Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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. LIGO/Virgo S191110af: No counterpart candidates in Fermi-LAT observations
  2. LIGO/Virgo S191110af: upper limits from AGILE/MCAL observations
  3. LIGO/Virgo S191110af: Evryscope observation report, no counterpart candidates
  4. GRB 191111A: Fermi GBM Final Real-time Localization
  5. LIGO/Virgo S191110af: No counterpart candidates in INTEGRAL SPI-ACS, prompt observation
  6. LIGO/Virgo S191110af: Upper limits from Fermi-GBM Observations
  7. LIGO/Virgo S191110af: Coverage and upper limits from MAXI/GSC observations
  8. LIGO/Virgo S191110af: Identification of a GW unmodeled transient candidate
  9. LIGO/Virgo S191110af: Upper limits from IceCube neutrino searches
  10. LIGO/Virgo S191110af: Global MASTER-Net observations report
  11. LIGO/Virgo S191109d: No significant candidates in FRAM-TAROT-GRANDMA observations
  12. LIGO/Virgo S191110x: Retraction of GW compact binary merger candidate
  13. LIGO/Virgo S191110x: Global MASTER-Net observations report
  14. LIGO/Virgo S191109d: No counterpart candidates in Fermi-LAT observations
  15. LIGO/Virgo S191105e: No significant candidates in FRAM-TAROT-GRANDMA observations
  16. GRB 191110A: Fermi GBM Final Real-time Localization
  17. LIGO/Virgo S191105e: Upper limits from Insight-HXMT/HE observations
  18. LIGO/Virgo S191109d: AstroSat CZTI upper limits
  19. LIGO/Virgo S191109d: no counterpart candidates in the Swift/BAT observations
  20. LIGO/Virgo S191109d : no neutrino counterpart candidate in ANTARES search
  21. LIGO/Virgo S191109d: Global MASTER-Net observations report
  22. LIGO/Virgo S191109d: upper limits from AGILE-GRID observations mailed-by:
  23. LIGO/Virgo S191109d: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation
  24. LIGO/Virgo S191109d: upper limits from AGILE/MCAL observations
  25. LIGO/Virgo S191109d: Upper limits from Fermi-GBM Observations
  26. LIGO/Virgo S191109d: Coverage and upper limits from MAXI/GSC observations
  27. LIGO/Virgo S191109d: Upper limits from IceCube neutrino searches
  28. LIGO/Virgo S191109d: Identification of a GW compact binary merger candidate
  29. GRB 191106A: AstroSat CZTI detection
  30. GRB 191108A: Fermi GBM Final Real-time Localization
  31. GRB 191106A: Swift/UVOT Upper Limits
  32. GRB 191106A: Swift-BAT refined analysis
  33. ZTF19abvizsw: Upper limits from Konus-Wind observations
  34. LIGO/Virgo S191105e: AstroSat CZTI upper limits
  35. LIGO/Virgo S191105e: Not observable by CALET
  36. LIGO/Virgo S191105e: No counterpart candidates in Fermi-LAT observations
  37. LIGO/Virgo S191105e: Coverage and upper limits from MAXI/GSC observations
  38. LIGO/Virgo S191105e: no counterpart candidates in the Swift/BAT observations
  39. GRB 191106A: NOT optical upper limit
  40. GRB 191106A: Swift-XRT refined Analysis
  41. LIGO/Virgo S191105e : no neutrino counterpart candidate in ANTARES search
  42. LIGO/Virgo S191105e: No counterpart candidates in HAWC observations
  43. LIGO/Virgo S191105e: No counterpart candidates in INTEGRAL SPI-ACS and,IBIS prompt observation
  44. LIGO/Virgo S191105e: upper limits from AGILE/GRID observations
  45. LIGO/Virgo S191105e: Upper limits from Fermi-GBM Observations
  46. LIGO/Virgo S191105e: Global MASTER-Net observations report
  47. LIGO/Virgo S191105e: upper limits from AGILE/MCAL observations
  48. LIGO/Virgo S191105e: Identification of a GW compact binary merger candidate
  49. LIGO/Virgo S191105e: Upper limits from IceCube neutrino searches
  50. GRB 191106A: Mondy optical upper limit
  51. GRB 191106A: BOOTES-4/MET optical limit
  52. GRB 191106A: MASTER optical observation
  53. GRB 191106A: Swift detection of a burst
  54. GRB191016A GROND observations
  55. GRB 191031D: Chandra upper limit
  56. Swift trigger 933276 MASTER observation
  57. Fermi trigger No 594592184: Global MASTER-Net observations report
  58. Fermi trigger No 594523229: Global MASTER-Net observations report
  59. Trigger 933285: Swift detection of the brightest burst so far from SGR 1935+2154
  60. Swift GRB191105.01: Global MASTER-Net observations report
  61. Trigger 933276: Swift detection of further activity from SGR 1935+2154
  62. Swift GRB191105.01: Global MASTER-Net OT detection
  63. GRB 191101A: Swift-BAT refined analysis
  64. Fermi GBM GRB 191104C (trigger 594592184 / 191104854) is not a GRB
  65. GRB 191104C: Fermi GBM Final Real-time Localization
  66. GRB 191101A: Swift/UVOT Upper Limits
  67. Fermi GBM GRBs 191104 A, B, C and triggers 594534420/191104185 and 594563923/191104527 are not GRBs
  68. SGR 1935+2154: Swift-BAT refined analysis
  69. Fermi trigger No 594563923: Global MASTER-Net observations report
  70. GRB 191104B/GRB 191104C are SGR 1935+2154
  71. Fermi trigger No 594557071: Global MASTER-Net observations report
  72. GRB 191104C: BALROG localization (Fermi Trigger 594557071 / GRB 191104448)
  73. GRB 191104C: Fermi GBM Final Real-time Localization
  74. Fermi trigger No 594551878: Global MASTER-Net observations report
  75. Fermi trigger No 594528816: Global MASTER-Net observations report
  76. GRB 191104B: Fermi GBM Final Real-time Localization
  77. Trigger 933083: Swift detection of SGR 1935+2154
  78. Fermi GBM triggers 594523229/191104056 and 594528816/191104120 are not GRBs
  79. GRB 191104A: Fermi GBM Final Real-time Localization
  80. GRB 191031D: Zwicky Transient Facility Follow-Up of a Swift Short GRB (Trigger 594249816/191031891)
  81. Konus-Wind observation of GRB 191031D: correction to GCN 26126
  82. GRB 191031E: Insight-HXMT/HE detection
  83. GRB 191031D: Gemini optical upper limit
  84. GRB 191031C: Insight-HXMT/HE detection
  85. GRB 191101A: iTelescope optical limit
  86. GRB 191101A: Swift-XRT refined Analysis
  87. Baksan Neutrino Observatory Alert 191102.06: Global MASTER-Net observations report
  88. GRB 191101A: VIRT Optical Upper Limits
  89. Fermi trigger No 594336535: Global MASTER-Net observations report
  90. GRB 191101A: Enhanced Swift-XRT position
  91. Swift GRB191101.88: Global MASTER-Net observations report
  92. Fermi trigger No 594227699: Global MASTER-Net observations report
  93. GRB 191101A: Prompt enhanced Swift-XRT position
  94. GRB 191101B: Fermi GBM Final Real-time Localization
  95. GRB 191101A: Swift detection of a burst
  96. GRB 191031D: MMT Binospec Optical Upper Limit
  97. GRB 191031D: Swift-BAT refined analysis
  98. GRB 191031C: Swift-BAT refined analysis
  99. GRB 191031A: Swift-BAT refined analysis
  100. GRB 191031C: Swift-XRT refined Analysis

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