Skip to main content
Due to the lapse in federal government funding, NASA is not updating this website. See the Operations FAQ for GCN impacts.
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. GRB 250912A: Swift-XRT observations
  3. GRB250912A: VLT/HAWK-I follow-up observations
  4. GRB 250912A: VLT observations
  5. GRB 250912A: Fermi GBM Observation
  6. GRB 250911A: Insight-HXMT detection
  7. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  8. GRB 250912A:SVOM/VT optical upper limit
  9. GRB 250912A: LCO optical upper limit
  10. The EP-WXT trigger 01709240768 is likely a flaring star
  11. Fermi GRB 250912A: Global MASTER-Net observations report
  12. EP250911a: Global MASTER-Net observations report
  13. GRB 250912A: SVOM detection of a burst
  14. GRB 250912A: Fermi GBM Final Real-time Localization
  15. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  16. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  17. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  18. EP250911a: Upper limit from Fermi-GBM Observations
  19. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  20. GRB 250911A: GECAM-B detection
  21. GRB 250911A: Swift-BAT refined analysis
  22. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  23. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  24. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  25. GRB 250910B: SVOM/GRM observation
  26. EP250911a: SVOM/VT optical observation
  27. GRB 250911A: MASTER optical counterpart observations
  28. EP250911a: SAO RAS optical observations
  29. GRB 250911A: Swift-XRT refined Analysis
  30. GRB 250910C: Fermi GBM Final Localization Correction
  31. EP250911a: Swift-XRT observations
  32. EP250911a: Optical detection with Kinder observations
  33. GRB 250911A: Swift/UVOT Detection
  34. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  35. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  36. GRB 250909B: Insight-HXMT detection
  37. GRB 250909B: SVOM/GRM observation
  38. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  39. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  40. EP250911a: COLIBRÍ optical observations
  41. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  42. Fermi GRB 250910B: Global MASTER-Net observations report
  43. EP250911a: LCO optical counterpart discovery
  44. EP250910a: Global MASTER-Net observations report
  45. EP250911a: Einstein Probe detection of an X-ray transient
  46. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  47. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  48. GRB 250903A: SVOM/ECLAIRs refined analysis
  49. GRB 250911A: Enhanced Swift-XRT position
  50. GRB 250911A: Swift-XRT observations
  51. GRB 250911A: COLIBRÍ optical counterpart candidate
  52. GRB 250911A: Swift detection of a burst
  53. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  54. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  55. GRB 250910B: Fermi GBM Final Real-time Localization
  56. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  57. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  58. GRB 250909B: AstroSat CZTI detection of a long burst
  59. GRB 250910A: SVOM/VT optical upper limit
  60. EP250908C: GROND observation of the fading optical counterpart
  61. GRB 250910A: LCO optical upper limit
  62. GRB 250909A: AstroSat CZTI detection
  63. GRB 250910A: SVOM/MXT possible afterglow detection
  64. GRB 250910A: SVOM detection of a faint burst
  65. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  66. GRB 250702B: Late time Chandra observations
  67. EP250908b/EP#01709240653: Swift/UVOT Detection
  68. EP#01709240653: Swift-XRT observations
  69. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  70. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  71. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  72. EP250908c: SVOM/VT optical observation
  73. EP250908c: VLT/FORS2 optical counterpart identification
  74. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  75. EP250908b: SVOM/VT optical candidate
  76. The EP-WXT trigger EP250908a/01709240652 is not a real source
  77. EP250908c: Global MASTER-Net observations report
  78. Fermi GRB 250909A: Global MASTER-Net observations report
  79. EP250908c: Einstein Probe detection of an X-ray transient
  80. GRB 250909A: Fermi GBM Final Real-time Localization
  81. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  82. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  83. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  84. GRB 250907A: GECAM-B detection
  85. GRB 250905A: Swift-BAT refined analysis
  86. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  87. GRB 250903A: Swift-XRT afterglow detection
  88. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  89. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  90. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  91. EP250905a: Liverpool Telescope i-band upper limits
  92. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  93. EP250905b: EP-FXT follow-up observation
  94. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  95. EP250905a: Liverpool Telescope observations
  96. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  97. EP250905b: Global MASTER-Net observations report
  98. EP250905b: EP-WXT detection of a fast X-ray transient
  99. EP250905a: FTW one optical and multiple NIR counterpart candidates
  100. GRB 250905A: Swift-XRT refined Analysis

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