Skip to main content
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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"

26331 results found.

  1. GRB 251201B: Kilonova-Catcher optical afterglow detection
  2. GRB 251201B: Swift/UVOT Detection
  3. GRB 251130B: Glowbug gamma-ray detection
  4. EP251130a: continued NOT optical observations indicate steep fading phase
  5. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  6. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  7. GRB 251126A: SAO RAS optical marginal detection
  8. GRB 251202A: Swift-XRT afterglow detection
  9. EP251129a/GRB 251129A: NOWT Detection
  10. GRB 251126A: SVOM/VT optical observation
  11. EP251130a: SVOM/VT optical observation
  12. Fermi GRB 251202A: Global MASTER-Net observations report
  13. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  14. GRB 251201B: Swift-XRT refined Analysis
  15. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  16. GRB 251201A: SVOM/GRM observation of a burst
  17. GRB 251201B: SVOM/VT optical fading
  18. Swift GRB 251201B : MASTER optical counterpart detection
  19. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  20. Swift GRB 251201B: Global MASTER-Net observations report
  21. GRB 251201B: Enhanced Swift-XRT position
  22. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  23. GRB 251201B: Swift detection of a burst with an optical counterpart
  24. GRB 251201B: Fermi GBM Final Real-time Localization
  25. EP251130a: Mondy optical observations
  26. EP251130a: Optical detections with Kinder observations
  27. SVOM GRB251201.19: Global MASTER-Net observations report
  28. EP251130a: SAO RAS optical observations
  29. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  30. EP251130A: Optical observation from 1.3m DFOT
  31. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  32. EP251130a: JinShan optical observations
  33. GRB 251201A: MAXI/GSC detection
  34. Fermi GRB 251130B: Global MASTER-Net observations report
  35. GRB 251127A: SVOM/GRM observation
  36. IceCube Alert 251130.75: Global MASTER-Net observations report
  37. EP251130a: Swift-XRT counterpart detection
  38. EP251130a: Global MASTER-Net observations report
  39. EP251130a: COLIBRÍ optical counterpart candidate
  40. EP251130a: Einstein Probe detection of an X-ray transient
  41. GRB 251129A / EP251129a: SAO RAS optical observations
  42. GRB 251126A: SAO RAS optical observations
  43. GRB 251128A: SVOM/GRM observation of a long burst
  44. SVOM GRB 251129A : MASTER optical counterpart detection
  45. GRB 251129A: Swift-XRT afterglow detection
  46. EP251129a: Global MASTER-Net observations report
  47. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  48. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  49. GRB 251128A: Fermi GBM Observation
  50. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  51. GRB 251129A: SVOM detection of a burst
  52. SVOM GRB251129A: Global MASTER-Net observations report
  53. GRB 251129A: SVOM detection of a burst
  54. GRB 251126A: Swift-BAT refined analysis
  55. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  56. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  57. Fermi GRB 251128A: Global MASTER-Net observations report
  58. GRB 251127A: Glowbug gamma-ray detection
  59. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  60. GRB 251126A: further SAO RAS optical observations
  61. GRB 251126A NUTTelA-TAO Early Measurements
  62. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  63. GRB251126A: MAO/AZT-22 optical observations
  64. GRB251126A: Continued optical observation from 1.3m DFOT
  65. GRB 251126A: Swift/UVOT Detection
  66. GRB 251126A: Mondy and SAO RAS optical observations
  67. GRB 251126A: Swift-XRT refined Analysis
  68. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  69. GRB 251126A: NOT optical observations
  70. GRB 251126A: 1.3m DFOT optical afterglow detection
  71. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  72. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  73. Fermi GRB 251127A: Global MASTER-Net observations report
  74. GRB 251126A: Enhanced Swift-XRT position
  75. GRB 251126A: Kilonova-Catcher optical afterglow detection
  76. GRB 251126A: Nanshan/HMT optical afterglow detection
  77. Swift GRB 251126A: Global MASTER-Net observations report
  78. GRB 251121A: Fermi GBM Observation
  79. GRB 251126A: GIT discovery of the likely optical afterglow
  80. GRB 251126A: Swift detection of a burst
  81. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  82. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  83. EP251124b: NOT r- and z-band optical upper limits
  84. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  85. Fermi GRB 251125B: Global MASTER-Net observations report
  86. EP251124b: Global MASTER-Net observations report
  87. EP251124b: EP-WXT detection of a fast X-ray transient
  88. EP251124a: Xinglong GWAC-F60A optical observation
  89. Fermi GRB 251125A: Global MASTER-Net observations report
  90. EP251124a: NOT r- and z-band optical upper limits
  91. EP251124a: Global MASTER-Net observations report
  92. EP251124a: Swift-XRT observations
  93. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  94. EP251124a: Optical upper limit with Kinder observations
  95. Fermi GRB 251124a: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  97. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  98. EP251124a: GROWTH-India Telescope optical upper limits
  99. EP251124a: Einstein Probe detection of an X-ray transient
  100. GRB 251116C: Swift-XRT confirmation of fading

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