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. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  2. GRB 250702B: Late time Chandra observations
  3. EP250908b/EP#01709240653: Swift/UVOT Detection
  4. EP#01709240653: Swift-XRT observations
  5. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  6. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  8. EP250908c: SVOM/VT optical observation
  9. EP250908c: VLT/FORS2 optical counterpart identification
  10. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  11. EP250908b: SVOM/VT optical candidate
  12. The EP-WXT trigger EP250908a/01709240652 is not a real source
  13. EP250908c: Global MASTER-Net observations report
  14. Fermi GRB 250909A: Global MASTER-Net observations report
  15. EP250908c: Einstein Probe detection of an X-ray transient
  16. GRB 250909A: Fermi GBM Final Real-time Localization
  17. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  18. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  19. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  20. GRB 250907A: GECAM-B detection
  21. GRB 250905A: Swift-BAT refined analysis
  22. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  23. GRB 250903A: Swift-XRT afterglow detection
  24. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  25. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  26. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  27. EP250905a: Liverpool Telescope i-band upper limits
  28. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  29. EP250905b: EP-FXT follow-up observation
  30. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  31. EP250905a: Liverpool Telescope observations
  32. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  33. EP250905b: Global MASTER-Net observations report
  34. EP250905b: EP-WXT detection of a fast X-ray transient
  35. EP250905a: FTW one optical and multiple NIR counterpart candidates
  36. GRB 250905A: Swift-XRT refined Analysis
  37. EP250905a: JinShan likely optical counterpart detection
  38. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  39. GRB 250904A: Swift-BAT refined analysis
  40. IceCube Alert 250905.84: Global MASTER-Net observations report
  41. GRB 250905A: Swift/UVOT Upper Limits
  42. EP250905a: Global MASTER-Net observations report
  43. GRB 250901A - SVOM/ECLAIRs refined analysis
  44. EP250905a: Einstein Probe detection of an X-ray transient
  45. GRB 250905B: Fermi GBM Final Localization
  46. GRB250904A: Liverpool Telescope upper limits
  47. GRB 250905A: Enhanced Swift-XRT position
  48. GRB 250904A: Swift/UVOT Detection
  49. GRB 250903A: Swift/UVOT detection
  50. GRB 250904A: Swift-XRT refined Analysis
  51. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  52. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  53. EP detected a brightening of LMXB 1ES 1735-26.9
  54. GRB 250905A: KAIT optical upper limit
  55. GRB 250905A: Swift detection of a burst
  56. Swift GRB250905.09: Global MASTER-Net observations report
  57. Swift GRB 250904A: Global MASTER-Net observations report
  58. GRB 250904A: Enhanced Swift-XRT position
  59. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  60. GRB 250904A: TRT optical counterpart detection
  61. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  62. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  63. GRB 250904A: Prompt enhanced Swift-XRT position
  64. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  65. GRB 250904A: Swift detection of a burst
  66. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  67. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  68. GRB 250902A: VZLUSAT-2 detection
  69. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  70. GRB 250903A: Swift-XRT observations
  71. EP250903a: Swift-XRT observations
  72. EP#01709201209: Swift-XRT observations
  73. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  74. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  75. GRB 250830C: VZLUSAT-2 detection
  76. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  77. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  78. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  79. The EP-WXT trigger 01709201209 is likely a flaring star
  80. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  81. GRB 250903A: EP-FXT counterpart detection
  82. GRB 250902A: GECAM-B detection
  83. GRB 250903A: LCO optical observation
  84. GRB 250903A: LCO optical afterglow detection
  85. GRB 250903A: SVOM/VT optical confirmation with VHF data
  86. EP250903a: SVOM/VT optical confirmation
  87. EP250901a: Mondy, Assy and SAO RAS optical limits
  88. Subject GRB 250903A: SVOM/MXT afterglow detection
  89. EP250903a: LCO candidate counterpart discovery
  90. GRB 250903A: TRT optical counterpart detection
  91. GRB 250902B: AstroSat CZTI detection
  92. GRB 250903A: SVOM detection of a burst
  93. EP250903a: Global MASTER-Net observations report
  94. EP250903a: TRT optical observations
  95. EP250903a: Einstein Probe detection of an X-ray transient
  96. EP 250827B: Detection of supernova counterpart by LCO.
  97. EP/WXT01709201159: GOTO optical follow-up
  98. EP250827b / AT 2025wkm: TRT optical observations
  99. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  100. EP250827b: continued Liverpool Telescope 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