Skip to main content
End of Swift Science Operations, CHIME Notices Unavailable During Upgrade. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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 261026A: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. GRB 261026B: Fermi GBM Final Real-time Localization
  3. GRB 261024A: NuSTAR detection of prompt emission
  4. GRB 261026A: SVOM detection of a burst
  5. GRB 261025B: Fermi GBM Final Real-time Localization
  6. EP261025a: J-band upper limit with WINTER
  7. EP261023a: J-band upper limit with WINTER
  8. EP 261025a: COLIBRÍ optical upper limit
  9. EP261025a: Einstein Probe detection of a fast X-ray transient
  10. GRB 261025A: Fermi GBM Final Localization Correction
  11. EP261023a: J band upper limit by SYSU 80cm infrared telescope
  12. GRB 261024B: Fermi GBM Final Real-time Localization
  13. EP261015a: VST optical observations
  14. GRB 261024A: BALROG localization (Fermi Trigger 814551785 / GRB 261024683)
  15. GRB 261024A: Fermi GBM Final Real-time Localization
  16. EP261023a: Mondy optical upper limit
  17. EP261015a: MAO/AZT-22 optical observations
  18. EP261015a: VLA non-detection
  19. EP261023a: NOT optical counterpart candidate
  20. EP261023a: Einstein Probe detection of an X-ray transient
  21. GRB 261019A: Insight-HXMT/HE detection
  22. The EP-WXT trigger 01709321472 is likely a flaring star
  23. IceCube-261020A: Upper limits from a search for additional neutrino events in IceCube
  24. NuSTAR 261020, a 830s hard X-ray transient
  25. EP261015a: GSP multiband optical follow-up observations
  26. GRB 261017A: SVOM/GRM observation
  27. GRB 261021A: Fermi GBM Final Real-time Localization
  28. EP261015a: Further optical observations with the 1.3m DFOT
  29. GRB 261020B: AstroSat CZTI detection of a short burst
  30. Fermi-LAT Gamma-ray Observations of IceCube-261020A
  31. EP261015a: AZT-20 Assy-Turgen optical observations
  32. GRB 261020A: Fermi GBM Observation
  33. GRB 261017A: SAO RAS optical upper limit
  34. EP261015a: Wendelstein 43 cm optical observations
  35. GRB 260903A
  36. EP261015a: Follow-up with the 1.3m DFOT
  37. EP261015a: Terskol Zeiss-2000 optical upper limit
  38. EP261007b: Further EP-FXT follow-up observations
  39. GRB 261017A: COLIBRÍ optical upper limit
  40. IceCube-261020A - IceCube observation of a high-energy neutrino candidate track-like event
  41. GRB 261020A: MAXI GSC detection
  42. GRB 261020A: Fermi GBM Final Real-time Localization
  43. EP261015a: COLIBRÍ optical observations of a rebrightening
  44. Konus-Wind detection of GRB 261017A
  45. GRB 261019A: Fermi GBM Final Localization
  46. GRB 261017A: Possible Swift/UVOT Detection
  47. GRB 261017A: Luminance-band upper limit from a 28cm telescope in Chengde
  48. GRB 261017A: R-band upper limit with the 1.3-m DFOT
  49. GRB 261017A: Swift-BAT refined analysis
  50. GRB 261017A: a short minimum variability timescale compatible with a compact object merger origin
  51. EP261015b: NOT Optical Observations
  52. GRB 261017A: J band upper limit by the SYSU 80cm infrared telescope
  53. EP261015c: refined analysis of the EP-FXT observation favors a stellar flare interpretation
  54. GRB 261017A : MITSuME Akeno optical upper limits
  55. GRB 261017A: Swift-XRT refined Analysis
  56. GRB 261017A: Nanshan/NEXT optical upper limit
  57. GRB 261017A: Enhanced Swift-XRT position
  58. GRB 261017A: Fermi GBM Observation
  59. GRB261010A: Retraction of Keck/MOSFIRE near-IR source
  60. GRB 261017A: Swift detection of a burst
  61. GRB 261017A: Fermi GBM Final Real-time Localization
  62. EP261015a: Tentative fading of the candidate optical counterpart from the NOT
  63. EP261015b: Refined analysis of EP-FXT observations
  64. EP261015b: J-band upper limit by the SYSU 80cm infrared telescope
  65. EP261015a: refined analysis of EP-FXT observations
  66. EP261015c: J-band upper limit with WINTER
  67. EP261015a: J-band upper limit with WINTER
  68. EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
  69. GRB 261011A: 1.3m DFOT optical upper limit
  70. GRB 261010A: Pan-STARRS z-band imaging and upper limit
  71. EP261015a: SVOM/VT optical observation
  72. EP241111a and EP250125a: Upper limits from SVOM/GRM Observations
  73. GRB 261010A: VLA radio observations
  74. EP261015a: COLIBRÍ optical observations
  75. EP261015c: Einstein Probe detection of a fast X-ray transient
  76. EP261015b: Einstein Probe detection of an X-ray transient
  77. GRB261010A: Keck/MOSFIRE detection of a near-IR source
  78. EP261015a: Einstein Probe detection of a fast X-ray transient
  79. EP261015a (WXT 11900947714): Possible optical counterpart from NOT and LCO
  80. The EP-WXT trigger 01709321333 is likely a flaring star
  81. GRB 261010A: ASKAP non-detection of a radio afterglow
  82. GRB 261010A: LBT tentative near-infrared detection
  83. GRB 261011A: SAO RAS and AbAO optical observations
  84. GRB 261010A: Glowbug gamma-ray detection
  85. GRB 261008A: SVOM/GRM observation
  86. GRB 261009A: GECAM-B detection of a burst
  87. EP261006a : MeerKAT radio observations.
  88. IceCube-261012A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
  90. GRB 261010A: a short minimum variability timescale and a distinct pulse evolution compatible with a merger origin
  91. GRB 261013A: Fermi GBM Final Real-time Localization
  92. GRB 261011A: Later-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  93. Fermi-LAT Gamma-ray Observations of IceCube-261012A
  94. GRID detection of GRB 261010A
  95. GRB 261011A: GECAM-B observation
  96. GRB 261011B: GECAM-B observation
  97. GRB 261010A: J-band upper limit by the SYSU 80cm infrared telescope
  98. IceCube-260919A: No transient candidates from the Zwicky Transient Facility
  99. GRB 261010A: Swift-XRT refined Analysis
  100. GRB 261011A: Swift-XRT refined Analysis

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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