Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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 250109A / EP250109a: Mephisto optical upper limits
  2. EP250108a: Mephisto detection
  3. EP250111a: Mondy optical observation
  4. EP250108a / AT 2025kg: LCO optical observations
  5. EP250111a: Global MASTER-Net observations report
  6. EP250111a: Swift/XRT detection and fading
  7. EP250108a / AT 2025kg: Swift UVOT detections
  8. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  9. EP250108a: optical follow-up observations with the Liverpool Telescope
  10. EP250111a: NOT likely optical counterpart
  11. EP250111a: a new X-ray transient detected by Einstein Probe
  12. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  13. GRB 250101B: Fermi GBM Observation
  14. EP250108a: further NOT optical observations
  15. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  16. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  17. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  18. GRB 250108A: Swift/XRT afterglow fading
  19. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  20. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  21. Konus-Wind detection of GRB 250107C
  22. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  23. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  24. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  25. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  26. GRB 250101A: CMO RC-500 optical observations
  27. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  28. EP250108a: EP-FXT follow-up observation
  29. GRB 250109A: Fermi GBM Observation
  30. The EP-WXT trigger 01709130111 is likely a flaring star
  31. EP250108a: NOT optical observations
  32. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  33. GRB 250109a: GMG Optical Upper Limit
  34. EP250109a: Swift/UVOT non-detection
  35. Konus-Wind detection of GRB 250107D (short/hard)
  36. IPN triangulation of GRB 250107D (short/hard)
  37. IPN triangulation of GRB 250107C
  38. EP250108a: Liverpool Telescope likely optical counterpart
  39. GRB 250108B: Gemini-North likely redshift z = 2.197
  40. GRB 250108B: Swift-BAT refined analysis
  41. GRB 250108B: 1.3m DFOT upper limit
  42. GRB 250108B: REM optical/NIR upper limits
  43. GRB 250109A /EP250109a: Fermi GBM Final Localization
  44. EP250109a: SVOM/VT optical candidate
  45. EP250109a: Global MASTER-Net observations report
  46. GRB 250107C: SVOM/GRM observation
  47. GRB 250101A: Terskol K-800 optical observations
  48. EP250109a: GOTO optical upper limits
  49. EP250109a: Swift/XRT non-detection
  50. GRB 250108A: Swift/UVOT Upper Limits
  51. EP250108a: Global MASTER-Net observations report
  52. EP250109a: EP-WXT detection of an X-ray transient
  53. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  54. GRB 250108A: NOT optical upper limit
  55. EP250108a: EP-WXT detection of an X-ray transient
  56. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  57. GRB 250108B: Swift-XRT refined Analysis
  58. Swift GRB 250108B: Global MASTER-Net observations report
  59. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  60. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  61. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  62. GRB 250103A: 1.6m Mephisto optical observations
  63. GRB 250108A: Swift-XRT afterglow detection
  64. GRB 250108A:SVOM/VT optical candidate
  65. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  66. GRB 250108B: Swift/UVOT Upper Limits
  67. GRB 250103A: Swift-XRT afterglow detection
  68. GRB 250108B: Enhanced Swift-XRT position
  69. GRB 250108B: Swift detection of a burst
  70. GRB 250108A: Swift ToO observations
  71. GRB 250108A: SVOM detection of a soft long burst
  72. GRB 250107A: Fermi GBM Observation
  73. GRB 241228B: Fermi-LAT detection
  74. Fermi GRB 250107B: Global MASTER-Net observations report
  75. GRB 250107A: Swift ToO observations
  76. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  77. GRB 250107B: Fermi GBM Final Real-time Localization
  78. GRB 250106A: SVOM/VT 2nd optical deep observation
  79. GRB 250101A: J band upper limit by SYSU 80cm telescope
  80. GRB 250107A: Fermi GBM Final Real-time Localization
  81. EPWXT01709129925: Xinglong optical observations
  82. GRB 250106A: NOT optical observations
  83. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  84. GRB 250103B: REM optical/NIR upper limits
  85. GRB 250101A: REM optical/NIR counterpart detection
  86. GRB 250106A: Swift-XRT observations
  87. GRB 250106A: SVOM/VT optical candidate
  88. GRB 250106A: Swift ToO observations
  89. The EP-WXT trigger 01709129925 is likely a flaring star
  90. GRB 250106A: SVOM detection of a long burst
  91. Fermi trigger No 757753930: Global MASTER-Net observations report
  92. GRB 241229A: SVOM/VT optical upperlimit
  93. GRB 250103B: Swift-XRT refined Analysis
  94. GRB 250103B: LCO/1m optical afterglow candidate detection
  95. GRB 250103A: Bassano Bresciano Observatory upper limit
  96. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  97. GRB 250103A: Swift-XRT observations
  98. GRB 250101A: 1.3m DFOT optical afterglow detection
  99. GRB 241229A: 1.3m DFOT upper limit
  100. GRB 241228B: 1.3m DFOT Optical observations

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