a
  69. GRB 250615A / EP250615a: AstroSat CZTI detection
  70. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  71. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  72. GRB 250615A: COLIBRÍ optical upper limit
  73. GRB 250615A: DDOTI Optical Upper Limit
  74. GRB 250615A: Swift/UVOT Upper Limits
  75. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  76. GRB 250615A: Swift-XRT refined Analysis
  77. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  78. Fermi trigger No 771752663: Global MASTER-Net observations report
  79. GRB 250615A: Enhanced Swift-XRT position
  80. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  81. GRB 250615A: Prompt enhanced Swift-XRT position
  82. GRB 250615A: Swift detection of a burst
  83. Swift GRB 250615A: Global MASTER-Net observations report
  84. Fermi trigger No 771718064: Global MASTER-Net observations report
  85. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  86. GRID detection of GRB 250612C
  87. sb25061207: Mephisto optical upper limits
  88. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  89. GRB 250614A: Fermi GBM Final Real-time Localization
  90. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  91. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  92. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  93. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  94. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. Fermi trigger No 771494087: Global MASTER-Net observations report
  96. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  97. GRB 250612B: Fermi GBM Observation
  98. Fermi trigger No 771424081: Global MASTER-Net observations report
  99. EP250612a: Global MASTER-Net observations report
  100. GRB 250612C: Fermi GBM Observation

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov