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. GRB 251115A: Fermi GBM Observation
  2. The EP-WXT trigger 01709248635 is likely a flaring star
  3. GRB 251121A: Fermi GBM Final Real-time Localization
  4. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  5. Fermi trigger No 785388351: Global MASTER-Net observations report
  6. EP251118A: 1.3m DFOT optical afterglow detection
  7. GRB 251118A: Swift/UVOT Detection
  8. EP251118a / GRB 251118C: SAO RAS optical observations
  9. GRB 251118A: Glowbug gamma-ray detection
  10. GRB 251118A: Fermi GBM Observation
  11. GRB 251118A: Swift-XRT afterglow detection
  12. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  13. EP251118a: Optical detection with Kinder observations
  14. GRB 251118A: GECAM-B detection
  15. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  16. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  17. EP251118a / GRB 251118C: SVOM/VT optical observation
  18. The EP-WXT trigger 01709248403 is likely a flaring star
  19. GRB 251118A: NuSTAR detection of bright prompt emission
  20. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  21. GRB 251116C: NOT optical observations
  22. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  23. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  24. GRB 251018A: FRAM-Auger optical detection
  25. GRB 251117A: Swift-XRT observations
  26. EP251118A / GRB 251118C : MASTER optical counterpart observations
  27. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  28. Konus-Wind detection of GRB 251118C (EP251118a)
  29. The EP-WXT trigger 01709248388 is likely a flaring star
  30. EP251118a: FTW optical and NIR observations
  31. GRB 251117A: Insight-HXMT/HE detection
  32. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  33. EP251118a: VLT near-infrared observation
  34. GRB 251116D: SVOM/GRM observation of a long GRB
  35. EP251118a: GOTO optical afterglow detection
  36. GRB 251119A: SVOM detection of a possible burst
  37. EP251118a: NOT spectroscopic redshift of z = 1.216
  38. EP251118a: Global MASTER-Net observations report
  39. EP251118a: preliminary result of EP-FXT follow-up observation
  40. LAT GRB251118.86: Global MASTER-Net observations report
  41. GRB 251118A: Fermi-LAT detection
  42. EP251118a: NOT candidate optical counterpart
  43. GRB 251118A: Swift ToO observations
  44. EP251118a: Einstein Probe detected of a fast X-ray transient
  45. Fermi GRB 251118B: Global MASTER-Net observations report
  46. GRB 251118B: Fermi GBM Final Real-time Localization
  47. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  48. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  49. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  50. GRB 251118A: Fermi GBM Final Real-time Localization
  51. GRB 251116C: SVOM/ECLAIRs refined analysis
  52. GRB 251116B: SVOM/ECLAIRs refined analysis
  53. GRB 251117A: AstroSat CZTI detection
  54. GRB 251114B: Insight-HXMT/HE detection
  55. GRB 251114B: GECAM-B detection of a short burst
  56. GRB 251117A: Fermi GBM observation
  57. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  58. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  59. GRB 251116D: Insight-HXMT/HE detection
  60. GRB 251115A: Swift-XRT observations
  61. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  62. GRB 251117A: SVOM/GRM observation of a short burst
  63. GRB 251117A: Tiled Swift observations
  64. GRB 251117A: Fermi-LAT detection
  65. LAT GRB251117.51: Global MASTER-Net observations report
  66. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  67. GRB 251116C: Swift/BAT arcminute localization of a burst
  68. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  69. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  70. GRB 251116B: SVOM/VT optical upper limit
  71. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  72. GRB 251116C: Swift-XRT observations
  73. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  74. GRB 251117A: Fermi GBM Final Localization Correction
  75. GRB 251116D: Glowbug gamma-ray detection
  76. EP251023a: Assy AZT-20 optical observations
  77. EP251023a: UAFO and AbAO optical observations
  78. GRB 251116D: AstroSat CZTI detection
  79. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  80. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  81. GRB 251116C: SVOM/VT optical upper limit
  82. GRB 251025B: further Mondy optical observations
  83. GRB 251111A: Mondy optical upper limit
  84. GRB 251116B: EP-FXT follow-up observation
  85. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  87. GRB 251116B: LCO optical upper limits
  88. GRB 251116C: LCO optical upper limits
  89. SVOM GRB251116C: Global MASTER-Net observations report
  90. GRB 251116C: SVOM detection of a burst
  91. GRB 251116B: SVOM detection of a burst
  92. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  93. GRB 251116A: Fermi GBM Final Real-time Localization
  94. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  95. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  96. GRB 251115A: Tiled Swift observations
  97. GRB 251115A: Fermi-LAT detection
  98. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  99. Fermi GRB 251115A: Global MASTER-Net observations report
  100. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume

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