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 250904A: TRT optical counterpart detection
  2. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  3. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  4. GRB 250904A: Prompt enhanced Swift-XRT position
  5. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  6. GRB 250904A: Swift detection of a burst
  7. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  8. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  9. GRB 250902A: VZLUSAT-2 detection
  10. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  11. GRB 250903A: Swift-XRT observations
  12. EP250903a: Swift-XRT observations
  13. EP#01709201209: Swift-XRT observations
  14. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  15. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  16. GRB 250830C: VZLUSAT-2 detection
  17. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  18. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  19. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  20. The EP-WXT trigger 01709201209 is likely a flaring star
  21. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  22. GRB 250903A: EP-FXT counterpart detection
  23. GRB 250902A: GECAM-B detection
  24. GRB 250903A: LCO optical observation
  25. GRB 250903A: LCO optical afterglow detection
  26. GRB 250903A: SVOM/VT optical confirmation with VHF data
  27. EP250903a: SVOM/VT optical confirmation
  28. EP250901a: Mondy, Assy and SAO RAS optical limits
  29. Subject GRB 250903A: SVOM/MXT afterglow detection
  30. EP250903a: LCO candidate counterpart discovery
  31. GRB 250903A: TRT optical counterpart detection
  32. GRB 250902B: AstroSat CZTI detection
  33. GRB 250903A: SVOM detection of a burst
  34. EP250903a: Global MASTER-Net observations report
  35. EP250903a: TRT optical observations
  36. EP250903a: Einstein Probe detection of an X-ray transient
  37. EP 250827B: Detection of supernova counterpart by LCO.
  38. EP/WXT01709201159: GOTO optical follow-up
  39. EP250827b / AT 2025wkm: TRT optical observations
  40. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  41. EP250827b: continued Liverpool Telescope observations
  42. GRB 250902B: SVOM/GRM observation
  43. EP250827b: SVOM/VT observation of AT 2025wkm
  44. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  45. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  46. Fermi GRB 250902B: Global MASTER-Net observations report
  47. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  48. GRB 250902A: Fermi GBM Detection
  49. GRB 250901A: Swift/UVOT Upper Limit
  50. GRB 250902B: Fermi GBM Final Real-time Localization
  51. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 250830B: Swift-XRT afterglow detection
  53. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  54. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  55. EP250827b: Liverpool Telescope observations
  56. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  57. GRB 250902A: SVOM/GRM observation
  58. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  59. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  60. GRB 250901A: EP-FXT follow-up observation
  61. GRB 250901A: NOT optical observations
  62. GRB 250902A: Fermi GBM Final Real-time Localization
  63. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  64. GRB 250901A: SVOM/VT optical afterglow with VHF data
  65. GRB 250901A: Swift-XRT afterglow detection
  66. EP250901a: Swift-XRT observations
  67. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  68. GRB 250901A: LCO optical upper limit
  69. EP250827b: Swift observations of AT 2025wkm
  70. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  71. EP250827b: Gemini Spectroscopy of AT 2025wkm
  72. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  73. EP250831a: NOT optical observations and tentative afterglow candidate
  74. EP250827b: FTW Observations of AT 2025wkm
  75. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  76. GRB 250901A: SVOM detection of a burst
  77. GRB 250831B: SVOM/GRM observation
  78. GRB 250830C: Insight-HXMT detection
  79. EP250901a: Mephisto optical upper limits
  80. GRB 250830C: GECAM-B detection
  81. EP250901a: Global MASTER-Net observations report
  82. GRB 250830C: AstroSat CZTI detection of a long burst
  83. EP250901a: Einstein Probe detection of an X-ray transient
  84. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  85. EP250831a: EP-FXT follow-up observation
  86. EP250831a: Swift-XRT observations
  87. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  88. IceCube Alert 250831.75: Global MASTER-Net observations report
  89. EP250831a: Global MASTER-Net observations report
  90. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  91. EP250831a: EP-WXT detection of a fast X-ray transient
  92. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  93. GRB 250831A: Swift-XRT counterpart detection
  94. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. GRB 250831A: SVOM/VT upper limit with VHF data
  96. GRB 250831A: SVOM detection of a soft burst
  97. GRB 250830B: Swift-XRT observations
  98. EP250830a: Global MASTER-Net observations report
  99. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  100. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC 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