Skip to main content
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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"
  1. GRB 250620C: Fermi GBM Final Real-time Localization
  2. Fermi trigger No 772128434: Global MASTER-Net observations report
  3. GRB 250620B: Fermi GBM Final Real-time Localization
  4. GRB 250620A: Fermi GBM Final Real-time Localization
  5. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  6. GRB 250617B: Nickel telescope optical observations
  7. GRB 250619B: Fermi GBM Final Real-time Localization
  8. Fermi trigger No 772058337: Global MASTER-Net observations report
  9. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  10. GRB 250615A: Kilonova-Catcher optical upper limits
  11. GRB 250619A: Fermi GBM Final Real-time Localization
  12. GRB 250617B: Assy AZT-20 Optical Observations
  13. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  14. Fermi GRB 250617A: Global MASTER-Net observations report
  15. GRB 250615A/EP250615a: FTW optical and NIR observations
  16. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  17. GRB 250617B: Swift/UVOT Detection
  18. GRB 250617B: Kilonova-Catcher optical afterglow detection
  19. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  20. GRB 250617B: COLIBRÍ optical observations
  21. GRB 250617B: NOT NIR observations of the afterglow
  22. GRB 250617B: Swift-XRT refined Analysis
  23. GRB 250617B: SVOM/VT optical observation
  24. GRB 250617B: NUTTelA-TAO early time optical observations
  25. Fermi trigger No 771886893: Global MASTER-Net observations report
  26. Swift GRB 250617B: Global MASTER-Net observations report
  27. GRB 250617B: GOTO optical upper limit
  28. GRB 250617B: Enhanced Swift-XRT position
  29. GRB 250617B: Fermi GBM Observation
  30. GRB 250615A: Swift-BAT refined analysis
  31. The EP-WXT trigger 01709178990 is likely a flaring star
  32. GRB 250617B: Fermi GBM Final Localization
  33. GRB 250617B: Ondrejov D50 optical afterglow detection
  34. GRB 250617B: SAO RAS optical observations
  35. GRB 250617B: Swift detection of a burst with an optical counterpart
  36. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  37. GRB 250617A: Fermi GBM Final Real-time Localization
  38. IPN triangulation of GRB 250612C (short/hard)
  39. EP#01709178975: Swift-XRT counterpart detection
  40. EP-WXT trigger 01709178975: GOTO optical upper limit
  41. The EP-WXT trigger 01709178975 is likely a flaring star
  42. Konus-Wind detection of GRB 250615A / EP250615a
  43. GRB 250615A / EP250615a: AstroSat CZTI detection
  44. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  45. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  46. GRB 250615A: COLIBRÍ optical upper limit
  47. GRB 250615A: DDOTI Optical Upper Limit
  48. GRB 250615A: Swift/UVOT Upper Limits
  49. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  50. GRB 250615A: Swift-XRT refined Analysis
  51. sb25061207/SVOM: T120 OHP optical upper limit
  52. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  53. Fermi trigger No 771752663: Global MASTER-Net observations report
  54. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  55. The EP-WXT trigger 01709178875 is likely a flaring star
  56. GRB 250615A: Enhanced Swift-XRT position
  57. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  58. GRB 250615A: Prompt enhanced Swift-XRT position
  59. GRB 250615A: Swift detection of a burst
  60. Swift GRB 250615A: Global MASTER-Net observations report
  61. Fermi trigger No 771718064: Global MASTER-Net observations report
  62. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  63. GRID detection of GRB 250612C
  64. sb25061207: Mephisto optical upper limits
  65. IceCube alert 141029_8144692 retraction
  66. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  67. GRB 250614A: Fermi GBM Final Real-time Localization
  68. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  69. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  70. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  71. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  72. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. Fermi trigger No 771494087: Global MASTER-Net observations report
  74. sb25061218: Swift-XRT observations
  75. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  76. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  77. sb25061207: EP-FXT follow-up observation and afterglow candidate
  78. GRB 250612B: Fermi GBM Observation
  79. EP250612a: SVOM/VT optical candidate
  80. Fermi trigger No 771424081: Global MASTER-Net observations report
  81. EP250612a: Global MASTER-Net observations report
  82. GRB 250612C: Fermi GBM Observation
  83. sb25061218: SVOM detection of a X-ray transient
  84. sb25061207: Swift-XRT observations
  85. EP250612a/GRB 250612B: JinShan optical upper limit
  86. EP 250612a: AST3-3 Yaoan Optical Observation
  87. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  88. sb25061207: SVOM/VT optical counterpart
  89. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  90. GRB 250610B: Swift-XRT refined Analysis
  91. GRB 250612C: Fermi GBM Final Real-time Localization
  92. EP250610a: Upper limit from Fermi-GBM Observations
  93. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  94. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  95. EP250612a: Einstein Probe detection of an X-ray transient
  96. GRB 250610B: Liverpool Telescope continued monitoring
  97. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  98. sb25061207: SVOM detection of a X-ray transient
  99. EP250610a: continuous follow-up observations with EP-FXT
  100. GRB 250610B - SVOM/ECLAIRs refined analysis

Advanced

Download all Circulars as a .tar.gz archive:
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