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"

32486 results found.

  1. Fermi-LAT gamma-ray observations of IceCube-250421A
  2. GRB 250424A: Skynet Optical Observations
  3. GRB 250424A: Kilonova-Catcher optical afterglow detection
  4. GRB 250419a: Continued Liverpool Telescope observations
  5. GRB 250419A: Liverpool Telescope optical upper limit
  6. GRB 250407A: GRBAlpha detection
  7. GRB 250404A / EP250404a: GRBAlpha detection
  8. GRB 250330B: GRBAlpha detection
  9. GRB 250419A: SVOM/ECLAIRs refined analysis
  10. GRB 250424A: AstroSat CZTI detection of a bright long burst
  11. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  12. GRB 250424A: BlackGEM optical afterglow detection
  13. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  14. GRB 250424A: likely host galaxy
  15. GRB 250424A: DDOTI Afterglow Detection
  16. GRB 250424A: REM optical/NIR afterglow detection
  17. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  18. EP250421a: Nickel optical upper limit
  19. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  20. EP250421a: Upper limits from Fermi-GBM Observations
  21. SVOM/sb25042207: XRT observations
  22. SVOM/sb25042207: BOOTES-2 early optical upper limit
  23. SVOM/sb25042207: GOTO optical upper limits
  24. GRB 250421A: AstroSat CZTI detection
  25. GRB250419A: VLA radio detection
  26. IceCube-250421A: DDOTI Detection of the LAST Candidate
  27. GRB 250419A: Mephisto Multi-band Optical Detection
  28. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  29. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  30. EP250421a: NOT optical observations
  31. GRB 250419A: Optical Observations via Virtual Telescope Project
  32. EP250421a: REM optical upper limit
  33. EP250421a: Swift/XRT counterpart detection
  34. EP250421A: COLIBRÍ Optical Upper Limit
  35. GRB 250419A: Mondy Continued Optical Observations
  36. Fermi GRB 250421A: Global MASTER-Net observations report
  37. EP250421a: Global MASTER-Net observations report
  38. EP250421a: Mephisto optical counterpart confirmation
  39. GRB 250419A: Liverpool Telescope observations
  40. GRB 250419A: LCO optical observation
  41. GRB 250419A: JinShan optical observations
  42. GRB 250419A: SVOM/VT optical continuous observations
  43. GRB 250419A: SVOM/C-GFT optical observations
  44. GRB 250419A: Swift/UVOT Follow up
  45. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  46. GRB 250419A: LCO optical afterglow multi-band observations
  47. GRB 250419A: Mondy and AbAO Optical Observations
  48. GRB 250419A: Liverpool Telescope observations
  49. GRB 250419A: AKO Optical Afterglow Detection
  50. GRB 250419A: MASTER optical afterglow observation
  51. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  52. GRB 250407A: rest-frame energetics from Konus-Wind observation
  53. GRB 250419A: Swift-XRT localisation
  54. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  55. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  56. GRB 250419A: Swift-XRT refined Analysis
  57. GRB 250419A: GOTO optical counterpart detection
  58. GRB 250419A: KAIT optical afterglow observations
  59. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  60. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  61. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  62. EP250416a: Swift/XRT counterpart fading
  63. EP250416a: refined EP-WXT and EP-FXT analysis
  64. Konus-Wind detection of GRB 250403A
  65. EP20250416a: Swift/XRT counterpart detection
  66. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  67. IceCube-250416A: DDOTI Optical Observations
  68. EP250416a: Gemini South-GMOS optical counterpart
  69. EP250225a: SVOM/VT optical brightening
  70. SVOM/sb25041603 is not a GRB
  71. EP250416a: GSP optical upper limit
  72. EP250416a: Global MASTER-Net observations report
  73. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  74. GRB 250413A: AstroSat CZTI detection
  75. EP250304a: ATCA radio observations
  76. EP250404a: Nanshan 0.43m Telescope optical observatios
  77. GRB 250411A: DDOTI Optical Observations
  78. Fermi GRB 250411A: Global MASTER-Net observations report
  79. GRB 250407A: Continued KAIT/Nickel optical observations
  80. GRB 250314A: e-MERLIN observations
  81. GRB 250407A: Mondy and AbAO Optical Observations
  82. EP250227a: Further NOT optical observations
  83. GRB 250320B: cubesat Avion detection
  84. IceCube-250406A: Swift-XRT observations
  85. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  86. IPN triangulation of GRB 250407A
  87. EP250407a: Global MASTER-Net observations report
  88. GRB 250407A: LCO detection of a fading optical counterpart
  89. Fermi-LAT gamma-ray observations of IceCube-250406A
  90. EP250407a: Swift-XRT observations
  91. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  92. Konus-Wind detection of GRB 250407A
  93. GRB 250407A: SVOM/GRM observation of a bright long burst
  94. GRB 250407A: EP-WXT afterglow detection
  95. EP250407a: EP-WXT detection of a fast X-ray transient
  96. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  97. GRB 250407A: KAIT Optical Afterglow Candidate
  98. IceCube-250406A: No candidates from the Zwicky Transient Facility
  99. GRB 250407A: Fermi GBM Detection
  100. GRB 250407A: Swift-XRT afterglow detection

Advanced

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