Skip to main content
New! CHIME and DSA-110 FRB Notices, IceCube Notices and Schema v6.1.1. 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. EP260223a: Liverpool Telescope upper limits
  2. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  3. GRB 260225A: SVOM detection of a burst
  4. EP260224a: Einstein Probe detection of an X-ray transient
  5. EP 260225.148: COLIBRÍ Confirmation of flaring star
  6. EP260223a: Xinglong optical upper limit
  7. The EP-WXT trigger 01709258631 is likely a flaring star
  8. GRB 260223A: Glowbug gamma-ray detection
  9. EP260213a: Mephisto optical upper limits
  10. EP260223a: EP-FXT follow-up observation
  11. sb26021801: SVOM/VT optical upper limits
  12. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  13. sb26021801: SVOM/C-GFT upper limit
  14. EP260223a: COLIBRÍ optical upper limits
  15. EP260223a: Einstein Probe detection of an X-ray transient
  16. GRB 260223A: SVOM/VT optical observation
  17. GRB 260223A: SVOM/GRM observation
  18. GRB 260223A: COLIBRÍ further optical observations and a brightening
  19. EP260221a: Optical upper limit with Kinder observations
  20. GRB 260223A: COLIBRÍ optical observations
  21. GRB 260223A: DDOTI Optical Candidate
  22. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  23. Fermi GRB 260223A: Global MASTER-Net observations report
  24. GRB 260223A: Fermi GBM Final Real-time Localization
  25. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  26. EP260221a: COLIBRÍ optical counterpart candidate
  27. EP260221a: Gemini South z-band upper limit
  28. GRB 260222A: Fermi GBM Final Real-time Localization
  29. EP260221a: Global MASTER-Net observations report
  30. EP260221a: EP-FXT follow-up observation
  31. Fermi GRB 260221B: Global MASTER-Net observations report
  32. GRB 260221B: Fermi GBM Final Real-time Localization
  33. EP-WXT01709258519: Xinglong optical upper limit
  34. EP260221a: Xinglong optical upper limit
  35. Fermi GRB 260221A: Global MASTER-Net observations report
  36. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  37. GRB 260221A: Fermi GBM Final Real-time Localization
  38. EP260221a: GOTO optical upper limit
  39. EP260221a: COLIBRÍ optical upper limit
  40. SVOM alert sb26021801: LCO optical upper limit
  41. EP260221a: Einstein Probe detection of an X-ray transient
  42. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  43. GRB 260219A: AstroSat CZTI detection
  44. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  45. GRB 260219A: GECAM-B observation of a long burst
  46. Fermi GRB 260219A: Global MASTER-Net observations report
  47. GRB 260219A: Fermi GBM Final Real-time Localization
  48. SVOM alert sb26021801: LAST optical upper limit
  49. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. IceCube Alert 260217A: Global MASTER-Net observations report
  51. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  52. GRB 260217A: Fermi GBM Final Localization
  53. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  54. sb26021801: SVOM detection of a long faint X-ray transient
  55. The EP-WXT trigger 01709258455 is likely a flaring star
  56. EP-WXT 01709258455: NOT optical upper limits
  57. EP260214b: Mondy optical observations
  58. EP260214b: 1.3m DFOT optical upper limit
  59. EP260210a: Mondy optical upper limits
  60. Konus-Wind detection of GRB 260212A
  61. GRB 260208A: AbAO and Terskol optical upper limits
  62. GRB 260208A: continued Mondy optical observations
  63. IPN triangulation of GRB 260212A
  64. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  65. GRB 260213A: GECAM-B observation of a short burst
  66. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  67. GRB 260216A: Fermi GBM Final Real-time Localization
  68. EP260214b: Liverpool Telescope optical observations
  69. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  70. EP260214b: Optical upper limit with Kinder observations
  71. EP260214a: Optical upper limits with Kinder observations
  72. EP260214b: EP-FXT follow-up observation
  73. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  74. EP260214b: DDOTI Optical Detection
  75. EP260214b: GROWTH-India Telescope optical upper limit
  76. EP260214a: VLT near-infrared observation
  77. EP260214b: SVOM/VT optical observation
  78. EP260214a: NOT optical upper limits
  79. EP260214a: COLIBRÍ optical upper limits
  80. EP260214b: OHP/T120 optical observations
  81. EP260214a: refined analysis of the EP-FXT observation
  82. EP260214b: LCO optical counterpart detection
  83. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  84. GRB 260211A: SVOM/VT optical counterpart
  85. EP260214b: COLIBRÍ optical observations
  86. EP260214a: SVOM/VT optical upper limits
  87. EP260214b: NOT optical counterpart detection
  88. EP260214b: Einstein Probe detection of a fast X-ray transient
  89. EP260214a: Global MASTER-Net observations report
  90. EP260214a: Einstein Probe detection of an X-ray transient
  91. GRB 260212A: AstroSat CZTI detection
  92. GRB 260212A: Fermi GBM Observation
  93. EP260213a: Liverpool Telescope optical upper limits
  94. EP260213a: Global MASTER-Net observations report
  95. EP260213a: COLIBRÍ optical upper limits
  96. GRB 260212A: GECAM-B observation
  97. EP260213a: Optical upper limits with Kinder observations
  98. EP260213a: SVOM/VT optical upper limit
  99. EP260213a: Mondy R-band optical upper limit
  100. EP260213a: NUTTelA-TAO Early Optical Limits

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