Skip to main content
New! BOOM Notices and Schema v7.0.0. 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"

35437 results found.

  1. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  2. GRB 250502C: Fermi GBM Final Localization
  3. GRB 250407A: VZLUSAT-2 detection
  4. GRB 250502B: DDOTI Optical Observations
  5. GRB 250430A: Swift-XRT refined Analysis
  6. GRB 250502A: Early optical counterpart detection by LCO.
  7. GRB 250430A: Swift/UVOT Detection
  8. GRB 250502A: SVOM/VT optical bump
  9. GRB 250502A: TRT optical afterglow confirmation
  10. GRB 250430A: Enhanced Swift-XRT position
  11. Fermi GRB 250502B: Global MASTER-Net observations report
  12. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  13. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  14. GRB 250502B: Fermi GBM Final Real-time Localization
  15. GRB 250502A: SVOM detection of a burst
  16. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  17. GRB 250430A: SVOM/VT optical observations
  18. GRB 250430A: KAIT optical observations
  19. GRB 250430A / EP250430a: J-band upper limits with WINTER
  20. GRB 250430A: NUTTelA-TAO Early Measurements
  21. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  22. GRB 250430A: DDOTI Optical Observations
  23. GRB 250430A: Leavitt Observatory optical upper limit
  24. GRB 250430A: Bassano Bresciano Observatory upper limit
  25. GRB 250430A : MITSuME Akeno optical upper limits
  26. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  27. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  28. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  29. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  30. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 250430A: AKO Optical Afterglow Detection
  32. GRB 250430A: Kanata optical upper limit
  33. EP 250427A: Optical counterpart detection by LCO.
  34. GRB 250430A: Swift detection of a burst with optical counterpart
  35. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  36. EP250428b: SAO RAS optical upper limit
  37. GRB 250427A: Swift/UVOT Detection
  38. EP250427a / GRB 250427A: OHP/T193 photometric observations
  39. EP250427a: EP-FXT follow-up observations
  40. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  41. GRB250427A/EP250427a GIT optical afterglow detection:
  42. GRB 250427A: Swift-XRT refined Analysis
  43. EP250427a / GRB 250427A: LCO optical counterpart detection
  44. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  45. EP250427A/GRB250427A: Keck/LRIS redshift
  46. GRB 250424A: LCO optical observation
  47. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  48. GRB 250424A: Swift-BAT refined analysis
  49. GRB 250424A: SVOM/GRM observation of a long burst
  50. GRB 250424A: PRIME near-infrared detection
  51. GRB 250424A: WINTER J-band detection
  52. GRB 250424A: EIRSAT-1 GMOD Detection
  53. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  54. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 250424A: SVOM/VT optical observation
  56. GRB 250419A: Mondy Optical Observations
  57. GRB 250424A: Swift/UVOT Detection
  58. Konus-Wind detection of GRB 250424A
  59. GRB 250424A: Skynet Optical Observations
  60. GRB 250424A: Kilonova-Catcher optical afterglow detection
  61. GRB 250419a: Continued Liverpool Telescope observations
  62. GRB 250419A: Liverpool Telescope optical upper limit
  63. GRB 250407A: GRBAlpha detection
  64. GRB 250404A / EP250404a: GRBAlpha detection
  65. GRB 250330B: GRBAlpha detection
  66. GRB 250419A: SVOM/ECLAIRs refined analysis
  67. GRB 250424A: Swift-XRT refined Analysis
  68. GRB 250424A: Enhanced Swift-XRT position
  69. GRB 250424A: AstroSat CZTI detection of a bright long burst
  70. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  71. GRB 250424A: BlackGEM optical afterglow detection
  72. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  73. GRB 250424A: likely host galaxy
  74. GRB 250424A: DDOTI Afterglow Detection
  75. GRB 250424A: REM optical/NIR afterglow detection
  76. GRB 250424A: Swift detection of a burst with an optical counterpart
  77. Swift GRB 250424A: Global MASTER-Net observations report
  78. Swift GRB 250424A: Global MASTER-Net OT detection
  79. EP250421a: Nickel optical upper limit
  80. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  81. EP250421a: Upper limits from Fermi-GBM Observations
  82. SVOM/sb25042207: BOOTES-2 early optical upper limit
  83. SVOM/sb25042207: GOTO optical upper limits
  84. GRB 250421A: AstroSat CZTI detection
  85. GRB250419A: VLA radio detection
  86. GRB 250419A: Mephisto Multi-band Optical Detection
  87. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  88. GRB 250419A: Optical Observations via Virtual Telescope Project
  89. GRB 250419A: Mondy Continued Optical Observations
  90. Fermi GRB 250421A: Global MASTER-Net observations report
  91. GRB 250421B: AstroSat CZTI detection of a bright long burst
  92. GRB 250421A: Fermi GBM Final Real-time Localization
  93. GRB 250419A: Liverpool Telescope observations
  94. GRB 250419A: LCO optical observation
  95. GRB 250419A: JinShan optical observations
  96. GRB 250419A: SVOM/VT optical continuous observations
  97. GRB 250419A: SVOM/C-GFT optical observations
  98. GRB 250419A: Swift/UVOT Follow up
  99. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  100. GRB 250419A: LCO optical afterglow multi-band 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