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"
  1. EP250508a: Liverpool Telescope optical upper limits
  2. EP250508a: follow-up observation with EP-FXT
  3. EP250508a: SVOM/VT optical candidate
  4. EP250508a: KAIT optical upper limit
  5. GRB 250507A: KAIT optical upper limit
  6. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 250505B: SVOM/GRM observation of a short burst
  8. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  9. GRB 250506A: GECAM detection
  10. EP250508a: REM optical/NIR observations
  11. GRB 250506A: Swift-XRT afterglow detection
  12. EP250508a: Global MASTER-Net observations report
  13. GRB 250506A: SVOM/VT optical upper limit
  14. EP250508a: COLIBRÍ Optical Limit
  15. EP250508a: Einstein Probe detection of an X-ray transient
  16. GRB 250507A: Swift-XRT refined Analysis
  17. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  18. GRB 250506A: Swift/UVOT Upper Limits
  19. GRB 250427B : SVOM detection of a burst through offline search
  20. GRB 250507A: follow-up observation with EP-FXT
  21. GRB 250430A / EP250430a: AstroSat CZTI detection
  22. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  23. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  24. GRB 250507A: refined SVOM/MXT data analysis
  25. GRB 250507A: REM optical/NIR observations
  26. GRB 250507A: SVOM/VT optical upper limit
  27. GRB 250506A: Swift-XRT observations
  28. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  29. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  31. GRB 250507A: SVOM detection of a long burst
  32. GRB 250506A: Mephisto optical upper limits
  33. GRB 250504A: EIRSAT-1 GMOD Detection
  34. GRB 250506A: Swift ToO observations
  35. GRB 250502A: Bassano Bresciano Observatory upper limit
  36. IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event
  37. IceCube Alert 250506.59: Global MASTER-Net observations report
  38. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  39. GRB 250506A: Xinglong 2.16m optical upper limit
  40. SVOM/sb25050601: EP-FXT observations
  41. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  42. GRB 250506A: REM optical/NIR upper limits
  43. GRB 250506A: Fermi GBM Observation
  44. GRB 250506A: Swift XRT observations and possible counterpart detection
  45. GRB 250506A: TRT optical observations
  46. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  47. GRB 250506A: SVOM detection of a burst
  48. GRB 250504A: Swift-BAT refined analysis
  49. GRB 250430A: Swift-BAT refined analysis
  50. GRB 250506A: Fermi GBM Final Real-time Localization
  51. GRB 250504A: Swift-XRT refined Analysis
  52. GRB 250504A: VLT/X-shooter upper limits
  53. Fermi GRB 250505A: Global MASTER-Net observations report
  54. GRB 250504A: SVOM/VT upper limit
  55. GRB 250504A: REM optical/NIR observations
  56. GRB 250502A: REM optical/NIR observations
  57. GRB 250505A: Fermi GBM Final Real-time Localization
  58. GRB 250504A: MeerLICHT optical afterglow detection
  59. GRB 250504A: Fermi GBM Observation
  60. GRB 250504A: Enhanced Swift-XRT position
  61. Fermi GRB 250504A: Global MASTER-Net observations report
  62. GRB 250504A: Swift detection of a burst
  63. GRB 250504A: Fermi GBM Final Real-time Localization
  64. Swift GRB250504.98: Global MASTER-Net observations report
  65. GRB 250502A: Swift/UVOT Follow up
  66. GRB 250502A: Mondy and Tien-Shan Optical Observations
  67. GRB 250502A: KAIT optical observations
  68. GRB 250502A: Montarrenti Observatory optical detection
  69. GRB 250502A: Swift-XRT afterglow detection
  70. Fermi trigger No 767975731: Global MASTER-Net observations report
  71. GRB 250502A: NOT optical observations
  72. GRB 250502a: Liverpool Telescope optical follow-up
  73. GRB 250502B: AstroSat CZTI detection
  74. GRB 250502A: AKO Optical Afterglow Detection
  75. GRB 250502A: LCO optical counterpart detection
  76. GRB 250502A: Swift ToO observations
  77. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  78. GRB 250502C: Fermi GBM Final Localization
  79. GRB 250407A: VZLUSAT-2 detection
  80. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  81. GRB 250502B: DDOTI Optical Observations
  82. GRB 250430A: Swift-XRT refined Analysis
  83. GRB 250502A: Early optical counterpart detection by LCO.
  84. GRB 250430A: Swift/UVOT Detection
  85. GRB 250502A: SVOM/VT optical bump
  86. GRB 250502A: TRT optical afterglow confirmation
  87. GRB 250430A: Enhanced Swift-XRT position
  88. Fermi GRB 250502B: Global MASTER-Net observations report
  89. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  90. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  91. GRB 250502B: Fermi GBM Final Real-time Localization
  92. GRB 250502A: SVOM detection of a burst
  93. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  94. GRB 250430A: SVOM/VT optical observations
  95. GRB 250430A: KAIT optical observations
  96. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  97. GRB 250430A / EP250430a: J-band upper limits with WINTER
  98. GRB 250430A: NUTTelA-TAO Early Measurements
  99. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  100. GRB 250430A: DDOTI Optical Observations

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