Skip to main content
Passing of Scott Barthelmy, GCN Founder 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 260223A: SVOM/VT optical observation
  2. GRB 260223A: SVOM/GRM observation
  3. GRB 260223A: COLIBRÍ further optical observations and a brightening
  4. EP260221a: Optical upper limit with Kinder observations
  5. GRB 260223A: COLIBRÍ optical observations
  6. GRB 260223A: DDOTI Optical Candidate
  7. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  8. Fermi GRB 260223A: Global MASTER-Net observations report
  9. GRB 260223A: Fermi GBM Final Real-time Localization
  10. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  11. EP260221a: COLIBRÍ optical counterpart candidate
  12. EP260221a: Gemini South z-band upper limit
  13. GRB 260222A: Fermi GBM Final Real-time Localization
  14. EP260221a: Global MASTER-Net observations report
  15. EP260221a: EP-FXT follow-up observation
  16. Fermi GRB 260221B: Global MASTER-Net observations report
  17. GRB 260221B: Fermi GBM Final Real-time Localization
  18. EP-WXT01709258519: Xinglong optical upper limit
  19. EP260221a: Xinglong optical upper limit
  20. Fermi GRB 260221A: Global MASTER-Net observations report
  21. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  22. GRB 260221A: Fermi GBM Final Real-time Localization
  23. EP260221a: GOTO optical upper limit
  24. EP260221a: COLIBRÍ optical upper limit
  25. SVOM alert sb26021801: LCO optical upper limit
  26. EP260221a: Einstein Probe detection of an X-ray transient
  27. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  28. GRB 260219A: AstroSat CZTI detection
  29. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 260219A: GECAM-B observation of a long burst
  31. Fermi GRB 260219A: Global MASTER-Net observations report
  32. GRB 260219A: Fermi GBM Final Real-time Localization
  33. SVOM alert sb26021801: LAST optical upper limit
  34. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. IceCube Alert 260217A: Global MASTER-Net observations report
  36. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  37. GRB 260217A: Fermi GBM Final Localization
  38. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  39. sb26021801: SVOM detection of a long faint X-ray transient
  40. The EP-WXT trigger 01709258455 is likely a flaring star
  41. EP-WXT 01709258455: NOT optical upper limits
  42. EP260214b: Mondy optical observations
  43. EP260214b: 1.3m DFOT optical upper limit
  44. EP260210a: Mondy optical upper limits
  45. Konus-Wind detection of GRB 260212A
  46. GRB 260208A: AbAO and Terskol optical upper limits
  47. GRB 260208A: continued Mondy optical observations
  48. IPN triangulation of GRB 260212A
  49. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 260213A: GECAM-B observation of a short burst
  51. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  52. GRB 260216A: Fermi GBM Final Real-time Localization
  53. EP260214b: Liverpool Telescope optical observations
  54. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  55. EP260214b: Optical upper limit with Kinder observations
  56. EP260214a: Optical upper limits with Kinder observations
  57. EP260214b: EP-FXT follow-up observation
  58. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  59. EP260214b: DDOTI Optical Detection
  60. EP260214b: GROWTH-India Telescope optical upper limit
  61. EP260214a: VLT near-infrared observation
  62. EP260214b: SVOM/VT optical observation
  63. EP260214a: NOT optical upper limits
  64. EP260214a: COLIBRÍ optical upper limits
  65. EP260214b: OHP/T120 optical observations
  66. EP260214a: refined analysis of the EP-FXT observation
  67. EP260214b: LCO optical counterpart detection
  68. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  69. GRB 260211A: SVOM/VT optical counterpart
  70. EP260214b: COLIBRÍ optical observations
  71. EP260214a: SVOM/VT optical upper limits
  72. EP260214b: NOT optical counterpart detection
  73. EP260214b: Einstein Probe detection of a fast X-ray transient
  74. EP260214a: Global MASTER-Net observations report
  75. EP260214a: Einstein Probe detection of an X-ray transient
  76. GRB 260212A: AstroSat CZTI detection
  77. GRB 260212A: Fermi GBM Observation
  78. EP260213a: Liverpool Telescope optical upper limits
  79. EP260213a: Global MASTER-Net observations report
  80. EP260213a: COLIBRÍ optical upper limits
  81. GRB 260212A: GECAM-B observation
  82. EP260213a: Optical upper limits with Kinder observations
  83. EP260213a: SVOM/VT optical upper limit
  84. EP260213a: Mondy R-band optical upper limit
  85. EP260213a: NUTTelA-TAO Early Optical Limits
  86. EP260213a: SVOM/C-GFT upper limit
  87. EP260213a: refined analysis of the EP-FXT observation
  88. EP260213a: Einstein Probe detection of a fast X-ray transient
  89. EP/WXT 01709258378: NOT optical upper limits
  90. GRB 260212A: SVOM/GRM observation of a long burst
  91. GRB 260213B: Fermi GBM Final Localization
  92. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  93. GRB 260211A - SVOM/ECLAIRs refined analysis
  94. GRB 260204A: SVOM/ECLAIRs refined analysis
  95. GRB 260213A: Fermi GBM Final Localization
  96. GRB 260211A: EP-FXT follow-up observation
  97. GRB 260211A: SVOM/VT optical observation
  98. GRB 260212A: Glowbug gamma-ray detection
  99. GRB 260211A: GOTO optical upper limit
  100. Fermi GRB 260212A: 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