Skip to main content
Circulars over Kafka event name backfill. 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').

18304 results found.

  1. GRB 250407A: LCO detection of a fading optical counterpart
  2. EP250407a: Swift-XRT observations
  3. Konus-Wind detection of GRB 250407A
  4. GRB 250407A: SVOM/GRM observation of a bright long burst
  5. GRB 250407A: EP-WXT afterglow detection
  6. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  7. GRB 250407A: Fermi GBM Detection
  8. GRB 250407A: Swift-XRT afterglow detection
  9. GRB 250407A: Swift ToO observations
  10. GRB 250407A: SRG/ART-XC afterglow detection
  11. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  12. IPN triangulation of GRB 250406B (short/hard)
  13. GRB 250331D: Swift-XRT afterglow detection
  14. GRB 250403A: Montarrenti Observatory optical detection
  15. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  16. GRB 250331C Swift-BAT refined analysis
  17. GRB 250331B Swift-BAT refined analysis
  18. GRB 250330A Swift-BAT refined analysis
  19. EP250321A: J band upper limit by SYSU 80cm telescope
  20. GRB 250403A: Swift/UVOT Detection
  21. GRB 250402A: Swift/UVOT Upper Limits
  22. GRB 250403A: LCO optical counterpart detection
  23. GRB 250402A: EP-FXT afterglow detection
  24. GRB 250403A: Swift-XRT observations
  25. GRB 250402A: Swift-XRT observations
  26. GRB 250225B: VLT host galaxy redshift z = 0.950
  27. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  28. GRB 250329B: Swift/UVOT Upper Limit
  29. GRB 250329A: Swift/UVOT Upper Limit
  30. GRB 250327B: Swift/UVOT Detection
  31. GRB 250327A: Swift/UVOT Upper Limits
  32. GRB250331D: AbAO optical observations
  33. GRB 250331D: Fermi GBM observation
  34. GRB 250331C: Swift/UVOT Upper Limits
  35. GRB 250331B: Swift/UVOT Upper Limits
  36. GRB 250331D: Swift-XRT observations
  37. GRB 250331C: Swift-XRT refined Analysis
  38. GRB 250331B: Swift-XRT refined Analysis
  39. GRB 250331B: Swift-XRT refined Analysis
  40. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  41. GRB 250327A Swift-BAT refined analysis
  42. GRB 250329B: CAHA 2.2m telescope optical limit
  43. GRB 250331D: Swift ToO observations
  44. Swift GRB 250331C: Global MASTER-Net observations report
  45. Swift GRB 250331B: Global MASTER-Net observations report
  46. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  47. GRB 250331C: Enhanced Swift-XRT position
  48. GRB 250331B: Enhanced Swift-XRT position
  49. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  50. GRB 250329B: Swift-XRT confirmation of fading
  51. GRB20250327B: 45th Parallel Observatory upper limit
  52. GRB 250328A: Swift/UVOT Detection
  53. GRB 250328A: Swift-XRT refined Analysis
  54. GRB 250330A: Fermi GBM Observation
  55. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  56. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  57. GRB 250331C: Prompt enhanced Swift-XRT position
  58. GRB 250331C: Swift detection of a burst
  59. GRB 250331B: Swift detection of a burst
  60. GRB 250330A: SVOM/VT optical upper limit
  61. GRB 250330A: BOOTES-7 early optical upper limit
  62. GRB 250330A: Swift/UVOT Upper Limits
  63. GRB 250330A: Swift-XRT afterglow detection
  64. GRB 250330A: Fermi GBM Final Localization
  65. GRB 250330A: Prompt Swift-XRT position
  66. GRB 250329B: Swift-XRT afterglow detection
  67. GRB 250330A: Swift detection of a burst
  68. Swift GRB250330.26: Global MASTER-Net observations report
  69. GRB 250329B: SVOM/C-GFT optical upper limit
  70. GRB 250329B: SVOM/VT optical upper limit
  71. GRB 250329A: Swift-XRT afterglow detection
  72. GRB 250328A: SVOM/C-GFT optical upper limit
  73. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  74. GRB 250327B: LCO optical counterpart detection
  75. GRB 250322A: GRANDMA/TNOT optical upper limits
  76. GRB 250327A: SVOM/VT upper limits on the XRT position
  77. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  78. GRB 250327A: Swift-XRT refined Analysis
  79. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  80. GRB 250327A: J-band observations with WINTER
  81. GRB 250327A: SVOM/VT optical candidate
  82. GRB 250327A: Fermi GBM observation
  83. Swift GRB 250327A: Global MASTER-Net observations report
  84. GRB 250327A: DDOTI Optical Observations
  85. GRB 250327A: COLIBRÍ optical upper limit
  86. GRB 250327A: Swift detection of a burst
  87. Konus-Wind detection of GRB 250322A (short)
  88. IPN triangulation of GRB 250322B
  89. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  90. GRB 250322A: Swift-BAT refined analysis
  91. GRB 250322A: Swift/UVOT Upper Limits
  92. GRB 250321B: Swift-XRT observations
  93. GRB 250322A: Swift-XRT refined Analysis
  94. GRB 250322A: AstroSat CZTI detection of a short burst
  95. GRB250322A: STEP/T80S optical limits
  96. GRB 250322A: VLT optical observations
  97. GRB 250322A: VLT near-infrared observations
  98. GRB 250322A: NOT optical upper limits
  99. GRB 250322A: Enhanced Swift-XRT position
  100. GRB 250322A: MASTER optical observation

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