Skip to main content
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. EP250223a: 1.6m Mephisto and 50cm array observations
  2. GRB 250221A: TNOT detection of the optical counterpart
  3. EP250223a: SVOM/VT optical observation
  4. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  5. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  6. The EP-WXT trigger 01709131882 is likely a flaring star
  7. EP250223a: OASDG optical observations
  8. EP250223a: LCO detection of the afterglow
  9. EP250223a: early optical detection by BOOTES-4
  10. EP250223a: NOT redshift z = 2.756
  11. EP250223a: Swift/XRT localization
  12. EP250223a: NOT optical afterglow candidate
  13. GRB 250223B: Fermi GBM Final Localization
  14. EP250223a: Global MASTER-Net observations report
  15. GRB 250221A: VLA radio detection
  16. Fermi GRB 250223A: Global MASTER-Net observations report
  17. Fermi trigger No 762020305: Global MASTER-Net observations report
  18. GRB 250223A: Fermi GBM Final Real-time Localization
  19. EP250223a: Einstein Probe detection of an X-ray transient
  20. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  21. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  22. GRB 250221A: continued Mondy optical observations, brightening afterglow
  23. GRB 250221A: Optical counterpart detection by LCO.
  24. GRB 250221A: Mondy optical observations
  25. Konus-Wind detection of GRB 250221A
  26. GRB 250221A: Assy optical observations
  27. EP250220a: FTW optical and NIR observations and upper limits
  28. EP250220a: EP-FXT follow-up observations
  29. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  30. GRB 250221A: VLT/X-shooter redshift z = 0.768
  31. GRB 250221A: GRANDMA/TAROT Detection
  32. Fermi trigger No 761805304: Global MASTER-Net observations report
  33. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  34. GRB 250221A: Swift-XRT refined Analysis
  35. GRB 250221A: NOT optical observations
  36. GRB 250221A: 1.6m Mephisto optical detection
  37. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  38. GRB 250221A: AKO Optical Upper Limit
  39. GRB 250221A: Swift/UVOT Detection
  40. EP250220a: Liverpool Telescope upper limits
  41. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  42. GRB 250221A: REM optical/NIR afterglow detection
  43. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  44. GRB 250221A: Enhanced Swift-XRT position
  45. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  46. EP250220a: 1.6m Mephisto observations
  47. EP250220a: Liverpool Telescope optical upper limits
  48. EP250220a: Optical upper limit with Kinder observations
  49. SVOM trigger sb25022102 is not an astrophysical event
  50. SVOM/sb25022102: SVOM detection of an X-ray transient
  51. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  52. GRB 250221A: Swift detection of a burst with an optical counterpart
  53. Swift GRB250221.15: Global MASTER-Net OT detection
  54. Swift GRB250221.15: Global MASTER-Net observations report
  55. EP250220a: Xinglong optical upper limit
  56. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  57. GRB 250220B: Fermi GBM Final Real-time Localization
  58. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  59. GRB 250220A: Fermi GBM Final Real-time Localization
  60. EP250220a: Global MASTER-Net observations report
  61. EP250220a: EP-WXT detection of a fast X-ray transient
  62. Konus-Wind detection of GRB 250217C (short)
  63. GRB 250219A: Swift/UVOT Upper Limits
  64. GRB 250219A: OHP/T193 optical upper limit
  65. GRB 250219A: NOT optical observations
  66. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  67. GRB 250219A: 1.6m Mephisto optical upper limits
  68. GRB 250219A: SVOM/VT optical counterpart
  69. GRB 250219A: Swift-XRT observations
  70. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  71. GRB 250219A: Swift ToO observations
  72. GRB 250219A: SVOM detection of a burst
  73. Konus-Wind detection of GRB 250215A / EP250215a
  74. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  75. GRB 250217C: Swift-XRT observations
  76. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  77. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  78. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  79. GRB 250217C: SVOM/GRM observation
  80. GRB 250217C: Tiled Swift observations
  81. GRB 250217C: Fermi GBM Observation
  82. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  83. IPN triangulation of GRB 250217C (short)
  84. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  85. SVOM/sb25021804: SVOM detection of a long X-ray transient
  86. GRB 250213A: Swift-XRT observations
  87. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  88. GRB 250216A: AstroSat CZTI detection
  89. GRB 250217C: AstroSat CZTI detection of a short burst
  90. Fermi GRB 250217C: Global MASTER-Net observations report
  91. GRB 250217C: Fermi GBM Final Real-time Localization
  92. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  93. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  94. Fermi GRB 250217A: Global MASTER-Net observations report
  95. GRANDMA/OPD observations of GRB250215A
  96. GRB 250217B: Fermi GBM Final Real-time Localization
  97. The EP-WXT trigger 01709131775 is likely a flaring star
  98. GRB 250217A: Fermi GBM Final Real-time Localization
  99. Fermi GRB 250216A: Global MASTER-Net observations report
  100. GRB 250215A / EP250215a: LCO detection of the afterglow

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