Skip to main content
New! CHIME and DSA-110 FRB Notices, IceCube Notices and Schema v6.1.1. 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. Fermi GRB 250919A: Global MASTER-Net observations report
  2. GRB 250919A: Fermi GBM Final Real-time Localization
  3. GRB 250916A: KAIT optical observations
  4. GRB 250917B: VLT/HAWK-I near-infrared observations
  5. GRB 250916A: NuSTAR detection of the prompt emission
  6. GRB 250916A: further SAO RAS optical observations
  7. GRB 250912A: SVOM/ECLAIRs refined analysis
  8. GRB 250917B: Swift-BAT refined analysis
  9. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  10. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  11. GRB 250918A: Fermi GBM Final Real-time Localization
  12. GRB 250917B: Swift/UVOT Upper Limits
  13. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  14. GRB 250916A: Swift-XRT observations
  15. EP250916a: EP-FXT follow-up observation
  16. GRB 250916A: MAO/AZT-22 optical observations
  17. GRB 250916A: SAO RAS optical observations
  18. GRB 250916A : GIT optical observations
  19. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  20. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  21. GRB 250916A: Glowbug gamma-ray detection
  22. GRB250917B: WFST optical observations
  23. GRB 250916A: Swift ToO observations
  24. GRB 250917B: Fermi GBM Observation
  25. GRB 250917B: Swift-XRT observations
  26. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  27. Fermi GRB 250917B: Global MASTER-Net observations report
  28. GRB 250917B: Swift detection of a short burst
  29. GRB 250916A: GOTO optical counterpart candidate
  30. GRB 250917B: Fermi GBM Final Real-time Localization
  31. GRB 250917A: Fermi GBM Final Real-time Localization
  32. The EP-WXT trigger 01709241037 is likely a flaring star
  33. GRB 250916A: AstroSat CZTI detection of a bright long burst
  34. GRB 250910A: SVOM/ECLAIRs refined analysis
  35. EP250916a: Einstein Probe detection of an X-ray transient
  36. Fermi GRB 250916A: Global MASTER-Net observations report
  37. GRB 250916A: Fermi GBM Final Real-time Localization
  38. EP250827b: VLA Observations
  39. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  40. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  41. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  42. SVOM/sb25091517: SVOM detection of an X-ray transient
  43. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  44. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  45. GRB 250912A: Swift-XRT observations
  46. GRB250912A: VLT/HAWK-I follow-up observations
  47. GRB 250912A: VLT observations
  48. GRB 250912A: Fermi GBM Observation
  49. GRB 250911A: Insight-HXMT detection
  50. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  51. GRB 250912A:SVOM/VT optical upper limit
  52. GRB 250912A: LCO optical upper limit
  53. The EP-WXT trigger 01709240768 is likely a flaring star
  54. Fermi GRB 250912A: Global MASTER-Net observations report
  55. EP250911a: Global MASTER-Net observations report
  56. GRB 250912A: SVOM detection of a burst
  57. GRB 250912A: Fermi GBM Final Real-time Localization
  58. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  59. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  60. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  61. EP250911a: Upper limit from Fermi-GBM Observations
  62. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  63. GRB 250911A: GECAM-B detection
  64. GRB 250911A: Swift-BAT refined analysis
  65. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  66. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  67. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  68. GRB 250910B: SVOM/GRM observation
  69. EP250911a: SVOM/VT optical observation
  70. GRB 250911A: MASTER optical counterpart observations
  71. EP250911a: SAO RAS optical observations
  72. GRB 250911A: Swift-XRT refined Analysis
  73. GRB 250910C: Fermi GBM Final Localization Correction
  74. EP250911a: Swift-XRT observations
  75. EP250911a: Optical detection with Kinder observations
  76. GRB 250911A: Swift/UVOT Detection
  77. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  78. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  79. GRB 250909B: Insight-HXMT detection
  80. GRB 250909B: SVOM/GRM observation
  81. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  82. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  83. EP250911a: COLIBRÍ optical observations
  84. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  85. Fermi GRB 250910B: Global MASTER-Net observations report
  86. EP250911a: LCO optical counterpart discovery
  87. EP250910a: Global MASTER-Net observations report
  88. EP250911a: Einstein Probe detection of an X-ray transient
  89. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  90. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  91. GRB 250903A: SVOM/ECLAIRs refined analysis
  92. GRB 250911A: Enhanced Swift-XRT position
  93. GRB 250911A: Swift-XRT observations
  94. GRB 250911A: COLIBRÍ optical counterpart candidate
  95. GRB 250911A: Swift detection of a burst
  96. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  97. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  98. GRB 250910B: Fermi GBM Final Real-time Localization
  99. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  100. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient

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