Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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 241026A: Fermi GBM Final Real-time Localization
  2. GRB241025A: 1.3m DFOT optical afterglow detection
  3. EP241021a: optical follow-up observations with Xinglong Observatory
  4. ​GRB 241025A: optical photometry from Konkoly
  5. GRB 241025A: GROWTH-India Telescope optical observations
  6. GRB 241025A: COLIBRÍ Detection of the Afterglow
  7. GRB 241025A: Swift-XRT refined Analysis
  8. GRB 241025C: Fermi GBM Detection
  9. GRB 241025A: Fermi GBM Observation
  10. IPN triangulation of GRB 241022A (short/hard)
  11. LIGO/Virgo/KAGRA S241009l: Upper limits from Swift/BAT-GUANO
  12. GRB 241025C: Fermi GBM Final Localization
  13. GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
  14. GRB 241025B: Fermi GBM Final Localization
  15. Fermi trigger No 751563375: Global MASTER-Net observations report
  16. Fermi trigger No 751554401: Global MASTER-Net observations report
  17. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  18. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  19. EP 241021a: Swift-XRT observations
  20. EP241021a: optical follow-up observations with the Liverpool Telescope
  21. Fermi GRB 241025A: Global MASTER-Net observations report
  22. Swift GRB 241025A: Global MASTER-Net observations report
  23. EP241025a (GRB 241025A): EP observations update
  24. GRB 241025A : SVOM/VT optical afterglow observations
  25. EP 241021A: Swift ToO observations
  26. EP241021a: Liverpool Telescope optical follow-up observations
  27. GRB 241025A: Enhanced Swift-XRT position
  28. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  29. GRB 241025A: NOT spectroscopic redshift of z = 4.20
  30. GRB 241025A: DDOTI Afterglow detection
  31. EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
  32. GRB 241025A: SVOM/GRM observation
  33. GRB 241025A: TRT optical afterglow observation
  34. Fermi GRB 241024B: Global MASTER-Net observations report
  35. GRB 241025A: Fermi GBM Final Real-time Localization
  36. GRB 241025A: Swift detection of a burst with an optical counterpart
  37. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  38. GRB 241001A: ATCA radio observations
  39. GRB 241024B: Fermi GBM Final Localization
  40. EP241021a: No Detection in Fermi-GBM Observation
  41. GRB 241010A: VIRT Optical Upper Limit
  42. GRB 241024A: Fermi GBM Final Localisation
  43. EP241021a: VLT/FORS2 redshift z = 0.75
  44. Fermi trigger No 751449953: Global MASTER-Net observations report
  45. EP241021a: SAO RAS optical observations
  46. EP241021a: KAIT optical observations
  47. EP241021a: EP-FXT follow-up observation update
  48. IPN triangulation of GRB 241021A (long)
  49. EP241021a: Optical counterpart observations with the Liverpool Telescope
  50. EP241021a: 1.3m DFOT Optical observations
  51. EP241021a: GSP detects optical candidate counterpart
  52. EP241021a: Optical upper limits with Kinder observations
  53. EP241021a: TRT optical observations
  54. GRB 241018A: SVOM/C-GFT optical observations
  55. EP241021a: NOT likely optical counterpart
  56. EP EP241021a: Global MASTER-Net observations report
  57. GRB241017A: 1.3m DFOT optical upper limit
  58. GRB 241018A: 1.3m DFOT Optical upper limit
  59. GRB 241018A: EP-FXT afterglow detection
  60. EP241021a: GOTO optical upper limits
  61. EP241021a: EP detection of a fast X-ray transient
  62. IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
  63. Konus-Wind detection of GRB 241018A
  64. GRB 241018A: SVOM/GRM observation
  65. GRB 241018A/sb24101802: Mephisto optical upper limit
  66. GRB 241017A/sb24101702: Mephisto optical upper limit
  67. GRB 241018A: BOOTES-4/MET optical upper limit
  68. GRB 241018A: Mondy optical upper limit
  69. GRB 241018A: SVOM/VT further analysis and counterpart confirmed
  70. GRB 241018A: GROWTH-India telescope optical upper limit
  71. GRB241018A: XingLong Optical Upper Limit
  72. GRB 241018A: Swift-XRT observations
  73. GRB 241018A: REM optical/NIR upper limits
  74. GRB 241018A: NOT optical observations
  75. GRB 241017A: SVOM/VT follow-up and optical upper limit
  76. GRB 241018A: SVOM/VT follow-up and optical candidate
  77. GRB 241018A: LCO/0.4m optical upper limits
  78. GRB 241018A: Swift ToO observations
  79. GRB 241006A: VIRT Optical Upper Limit
  80. GRB 240727A: VIRT Optical Upper Limit
  81. GRB 241018A: X-ray afterglow candidate observed by MXT
  82. GRB 241016B: Fermi GBM Observations
  83. GRB 241018A: Detection of a bright long GRB by SVOM
  84. GRB 241017A: Swift-XRT observations
  85. GRB241017a: Liverpool Telescope observations of XRT uncatalogued sources
  86. GRB 241001A: EP-FXT afterglow detection
  87. GRB 241017A: GROWTH-India Telescope optical upper limit
  88. GRB241017A: TOO Observations by SVOM/MXT
  89. GRB 241016B: Swift/BAT-GUANO localization skymap of a short burst
  90. GRB 241017A: J-band upper limit from WINTER
  91. Fermi trigger No 750788395: Global MASTER-Net observations report
  92. GRB 241016B: SVOM/GRM observation
  93. GRB241016C: Fermi GBM Final Localization
  94. Fermi Gamma-ray Burst Monitor trigger 750792698/241016730 is not a GRB
  95. GRB 241017A: Swift ToO observations
  96. GRB 241017A : Detection of a weak and soft long duration GRB by SVOM/ECLAIRs
  97. Fermi GRB 241016B: Global MASTER-Net observations report
  98. GRB 241016B: Fermi GBM Final Localization
  99. Fermi GRB 241016A: Global MASTER-Net observations report
  100. GRB 241016A: Fermi GBM Final Real-time Localization

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