Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

24941 results found.

  1. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  2. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  3. Fermi trigger No 772128434: Global MASTER-Net observations report
  4. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  5. GRB 250617B: Nickel telescope optical observations
  6. GRB 250615A: Kilonova-Catcher optical upper limits
  7. GRB 250617B: Assy AZT-20 Optical Observations
  8. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  9. Fermi GRB 250617A: Global MASTER-Net observations report
  10. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  11. GRB 250617B: Swift/UVOT Detection
  12. GRB 250617B: Kilonova-Catcher optical afterglow detection
  13. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  14. GRB 250617B: COLIBRÍ optical observations
  15. GRB 250617B: NOT NIR observations of the afterglow
  16. GRB 250617B: Swift-XRT refined Analysis
  17. GRB 250617B: NUTTelA-TAO early time optical observations
  18. GRB 250617B: Enhanced Swift-XRT position
  19. GRB 250617B: Fermi GBM Observation
  20. GRB 250615A: Swift-BAT refined analysis
  21. GRB 250617B: SAO RAS optical observations
  22. GRB 250617B: Swift detection of a burst with an optical counterpart
  23. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  24. EP#01709178975: Swift-XRT counterpart detection
  25. EP-WXT trigger 01709178975: GOTO optical upper limit
  26. GRB 250615A / EP250615a: AstroSat CZTI detection
  27. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  28. GRB 250615A: COLIBRÍ optical upper limit
  29. GRB 250615A: DDOTI Optical Upper Limit
  30. GRB 250615A: Swift/UVOT Upper Limits
  31. GRB 250615A: Swift-XRT refined Analysis
  32. sb25061207/SVOM: T120 OHP optical upper limit
  33. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  34. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  35. GRB 250615A: Enhanced Swift-XRT position
  36. GRB 250615A: Swift detection of a burst
  37. Fermi trigger No 771718064: Global MASTER-Net observations report
  38. sb25061207: Mephisto optical upper limits
  39. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  40. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  41. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. sb25061218: Swift-XRT observations
  43. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  44. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  45. sb25061207: EP-FXT follow-up observation and afterglow candidate
  46. GRB 250612B: Fermi GBM Observation
  47. EP250612a: SVOM/VT optical candidate
  48. GRB 250612C: Fermi GBM Observation
  49. sb25061218: SVOM detection of a X-ray transient
  50. sb25061207: Swift-XRT observations
  51. EP250612a/GRB 250612B: JinShan optical upper limit
  52. sb25061207: SVOM/VT optical counterpart
  53. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  54. GRB 250610B: Swift-XRT refined Analysis
  55. EP250610a: Upper limit from Fermi-GBM Observations
  56. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  57. EP250612a: Einstein Probe detection of an X-ray transient
  58. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  59. sb25061207: SVOM detection of a X-ray transient
  60. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  61. Fermi GBM Sub-Threshold Detection of GRB 250610B
  62. GRB 250610B: Swift/UVOT Detection
  63. EP250610A: Swift/UVOT Upper limits
  64. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  65. EP250610a: TNG NIR upper limit
  66. GRB 250610B: REM optical/NIR observations
  67. EP250610a: Liverpool Telescope optical upper limits
  68. GRB 250610B: additional Liverpool Telescope optical observations
  69. GRB 250610B: SVOM/GRM analysis
  70. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  71. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  72. GRB 250610B: Swift-XRT counterpart detection
  73. GRB 250610B: SVOM/VT optical counterpart
  74. GRB 250610B: OHP/T120 optical counterpart candidate
  75. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  76. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  77. GRB 250605A: Swift-BAT refined analysis
  78. EP250610a: SVOM/VT optical upper limit
  79. EP250610a: REM optical/NIR observations
  80. GRB 250609A: Fermi GBM Observation
  81. EP250610a: Swift-XRT counterpart detection
  82. EP250610a: COLIBRÍ optical upper limit
  83. EP250610a: Einstein Probe detection of an X-ray transient
  84. Fermi trigger No 771072240: Global MASTER-Net observations report
  85. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  86. GRB 250605A: Swift/UVOT Upper Limits
  87. GRB 250527C: CrAO Optical Upper Limit
  88. GRB 250607A: SVOM/GRM observation of a long burst
  89. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  90. GRB 250605A: Swift-XRT refined Analysis
  91. GRB 250605A: Enhanced Swift-XRT position
  92. GRB 250605A: Swift detection of a burst
  93. IPN triangulation of GRB 250404B
  94. IPN triangulation of GRB 250529A
  95. GRB 250601A: PRIME H band upper limit.
  96. GRB 250601A: PRIME J band upper limit.
  97. GRB 250601A: VLT/FORS2 Optical Observation
  98. GRB 250601A: Fermi GBM Observation
  99. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  100. GRB 250603A: Swift/UVOT Upper Limits

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