Skip to main content
New! BOOM Notices and Schema v7.0.0. 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"
  1. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  2. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  3. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  4. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  5. GRB 251002A: EP-FXT counterpart detection
  6. GRB 251003A: LCOGT Optical Detection
  7. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  8. GRB 251003A: 1.5m OSN afterglow candidate
  9. GRB 251003A: Prompt enhanced Swift-XRT position
  10. GRB 251003A: Swift detection of a burst
  11. GRB 251003A: Fermi GBM Final Real-time Localization
  12. Swift GRB251003A: Global MASTER-Net observations report
  13. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  14. GRB 251002A: BOOTES-6 early optical detection
  15. GRB 251002A: SAO RAS optical observations
  16. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  17. GRB 251002A: FRAM-ORM afterglow detection
  18. GRB 251002A: LCO optical observation
  19. GRB 251002A: SVOM/VT optical observation
  20. GRB 251002A: SVOM detection of a burst
  21. Fermi GRB 251002A: Global MASTER-Net observations report
  22. GRB 251001B: Swift-BAT refined analysis
  23. GRB 251001A: SVOM/GRM observation
  24. GRB 251001A: Insight-HXMT detection
  25. GRB 251001B: Swift/UVOT Detection
  26. GRB 251001B: COLIBRÍ optical observations
  27. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  28. GRB 251001B: Swift-XRT refined Analysis
  29. GRB 251001B: SVOM/VT optical observation
  30. GRB 251001B: NOT optical observations
  31. GRB 251001C: Glowbug gamma-ray detection
  32. Swift GRB 251001B: Global MASTER-Net observations report
  33. GRB 251001B: Fermi GBM Observation
  34. GRB 251001B: Further GOTO observations of optical counterpart.
  35. GRB 251001B: Enhanced Swift-XRT position
  36. GRB 250930A: Fermi GBM Final Localization
  37. GRB 251001B: LCOGT Optical Observations
  38. GRB 250930A: SVOM/GRM observation
  39. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  40. GRB 251001B: GOTO optical counterpart detection
  41. GRB 251001B: Swift detection of a burst
  42. GRB 251001B: Fermi GBM Final Real-time Localization
  43. GRB 251001A: Fermi GBM Detection
  44. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  45. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  46. GRB 251001A: Fermi GBM Final Real-time Localization
  47. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  48. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  49. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  50. GRB 250925A: MAO/AZT-22 optical observations
  51. Fermi GRB 250929A: Global MASTER-Net observations report
  52. GRB 250929A: Fermi GBM Final Real-time Localization
  53. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  54. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  55. GRB 250925A: Mondy I-band optical observations
  56. GRB 250916A: SVOM/VT optical observation
  57. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  59. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  60. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  61. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  62. GRB 250924A: SVOM/GRM observation
  63. GRB 250925A: Swift-XRT refined Analysis
  64. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  65. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  66. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 250926A: Insight-HXMT detection
  68. GRB 250926B: Fermi GBM Final Localization
  69. Fermi trigger No 780609036: Global MASTER-Net observations report
  70. IceCube Alert 250926.52: Global MASTER-Net observations report
  71. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  72. GRB 250926A: AstroSat CZTI detection
  73. GRB 250925A: Swift/UVOT Upper Limits
  74. GRB 250925A: Swift-BAT refined analysis
  75. GRB 250925A: Mondy and AbAO optical observations
  76. GRB 250925A: COLIBRÍ photometric redshift
  77. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  78. GRB 250925A: SVOM/GWAC-F60A upper limit
  79. GRB 250925A/EP250925a: EP-WXT detection
  80. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  81. GRB 250925A : MITSuME Akeno optical upper limits
  82. GRB 250925A: JinShan optical observations
  83. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  84. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  85. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  86. Fermi GRB 250926A: Global MASTER-Net observations report
  87. GRB 250926A: Fermi GBM Final Real-time Localization
  88. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  89. GRB250925A: Liverpool Telescope optical observations
  90. GRB 250925A: NOT optical afterglow candidate
  91. GRB 250925A: Leavitt Observatory optical upper limit
  92. GRB 250925A: Enhanced Swift-XRT position
  93. GRB 250924A: Swift-BAT refined analysis
  94. GRB 250925A: GROWTH-India Telescope Upper Limits
  95. GRB 250925A: Swift detection of a burst
  96. Swift GRB 250925A: Global MASTER-Net observations report
  97. GRB 250922A: SVOM/GRM observation
  98. GRB 250924A: 1.6m Mephisto optical upper limits
  99. GRB 250924A: SAO RAS optical observations
  100. GRB 250924A: NOT optical observations

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