Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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 250902A: CALET Gamma-Ray Burst Monitor detection
  2. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  3. GRB 250902A: VZLUSAT-2 detection
  4. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  5. GRB 250903A: Swift-XRT observations
  6. EP250903a: Swift-XRT observations
  7. EP#01709201209: Swift-XRT observations
  8. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  9. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  10. GRB 250830C: VZLUSAT-2 detection
  11. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  12. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  13. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  14. The EP-WXT trigger 01709201209 is likely a flaring star
  15. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  16. GRB 250903A: EP-FXT counterpart detection
  17. GRB 250902A: GECAM-B detection
  18. GRB 250903A: LCO optical observation
  19. GRB 250903A: LCO optical afterglow detection
  20. GRB 250903A: SVOM/VT optical confirmation with VHF data
  21. EP250903a: SVOM/VT optical confirmation
  22. EP250901a: Mondy, Assy and SAO RAS optical limits
  23. Subject GRB 250903A: SVOM/MXT afterglow detection
  24. EP250903a: LCO candidate counterpart discovery
  25. GRB 250903A: TRT optical counterpart detection
  26. GRB 250902B: AstroSat CZTI detection
  27. GRB 250903A: SVOM detection of a burst
  28. EP250903a: Global MASTER-Net observations report
  29. EP250903a: TRT optical observations
  30. EP250903a: Einstein Probe detection of an X-ray transient
  31. EP 250827B: Detection of supernova counterpart by LCO.
  32. EP/WXT01709201159: GOTO optical follow-up
  33. EP250827b / AT 2025wkm: TRT optical observations
  34. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  35. EP250827b: continued Liverpool Telescope observations
  36. GRB 250902B: SVOM/GRM observation
  37. EP250827b: SVOM/VT observation of AT 2025wkm
  38. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  39. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  40. Fermi GRB 250902B: Global MASTER-Net observations report
  41. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  42. GRB 250902A: Fermi GBM Detection
  43. GRB 250901A: Swift/UVOT Upper Limit
  44. GRB 250902B: Fermi GBM Final Real-time Localization
  45. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 250830B: Swift-XRT afterglow detection
  47. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  48. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  49. EP250827b: Liverpool Telescope observations
  50. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  51. GRB 250902A: SVOM/GRM observation
  52. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  53. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  54. GRB 250901A: EP-FXT follow-up observation
  55. GRB 250901A: NOT optical observations
  56. GRB 250902A: Fermi GBM Final Real-time Localization
  57. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB 250901A: SVOM/VT optical afterglow with VHF data
  59. GRB 250901A: Swift-XRT afterglow detection
  60. EP250901a: Swift-XRT observations
  61. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  62. GRB 250901A: LCO optical upper limit
  63. EP250827b: Swift observations of AT 2025wkm
  64. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  65. EP250827b: Gemini Spectroscopy of AT 2025wkm
  66. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  67. EP250831a: NOT optical observations and tentative afterglow candidate
  68. EP250827b: FTW Observations of AT 2025wkm
  69. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  70. GRB 250901A: SVOM detection of a burst
  71. GRB 250831B: SVOM/GRM observation
  72. GRB 250830C: Insight-HXMT detection
  73. EP250901a: Mephisto optical upper limits
  74. GRB 250830C: GECAM-B detection
  75. EP250901a: Global MASTER-Net observations report
  76. GRB 250830C: AstroSat CZTI detection of a long burst
  77. EP250901a: Einstein Probe detection of an X-ray transient
  78. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  79. EP250831a: EP-FXT follow-up observation
  80. EP250831a: Swift-XRT observations
  81. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  82. IceCube Alert 250831.75: Global MASTER-Net observations report
  83. EP250831a: Global MASTER-Net observations report
  84. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  85. EP250831a: EP-WXT detection of a fast X-ray transient
  86. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  87. GRB 250831A: Swift-XRT counterpart detection
  88. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  89. GRB 250831A: SVOM/VT upper limit with VHF data
  90. GRB 250831A: SVOM detection of a soft burst
  91. GRB 250830B: Swift-XRT observations
  92. EP250830a: Global MASTER-Net observations report
  93. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  94. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  95. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  96. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  97. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  98. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  99. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  100. GRB 250830B: Swift ToO 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