Skip to main content
New! BOOM Notices and Schema v7.0.0. 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"

20480 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  2. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  3. GRB 251202A: GOTO optical afterglow detection
  4. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  5. GRB 251202A: Swift-XRT afterglow detection
  6. Fermi GRB 251202A: Global MASTER-Net observations report
  7. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  8. Swift GRB 251201B: Global MASTER-Net observations report
  9. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  10. EP251130a: Mondy optical observations
  11. EP251130a: Optical detections with Kinder observations
  12. SVOM GRB251201.19: Global MASTER-Net observations report
  13. EP251130a: SAO RAS optical observations
  14. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  15. EP251130a: KAIT optical observations
  16. EP251130A: Optical observation from 1.3m DFOT
  17. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  18. EP251130a: JinShan optical observations
  19. Fermi GRB 251130B: Global MASTER-Net observations report
  20. IceCube Alert 251130.75: Global MASTER-Net observations report
  21. EP251130a: Swift-XRT counterpart detection
  22. EP251130a: Global MASTER-Net observations report
  23. EP251129a/GRB 251129A: EP-FXT follow-up observations
  24. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  25. GRB 251129A / EP251129a: SAO RAS optical observations
  26. GRB 251126A: SAO RAS optical observations
  27. GRB 251129A: Swift-XRT afterglow detection
  28. GRB 251129A: Swift ToO observations
  29. EP251129a: Global MASTER-Net observations report
  30. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  31. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  32. SVOM GRB251129A: Global MASTER-Net observations report
  33. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  34. Fermi GRB 251128A: Global MASTER-Net observations report
  35. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  36. GRB 251126A: further SAO RAS optical observations
  37. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  38. GRB 251126A NUTTelA-TAO Early Measurements
  39. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  40. GRB251126A: MAO/AZT-22 optical observations
  41. GRB251126A: Continued optical observation from 1.3m DFOT
  42. GRB 251126A: Swift/UVOT Detection
  43. GRB 251126A: Mondy and SAO RAS optical observations
  44. GRB 251126A: NOT optical observations
  45. GRB 251126A: 1.3m DFOT optical afterglow detection
  46. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  47. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  48. Fermi GRB 251127A: Global MASTER-Net observations report
  49. GRB 251126A: Kilonova-Catcher optical afterglow detection
  50. GRB 251126A: Asiago i-band detection
  51. GRB 251126A: Nanshan/HMT optical afterglow detection
  52. Swift GRB 251126A: Global MASTER-Net observations report
  53. GRB 251126A: GIT discovery of the likely optical afterglow
  54. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  55. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  56. EP251124b: NOT r- and z-band optical upper limits
  57. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  58. Fermi GRB 251125B: Global MASTER-Net observations report
  59. EP251124b: Global MASTER-Net observations report
  60. Fermi GRB 251125A: Global MASTER-Net observations report
  61. EP251124a: NOT r- and z-band optical upper limits
  62. EP251124a: Global MASTER-Net observations report
  63. EP251124a: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  65. EP251124a: Optical upper limit with Kinder observations
  66. EP251118A: 6 GHz VLA Detection
  67. Fermi GRB 251124a: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  69. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  70. GRB 251116C: Swift-XRT confirmation of fading
  71. GRB 251122A/EP251122a: FTW optical and NIR observations
  72. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  73. EP251118A: 3.6m DOT optical afterglow detection
  74. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  75. GRB 251122A / EP251122a: WFST optical observations
  76. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  77. GRB 251122A / EP251122a: LCO optical upper limits
  78. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  79. EP251122a: Global MASTER-Net observations report
  80. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  81. EP251118a: Continued Optical Detection with Kinder observations
  82. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  83. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  84. EP251118a: Xinglong-2.16m optical observation
  85. Fermi trigger No 785388351: Global MASTER-Net observations report
  86. EP251118A: 1.3m DFOT optical afterglow detection
  87. GRB 251118A: Swift/UVOT Detection
  88. EP251118a / GRB 251118C: SAO RAS optical observations
  89. GRB 251118A: Swift-XRT afterglow detection
  90. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  91. EP251118a: Optical detection with Kinder observations
  92. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  93. EP251118a / GRB 251118C: SVOM/VT optical observation
  94. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  95. GRB 251116C: NOT optical observations
  96. GRB 251117A: Swift-XRT observations
  97. EP251118A / GRB 251118C : MASTER optical counterpart observations
  98. EP251118a: FTW optical and NIR observations
  99. EP251118a: VLT near-infrared observation
  100. EP251118a: GOTO optical afterglow detection

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