Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

3360 results found.

  1. GRB 250617B: SAO RAS optical observations
  2. Fermi trigger No 771752663: Global MASTER-Net observations report
  3. Fermi trigger No 771424081: Global MASTER-Net observations report
  4. EP250612a: Einstein Probe detection of an X-ray transient
  5. Swift GRB250612.04: Global MASTER-Net observations report
  6. Fermi trigger No 771072240: Global MASTER-Net observations report
  7. GRB 250527C: CrAO Optical Upper Limit
  8. GRB 250606A: Fermi GBM Final Real-time Localization
  9. Fermi trigger No 770867684: Global MASTER-Net observations report
  10. GRB 250605A: LT optical observations
  11. Fermi GRB 250531A: Global MASTER-Net observations report
  12. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  13. Fermi trigger No 770058372: Global MASTER-Net observations report
  14. GRB 250314A: CIDER NB1008 upper limit
  15. EP250526a: Einstein Probe detection of a fast X-ray transient
  16. Fermi GRB 250516A: Global MASTER-Net observations report
  17. Konus-Wind detection of GRB 250506A
  18. EP250511a: COLIBRÍ optical counterpart candidate
  19. Fermi GRB 250510C: Global MASTER-Net observations report
  20. Fermi GRB 250510B: Global MASTER-Net observations report
  21. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  22. GRB 250506A: Swift-XRT observations
  23. Fermi GRB 250504A: Global MASTER-Net observations report
  24. Fermi trigger No 767975731: Global MASTER-Net observations report
  25. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  26. EP250428b: SAO RAS optical upper limit
  27. EP250427a / GRB 250427A: OHP/T193 photometric observations
  28. EP250427a: Lesedi optical counterpart detection
  29. EP250427A: COLIBRÍ Continuing Optical Observations
  30. EP250427a: LT optical counterpart detection
  31. EP250421a: Upper limits from Fermi-GBM Observations
  32. IceCube-250421A: DDOTI Detection of the LAST Candidate
  33. Fermi GRB 250421A: Global MASTER-Net observations report
  34. EP250421a: Einstein Probe detection of an X-ray transient
  35. IceCube Alert 250421.71: Global MASTER-Net observations report
  36. EP250416a: Global MASTER-Net observations report
  37. SVOM/sb25041603: SVOM detection of an X-ray transient
  38. EP250304a: ATCA radio observations
  39. Fermi trigger No 766148493: Global MASTER-Net observations report
  40. Fermi trigger No 766173972: Global MASTER-Net observations report
  41. Fermi GRB 250407A: Global MASTER-Net observations report
  42. IPN triangulation of GRB 250406B (short/hard)
  43. IceCube Alert 250406.95: Global MASTER-Net observations report
  44. Fermi trigger No 765619921: Global MASTER-Net observations report
  45. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  46. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  47. GRB 250404A / EP250404a: Mondy optical observations
  48. Fermi GRB 250404A: Global MASTER-Net observations report
  49. EP250404a: Global MASTER-Net observations report
  50. GRB 250327B: VIRT Optical Upper Limit
  51. GRB 250402A: Mondy optical observations
  52. Fermi GRB 250403A: Global MASTER-Net observations report
  53. GRB 250403A: GOTO optical counterpart follow-up observations
  54. GRB 250403A: GOTO detection of the optical afterglow
  55. GRB 250402A: REM optical/NIR upper limits
  56. GRB 250328A: AbAO AS-32 Optical Observations
  57. GRB 250322B possible detection by the AstroSat Satellite
  58. GRB 250331B: Swift detection of a burst
  59. GRB 250328A: 1.6m Mephisto optical observations
  60. IceCube Alert 250330.35: Global MASTER-Net observations report
  61. GRB 250327B: MASTER detection of OT rebrightening
  62. GRB 250327B: LCO optical counterpart detection
  63. FRB 20250316A: FTW optical observations
  64. GRB 250327B: further optical observations by LCOGT
  65. GRB 250327b: Liverpool Telescope optical observations
  66. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  67. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  68. GRB 250327B: SAO RAS optical candidate
  69. EP250321a: Xinglong 216 decaying optical observations
  70. GRB 250321B: SVOM detection of a sub-threshold transient event
  71. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  72. GRB 250317B: Mondy AZT-33IK Optical Observations
  73. Fermi trigger No 763933627: Global MASTER-Net observations report
  74. GRB 250314A: REM optical/NIR upper limits
  75. GRB 250317B: LCO detection of the fading optical afterglow
  76. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  77. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  78. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  79. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  80. Fermi GRB 250313A: Global MASTER-Net observations report
  81. Fermi GRB 250312B: Global MASTER-Net observations report
  82. GRB 241228A: VIRT Optical Upper Limit
  83. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  84. GRB 250228A: Fermi GBM Observation
  85. GRB 250225B: Swift-BAT refined analysis
  86. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  87. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  88. GRB 250309B / AT2025dws: SAO RAS optical observations
  89. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  90. IceCube Alert 250309.32: Global MASTER-Net observations report
  91. EP250308a: FTW optical and NIR upper limits
  92. GRB 250305A: AstroSat CZTI detection
  93. EP250302a:Xinglong optical observations
  94. Fermi trigger No 762963055: Global MASTER-Net observations report
  95. GRB 250305A: SVOM/GRM observation of a burst
  96. GRB 250305A: Fermi GBM Final Real-time Localization
  97. EP250302a: Mondy Continued Optical Observations
  98. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  99. EP250304a: Global MASTER-Net observations report
  100. GRB 250226A: GRANDMA Optical Observations

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