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. GRB 250221A: Enhanced Swift-XRT position
  2. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  3. EP250220a: 1.6m Mephisto observations
  4. EP250220a: Liverpool Telescope optical upper limits
  5. EP250220a: Optical upper limit with Kinder observations
  6. SVOM trigger sb25022102 is not an astrophysical event
  7. SVOM/sb25022102: SVOM detection of an X-ray transient
  8. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  9. GRB 250221A: Swift detection of a burst with an optical counterpart
  10. Swift GRB250221.15: Global MASTER-Net OT detection
  11. Swift GRB250221.15: Global MASTER-Net observations report
  12. EP250220a: Xinglong optical upper limit
  13. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  14. GRB 250220B: Fermi GBM Final Real-time Localization
  15. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  16. GRB 250220A: Fermi GBM Final Real-time Localization
  17. EP250220a: Global MASTER-Net observations report
  18. EP250220a: EP-WXT detection of a fast X-ray transient
  19. Konus-Wind detection of GRB 250217C (short)
  20. GRB 250219A: Swift/UVOT Upper Limits
  21. GRB 250219A: OHP/T193 optical upper limit
  22. GRB 250219A: NOT optical observations
  23. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  24. GRB 250219A: 1.6m Mephisto optical upper limits
  25. GRB 250219A: SVOM/VT optical counterpart
  26. GRB 250219A: Swift-XRT observations
  27. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  28. GRB 250219A: Swift ToO observations
  29. GRB 250219A: SVOM detection of a burst
  30. Konus-Wind detection of GRB 250215A / EP250215a
  31. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  32. GRB 250217C: Swift-XRT observations
  33. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  34. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  35. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  36. GRB 250217C: SVOM/GRM observation
  37. GRB 250217C: Tiled Swift observations
  38. GRB 250217C: Fermi GBM Observation
  39. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  40. IPN triangulation of GRB 250217C (short)
  41. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  42. SVOM/sb25021804: SVOM detection of a long X-ray transient
  43. GRB 250213A: Swift-XRT observations
  44. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  45. GRB 250216A: AstroSat CZTI detection
  46. GRB 250217C: AstroSat CZTI detection of a short burst
  47. Fermi GRB 250217C: Global MASTER-Net observations report
  48. GRB 250217C: Fermi GBM Final Real-time Localization
  49. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  50. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  51. Fermi GRB 250217A: Global MASTER-Net observations report
  52. GRANDMA/OPD observations of GRB250215A
  53. GRB 250217B: Fermi GBM Final Real-time Localization
  54. The EP-WXT trigger 01709131775 is likely a flaring star
  55. GRB 250217A: Fermi GBM Final Real-time Localization
  56. Fermi GRB 250216A: Global MASTER-Net observations report
  57. GRB 250215A / EP250215a: LCO detection of the afterglow
  58. GRB 250216A: Fermi GBM Final Real-time Localization
  59. EP250212a: FTW optical and NIR upper limits
  60. GRB 250215A: Swift/UVOT Upper Limits
  61. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  62. EP250215a / GRB 250215A : GTC redshift z = 4.61
  63. GRB 250215A: Fermi GBM Observation
  64. EP250215a / GRB 250215A : NOT optical observations
  65. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  66. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  67. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  68. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  69. GRB 250215A: Swift-XRT refined Analysis
  70. GRB 250215A: SVOM/GRM observation
  71. EP250215a / GRB 250215A: AstroSat CZTI detection
  72. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  73. EP250215a: Global MASTER-Net observations report
  74. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  75. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  76. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  77. Fermi GRB 250215A: Global MASTER-Net observations report
  78. GRB 250215A: Fermi GBM Final Real-time Localization
  79. Fermi trigger No 761206993: Global MASTER-Net observations report
  80. GRB 250213A：SVOM/VT optical candidate
  81. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  82. EP250207b: Xinglong optical upper limit
  83. Fermi GRB 250214A: Global MASTER-Net observations report
  84. GRB 250213A: Swift ToO observations
  85. GRB 250214A: Fermi GBM Final Real-time Localization
  86. EP250212a: Xinglong optical upper limit
  87. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  88. GRB 250213A: SVOM detection of a burst
  89. EP250212a: Global MASTER-Net observations report
  90. GRB 250205A: VIRT Optical Upper Limit
  91. GRB 250205A: Leavitt Observatory optical upper limit
  92. GRB 250210A: GRBAlpha detection
  93. EP250207B: Chandra localization of the X-ray counterpart
  94. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  95. EP250207b: VLA radio upper limits
  96. EP250212a: Liverpool Telescope optical upper limits
  97. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  98. GRB250101A: Radio upper limits from GMRT observations
  99. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  100. EP250207B: GTC z-band Observations

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