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. EP261015a: AZT-20 Assy-Turgen optical observations
  2. GRB 261020A: Fermi GBM Observation
  3. GRB 261017A: SAO RAS optical upper limit
  4. EP261015a: Wendelstein 43 cm optical observations
  5. GRB 260903A
  6. EP261015a: Follow-up with the 1.3m DFOT
  7. EP261015a: Terskol Zeiss-2000 optical upper limit
  8. EP261007b: Further EP-FXT follow-up observations
  9. GRB 261017A: COLIBRÍ optical upper limit
  10. IceCube-261020A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 261020A: MAXI GSC detection
  12. GRB 261020A: Fermi GBM Final Real-time Localization
  13. EP261015a: COLIBRÍ optical observations of a rebrightening
  14. Konus-Wind detection of GRB 261017A
  15. GRB 261019A: Fermi GBM Final Localization
  16. GRB 261017A: Possible Swift/UVOT Detection
  17. GRB 261017A: Luminance-band upper limit from a 28cm telescope in Chengde
  18. GRB 261017A: R-band upper limit with the 1.3-m DFOT
  19. GRB 261017A: Swift-BAT refined analysis
  20. GRB 261017A: a short minimum variability timescale compatible with a compact object merger origin
  21. EP261015b: NOT Optical Observations
  22. GRB 261017A: J band upper limit by the SYSU 80cm infrared telescope
  23. EP261015c: refined analysis of the EP-FXT observation favors a stellar flare interpretation
  24. GRB 261017A : MITSuME Akeno optical upper limits
  25. GRB 261017A: Swift-XRT refined Analysis
  26. GRB 261017A: Nanshan/NEXT optical upper limit
  27. GRB 261017A: Enhanced Swift-XRT position
  28. GRB 261017A: Fermi GBM Observation
  29. GRB261010A: Retraction of Keck/MOSFIRE near-IR source
  30. GRB 261017A: Swift detection of a burst
  31. GRB 261017A: Fermi GBM Final Real-time Localization
  32. EP261015a: Tentative fading of the candidate optical counterpart from the NOT
  33. EP261015b: Refined analysis of EP-FXT observations
  34. EP261015b: J-band upper limit by the SYSU 80cm infrared telescope
  35. EP261015a: refined analysis of EP-FXT observations
  36. EP261015c: J-band upper limit with WINTER
  37. EP261015a: J-band upper limit with WINTER
  38. EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
  39. GRB 261011A: 1.3m DFOT optical upper limit
  40. GRB 261010A: Pan-STARRS z-band imaging and upper limit
  41. EP261015a: SVOM/VT optical observation
  42. EP241111a and EP250125a: Upper limits from SVOM/GRM Observations
  43. GRB 261010A: VLA radio observations
  44. EP261015a: COLIBRÍ optical observations
  45. EP261015c: Einstein Probe detection of a fast X-ray transient
  46. EP261015b: Einstein Probe detection of an X-ray transient
  47. GRB261010A: Keck/MOSFIRE detection of a near-IR source
  48. EP261015a: Einstein Probe detection of a fast X-ray transient
  49. EP261015a (WXT 11900947714): Possible optical counterpart from NOT and LCO
  50. The EP-WXT trigger 01709321333 is likely a flaring star
  51. GRB 261010A: ASKAP non-detection of a radio afterglow
  52. GRB 261010A: LBT tentative near-infrared detection
  53. GRB 261011A: SAO RAS and AbAO optical observations
  54. GRB 261010A: Glowbug gamma-ray detection
  55. GRB 261008A: SVOM/GRM observation
  56. GRB 261009A: GECAM-B detection of a burst
  57. EP261006a : MeerKAT radio observations.
  58. IceCube-261012A: Upper limits from a search for additional neutrino events in IceCube
  59. GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
  60. GRB 261010A: a short minimum variability timescale and a distinct pulse evolution compatible with a merger origin
  61. GRB 261013A: Fermi GBM Final Real-time Localization
  62. GRB 261011A: Later-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  63. Fermi-LAT Gamma-ray Observations of IceCube-261012A
  64. GRID detection of GRB 261010A
  65. GRB 261011A: GECAM-B observation
  66. GRB 261011B: GECAM-B observation
  67. GRB 261010A: J-band upper limit by the SYSU 80cm infrared telescope
  68. IceCube-260919A: No transient candidates from the Zwicky Transient Facility
  69. GRB 261010A: Swift-XRT refined Analysis
  70. GRB 261011A: Swift-XRT refined Analysis
  71. GRB 261011A: Enhanced Swift-XRT position
  72. GRB 261010A: a Type I-L (merger-driven) GRB candidate
  73. GRB 261011A: 10.4m GTC spectroscopic redshift (z = 2.407)
  74. GRB 261011A: Swift-BAT refined analysis
  75. IceCube-261012A - IceCube observation of a high-energy neutrino candidate track-like event
  76. GRB 261010A: 10.4m GTC spectroscopy of the galaxy 2" from the afterglow
  77. MAXI GRB261012.23: Global MASTER-Net observations report
  78. GRB 261011A: REM optical/NIR observations
  79. Konus-Wind detection of GRB 261010A
  80. Konus-Wind detection of GRB 261011A
  81. Konus-Wind detection of GRB 261007A/EP261007a
  82. GRB 261011A: SOAR optical afterglow observations at ~17 hours
  83. EP261006a: 10 GHz VLA observations
  84. GRB 261011A: VLT/X-shooter redshift constraints
  85. GRB 261012A: MAXI GSC detection
  86. GRB 261010A: Swift-BAT refined analysis
  87. GRB 261011A : MITSuME Akeno optical afterglow candidate detection
  88. GRB 261011A: Optical followup from Sichuan South Observatory
  89. GRB 261011A: GMG Optical Observation
  90. GRB 261011A: Liverpool Telescope optical observations
  91. GRB 261011A: J-band observations by the SYSU 80cm infrared telescope
  92. GRB 261010A: NOT confirmation of the optical afterglow
  93. GRB 261010A: Fermi GBM Observation
  94. GRB 261011B: Fermi GBM Final Localization
  95. GRB 261011A: continued LCO optical observations
  96. EP261007b: Global MASTER-Net observations report
  97. GRB 261011A: GROWTH-India Telescope optical observations
  98. GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde
  99. Swift GRB 261011A: Global MASTER-Net observations report
  100. GRB 261011A: Optical follow-up observations with Kinder

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