Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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 250920C: Swift/UVOT Detection
  2. GRB 250920B: Fermi GBM Observation
  3. GRB 250920A: Fermi GBM Detection
  4. GRB 250920C: Fermi GBM Observation
  5. Swift GRB 250920C: Global MASTER-Net observations report
  6. GRB 250920B: Swift/UVOT Detection
  7. GRB 250920B: FTW optical and NIR observations of the counterpart
  8. GRB 250920C: Optical counterpart detection by LCO
  9. GRB 250920A: SVOM/GRM observation
  10. GRB250920C: LCOGT Optical Detection
  11. GRB 250920B: Enhanced Swift-XRT position
  12. GRB 250920B: Swift-XRT refined Analysis
  13. GRB 250920B: SVOM/C-GFT optical observations
  14. GRB 250920C: GOTO optical counterpart candidate
  15. GRB 250919A / EP250919a: LCO optical observation
  16. Konus-Wind detection of GRB 250919A
  17. GRB 250920C: Swift detection of a burst
  18. GRB 250920C: Fermi GBM Final Real-time Localization
  19. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  20. Swift GRB 250920B: Global MASTER-Net observations report
  21. GRB 250919A / EP250919a: Insight-HXMT detection
  22. GRB 250920A: AstroSat CZTI detection
  23. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  24. GRB 250920B: Fermi GBM Final Real-time Localization
  25. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  26. GRB 250920A: Fermi GBM Final Localization
  27. GRB 250919A/EP250919a: SVOM/VT optical observation
  28. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  29. GRB 250916A: Mondy R-band optical observations
  30. GRB 250919A: Glowbug gamma-ray detection
  31. GRB 250919A: Fermi GBM Observation
  32. Fermi GRB 250918A: Global MASTER-Net observations report
  33. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  34. GRB 250918A: SVOM/GRM observation
  35. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  36. GRB 250919A: Swift-XRT afterglow detection
  37. GRB 250919A: Fermi-LAT detection
  38. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  39. GRB 250919A: SVOM/GRM observation of a very bright GRB
  40. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  41. EP250919a: Global MASTER-Net observations report
  42. EP250919a: Einstein Probe detection of an X-ray transient
  43. Correction for GCN 41877: EP-WXT ID is 01709243841
  44. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  45. GRB 250916A: Fermi GBM Observation
  46. Fermi GRB 250919A: Global MASTER-Net observations report
  47. GRB 250919A: Fermi GBM Final Real-time Localization
  48. GRB 250916A: KAIT optical observations
  49. GRB 250917B: VLT/HAWK-I near-infrared observations
  50. GRB 250916A: NuSTAR detection of the prompt emission
  51. GRB 250916A: further SAO RAS optical observations
  52. GRB 250912A: SVOM/ECLAIRs refined analysis
  53. GRB 250917B: Swift-BAT refined analysis
  54. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  55. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  56. GRB 250918A: Fermi GBM Final Real-time Localization
  57. GRB 250917B: Swift/UVOT Upper Limits
  58. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  59. GRB 250916A: Swift-XRT observations
  60. EP250916a: EP-FXT follow-up observation
  61. GRB 250916A: MAO/AZT-22 optical observations
  62. GRB 250916A: SAO RAS optical observations
  63. GRB 250916A : GIT optical observations
  64. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  65. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  66. GRB 250916A: Glowbug gamma-ray detection
  67. GRB250917B: WFST optical observations
  68. GRB 250916A: Swift ToO observations
  69. GRB 250917B: Fermi GBM Observation
  70. GRB 250917B: Swift-XRT observations
  71. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  72. Fermi GRB 250917B: Global MASTER-Net observations report
  73. GRB 250917B: Swift detection of a short burst
  74. GRB 250916A: GOTO optical counterpart candidate
  75. GRB 250917B: Fermi GBM Final Real-time Localization
  76. GRB 250917A: Fermi GBM Final Real-time Localization
  77. The EP-WXT trigger 01709241037 is likely a flaring star
  78. GRB 250916A: AstroSat CZTI detection of a bright long burst
  79. GRB 250910A: SVOM/ECLAIRs refined analysis
  80. EP250916a: Einstein Probe detection of an X-ray transient
  81. Fermi GRB 250916A: Global MASTER-Net observations report
  82. GRB 250916A: Fermi GBM Final Real-time Localization
  83. EP250827b: VLA Observations
  84. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  85. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  86. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  87. SVOM/sb25091517: SVOM detection of an X-ray transient
  88. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  89. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. GRB 250912A: Swift-XRT observations
  91. GRB250912A: VLT/HAWK-I follow-up observations
  92. GRB 250912A: VLT observations
  93. GRB 250912A: Fermi GBM Observation
  94. GRB 250911A: Insight-HXMT detection
  95. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  96. GRB 250912A:SVOM/VT optical upper limit
  97. GRB 250912A: LCO optical upper limit
  98. The EP-WXT trigger 01709240768 is likely a flaring star
  99. Fermi GRB 250912A: Global MASTER-Net observations report
  100. EP250911a: Global MASTER-Net observations report

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