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. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  2. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  3. EP250702a: WFST optical observations
  4. EP250704a: COLIBRÍ optical counterpart candidate
  5. EP250704a: Einstein Probe detection of an X-ray transient
  6. GRB 250704B: SVOM/GRM observation of a short burst
  7. GRB 250702F: optical photometry from Konkoly
  8. GRB 250704A: REM detection of the optical afterglow
  9. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  10. GRB 250702F: SVOM/VT optical observation
  11. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  12. GRB 250704A: SVOM detection of a burst
  13. GRB 250702F: Swift/UVOT Detection
  14. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  15. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  16. Fermi GRB 250703A: Global MASTER-Net observations report
  17. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  18. GRB 250702F: Swift-XRT refined Analysis
  19. GRB 250702F: Fermi GBM Observation
  20. GRB 250702F: Leavitt Observatory optical observations
  21. GRB 250702F: AKO Optical Afterglow Detection
  22. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  23. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  24. GRB 250702A: GECAM-B detection
  25. GRB 250702F: Skynet Optical Observations
  26. GRB 250424A: VIRT Optical Upper Limit
  27. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  28. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  29. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  30. GRB 250702F: TRT Optical Observation
  31. GRB 250703A: DDOTI Optical Upper Limit
  32. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  33. GRB 250702F: REM optical afterglow detection
  34. EP250702a: Global MASTER-Net observations report
  35. GRB 250702F: DDOTI Optical Observation
  36. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  37. GRB 250703A: Fermi GBM Final Real-time Localization
  38. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  39. GRB 250702F: COLIBRÍ Observations of the Afterglow
  40. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  41. Fermi GRB 250702E: Global MASTER-Net observations report
  42. Fermi GRB 250702B: Global MASTER-Net observations report
  43. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  44. GRB 250702F: Enhanced Swift-XRT position
  45. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  46. GRB 250702F: NOT observations of the optical afterglow
  47. GRB 250702F: MASTER optical afterglow observation
  48. Fermi GRB 250702F: Global MASTER-Net observations report
  49. Fermi GRB 250702C: Global MASTER-Net observations report
  50. GRB 250702F: GOTO optical counterpart detection
  51. GRB 250702F: Ondrejov D50 optical afterglow detection
  52. GRB 250702F: Swift detection of a burst with an optical counterpart
  53. Swift GRB 250702F: Global MASTER-Net observations report
  54. GRB 250702F: Fermi GBM Final Real-time Localization
  55. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  56. GRB 250702E: Fermi GBM Final Real-time Localization
  57. Konus-Wind detection of GRB 250627A
  58. IPN triangulation of GRB 250627A (short)
  59. GRB 250702A: Fermi GBM Detection
  60. GRB 250702D: Fermi GBM Final Localization Correction
  61. GRB 250702C: Fermi GBM Final Real-time Localization
  62. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  63. GRB 250702B: Fermi GBM Final Real-time Localization
  64. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  65. GRB 250702A: Fermi GBM Final Real-time Localization
  66. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  67. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  68. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  69. GRB 250628B: Swift-XRT observations
  70. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  71. GRB 250628B: SVOM/VT optical upper limit
  72. GRB 250628B: EP-FXT counterpart detection
  73. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  74. GRB 250627A: Insight-HXMT detection
  75. GRB 250627A: SVOM/GRM detection of a short burst
  76. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  77. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  79. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  81. GRB 250628A: REM optical/NIR upper limits
  82. GRB 250628C: Fermi GBM Final Real-time Localization
  83. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  84. GRB 250628B: SVOM detection of a long burst
  85. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  86. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  87. GRB 250628A: VLT/X-shooter upper limits
  88. GRB 250628A: Swift/UVOT Upper Limits
  89. GRB 250628A: Swift-XRT refined Analysis
  90. Fermi GRB 250626A: Global MASTER-Net observations report
  91. Swift GRB 250628A: Global MASTER-Net observations report
  92. GRB 250628A: Enhanced Swift-XRT position
  93. GRB 250628A: Swift detection of a burst
  94. GRB 250625A: Swift-BAT refined analysis
  95. GRB 250625A: Leavitt Observatory afterglow detection
  96. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  97. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  98. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  99. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  100. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy

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