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 261020A: Fermi GBM Final Real-time Localization
  2. EP261015a: COLIBRÍ optical observations of a rebrightening
  3. Konus-Wind detection of GRB 261017A
  4. GRB 261019A: Fermi GBM Final Localization
  5. GRB 261017A: Possible Swift/UVOT Detection
  6. GRB 261017A: Luminance-band upper limit from a 28cm telescope in Chengde
  7. GRB 261017A: R-band upper limit with the 1.3-m DFOT
  8. GRB 261017A: Swift-BAT refined analysis
  9. GRB 261017A: a short minimum variability timescale compatible with a compact object merger origin
  10. EP261015b: NOT Optical Observations
  11. GRB 261017A: J band upper limit by the SYSU 80cm infrared telescope
  12. EP261015c: refined analysis of the EP-FXT observation favors a stellar flare interpretation
  13. GRB 261017A : MITSuME Akeno optical upper limits
  14. GRB 261017A: Swift-XRT refined Analysis
  15. GRB 261017A: Nanshan/NEXT optical upper limit
  16. GRB 261017A: Enhanced Swift-XRT position
  17. GRB 261017A: Fermi GBM Observation
  18. GRB261010A: Retraction of Keck/MOSFIRE near-IR source
  19. GRB 261017A: Swift detection of a burst
  20. GRB 261017A: Fermi GBM Final Real-time Localization
  21. EP261015a: Tentative fading of the candidate optical counterpart from the NOT
  22. EP261015b: Refined analysis of EP-FXT observations
  23. EP261015b: J-band upper limit by the SYSU 80cm infrared telescope
  24. EP261015a: refined analysis of EP-FXT observations
  25. EP261015c: J-band upper limit with WINTER
  26. EP261015a: J-band upper limit with WINTER
  27. EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
  28. GRB 261011A: 1.3m DFOT optical upper limit
  29. GRB 261010A: Pan-STARRS z-band imaging and upper limit
  30. EP261015a: SVOM/VT optical observation
  31. EP241111a and EP250125a: Upper limits from SVOM/GRM Observations
  32. GRB 261010A: VLA radio observations
  33. EP261015a: COLIBRÍ optical observations
  34. EP261015c: Einstein Probe detection of a fast X-ray transient
  35. EP261015b: Einstein Probe detection of an X-ray transient
  36. GRB261010A: Keck/MOSFIRE detection of a near-IR source
  37. EP261015a: Einstein Probe detection of a fast X-ray transient
  38. EP261015a (WXT 11900947714): Possible optical counterpart from NOT and LCO
  39. The EP-WXT trigger 01709321333 is likely a flaring star
  40. GRB 261010A: ASKAP non-detection of a radio afterglow
  41. GRB 261010A: LBT tentative near-infrared detection
  42. GRB 261011A: SAO RAS and AbAO optical observations
  43. GRB 261010A: Glowbug gamma-ray detection
  44. GRB 261008A: SVOM/GRM observation
  45. GRB 261009A: GECAM-B detection of a burst
  46. EP261006a : MeerKAT radio observations.
  47. IceCube-261012A: Upper limits from a search for additional neutrino events in IceCube
  48. GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
  49. GRB 261010A: a short minimum variability timescale and a distinct pulse evolution compatible with a merger origin
  50. GRB 261013A: Fermi GBM Final Real-time Localization
  51. GRB 261011A: Later-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  52. Fermi-LAT Gamma-ray Observations of IceCube-261012A
  53. GRID detection of GRB 261010A
  54. GRB 261011A: GECAM-B observation
  55. GRB 261011B: GECAM-B observation
  56. GRB 261010A: J-band upper limit by the SYSU 80cm infrared telescope
  57. IceCube-260919A: No transient candidates from the Zwicky Transient Facility
  58. GRB 261010A: Swift-XRT refined Analysis
  59. GRB 261011A: Swift-XRT refined Analysis
  60. GRB 261011A: Enhanced Swift-XRT position
  61. GRB 261010A: a Type I-L (merger-driven) GRB candidate
  62. GRB 261011A: 10.4m GTC spectroscopic redshift (z = 2.407)
  63. GRB 261011A: Swift-BAT refined analysis
  64. IceCube-261012A - IceCube observation of a high-energy neutrino candidate track-like event
  65. GRB 261010A: 10.4m GTC spectroscopy of the galaxy 2" from the afterglow
  66. MAXI GRB261012.23: Global MASTER-Net observations report
  67. GRB 261011A: REM optical/NIR observations
  68. Konus-Wind detection of GRB 261010A
  69. Konus-Wind detection of GRB 261011A
  70. Konus-Wind detection of GRB 261007A/EP261007a
  71. GRB 261011A: SOAR optical afterglow observations at ~17 hours
  72. EP261006a: 10 GHz VLA observations
  73. GRB 261011A: VLT/X-shooter redshift constraints
  74. GRB 261012A: MAXI GSC detection
  75. GRB 261010A: Swift-BAT refined analysis
  76. GRB 261011A : MITSuME Akeno optical afterglow candidate detection
  77. GRB 261011A: Optical followup from Sichuan South Observatory
  78. GRB 261011A: GMG Optical Observation
  79. GRB 261011A: Liverpool Telescope optical observations
  80. GRB 261011A: J-band observations by the SYSU 80cm infrared telescope
  81. GRB 261010A: NOT confirmation of the optical afterglow
  82. GRB 261010A: Fermi GBM Observation
  83. GRB 261011B: Fermi GBM Final Localization
  84. GRB 261011A: continued LCO optical observations
  85. EP261007b: Global MASTER-Net observations report
  86. GRB 261011A: GROWTH-India Telescope optical observations
  87. GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde
  88. Swift GRB 261011A: Global MASTER-Net observations report
  89. GRB 261011A: Optical follow-up observations with Kinder
  90. GRB 261011A: SVOM/C-GFT optical observations
  91. EP261007b: Second EP-FXT follow-up observation and a possible X-ray counterpart to the optical transient
  92. GRB 261011A: LCO optical observations
  93. GRB 261011A: SVOM/VT optical observation from VHF data
  94. GRB 261011A: LCO optical observations
  95. GRB 261011A: TRT optical afterglow detection
  96. GRB 261011A: GOTO optical counterpart detection
  97. GRB 261011A: Swift detection of an unusual burst
  98. GRB 261011A: SVOM detection of a long bright burst
  99. GRB 261010A: Enhanced Swift-XRT position
  100. EP261010a: refined analysis of the EP-WXT and autonomous EP-FXT observations

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