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 S250221gb: Retraction of GW compact binary merger candidate
  2. GRB 250221A: AKO Optical Upper Limit
  3. GRB 250221A: Swift/UVOT Detection
  4. EP250220a: Liverpool Telescope upper limits
  5. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  6. GRB 250221A: REM optical/NIR afterglow detection
  7. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  8. GRB 250221A: Enhanced Swift-XRT position
  9. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  10. EP250220a: 1.6m Mephisto observations
  11. EP250220a: Liverpool Telescope optical upper limits
  12. EP250220a: Optical upper limit with Kinder observations
  13. SVOM trigger sb25022102 is not an astrophysical event
  14. SVOM/sb25022102: SVOM detection of an X-ray transient
  15. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  16. GRB 250221A: Swift detection of a burst with an optical counterpart
  17. Swift GRB250221.15: Global MASTER-Net OT detection
  18. Swift GRB250221.15: Global MASTER-Net observations report
  19. EP250220a: Xinglong optical upper limit
  20. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  21. GRB 250220B: Fermi GBM Final Real-time Localization
  22. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  23. GRB 250220A: Fermi GBM Final Real-time Localization
  24. EP250220a: Global MASTER-Net observations report
  25. EP250220a: EP-WXT detection of a fast X-ray transient
  26. Konus-Wind detection of GRB 250217C (short)
  27. GRB 250219A: Swift/UVOT Upper Limits
  28. GRB 250219A: OHP/T193 optical upper limit
  29. GRB 250219A: NOT optical observations
  30. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  31. GRB 250219A: 1.6m Mephisto optical upper limits
  32. GRB 250219A: SVOM/VT optical counterpart
  33. GRB 250219A: Swift-XRT observations
  34. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  35. GRB 250219A: Swift ToO observations
  36. GRB 250219A: SVOM detection of a burst
  37. Konus-Wind detection of GRB 250215A / EP250215a
  38. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  39. GRB 250217C: Swift-XRT observations
  40. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  41. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  42. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  43. GRB 250217C: SVOM/GRM observation
  44. GRB 250217C: Tiled Swift observations
  45. GRB 250217C: Fermi GBM Observation
  46. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  47. IPN triangulation of GRB 250217C (short)
  48. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  49. SVOM/sb25021804: SVOM detection of a long X-ray transient
  50. GRB 250213A: Swift-XRT observations
  51. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  52. GRB 250216A: AstroSat CZTI detection
  53. GRB 250217C: AstroSat CZTI detection of a short burst
  54. Fermi GRB 250217C: Global MASTER-Net observations report
  55. GRB 250217C: Fermi GBM Final Real-time Localization
  56. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  57. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  58. Fermi GRB 250217A: Global MASTER-Net observations report
  59. GRANDMA/OPD observations of GRB250215A
  60. GRB 250217B: Fermi GBM Final Real-time Localization
  61. The EP-WXT trigger 01709131775 is likely a flaring star
  62. GRB 250217A: Fermi GBM Final Real-time Localization
  63. Fermi GRB 250216A: Global MASTER-Net observations report
  64. GRB 250215A / EP250215a: LCO detection of the afterglow
  65. GRB 250216A: Fermi GBM Final Real-time Localization
  66. EP250212a: FTW optical and NIR upper limits
  67. GRB 250215A: Swift/UVOT Upper Limits
  68. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  69. EP250215a / GRB 250215A : GTC redshift z = 4.61
  70. GRB 250215A: Fermi GBM Observation
  71. EP250215a / GRB 250215A : NOT optical observations
  72. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  73. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  74. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  75. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  76. GRB 250215A: Swift-XRT refined Analysis
  77. GRB 250215A: SVOM/GRM observation
  78. EP250215a / GRB 250215A: AstroSat CZTI detection
  79. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  80. EP250215a: Global MASTER-Net observations report
  81. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  82. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  83. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  84. Fermi GRB 250215A: Global MASTER-Net observations report
  85. GRB 250215A: Fermi GBM Final Real-time Localization
  86. Fermi trigger No 761206993: Global MASTER-Net observations report
  87. GRB 250213A：SVOM/VT optical candidate
  88. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  89. EP250207b: Xinglong optical upper limit
  90. Fermi GRB 250214A: Global MASTER-Net observations report
  91. GRB 250213A: Swift ToO observations
  92. GRB 250214A: Fermi GBM Final Real-time Localization
  93. EP250212a: Xinglong optical upper limit
  94. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  95. GRB 250213A: SVOM detection of a burst
  96. EP250212a: Global MASTER-Net observations report
  97. GRB 250205A: VIRT Optical Upper Limit
  98. GRB 250205A: Leavitt Observatory optical upper limit
  99. GRB 250210A: GRBAlpha detection
  100. EP250207B: Chandra localization of the X-ray counterpart

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