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"

17024 results found.

  1. EP251130a: MAO/AZT-22 optical observations
  2. EP251202a/GRB 251202A: KAIT optical observations
  3. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  4. IPN triangulation of GRB 251129B (short/hard)
  5. GRB251129A/EP251129a: Swift UVOT detection
  6. GRB 251202A: Swift/UVOT Detection
  7. GRB 251201B: Kilonova-Catcher optical afterglow detection
  8. GRB 251201B: Swift/UVOT Detection
  9. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  10. GRB 251126A: SAO RAS optical marginal detection
  11. GRB 251202A: Swift-XRT afterglow detection
  12. EP251129a/GRB 251129A: NOWT Detection
  13. GRB 251126A: SVOM/VT optical observation
  14. EP251130a: SVOM/VT optical observation
  15. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  16. GRB 251201A: SVOM/GRM observation of a burst
  17. GRB 251201B: SVOM/VT optical fading
  18. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  19. GRB 251201B: Enhanced Swift-XRT position
  20. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  21. GRB 251201B: Swift detection of a burst with an optical counterpart
  22. EP251130a: Mondy optical observations
  23. EP251130a: Optical detections with Kinder observations
  24. EP251130a: SAO RAS optical observations
  25. EP251130A: Optical observation from 1.3m DFOT
  26. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  27. EP251130a: JinShan optical observations
  28. GRB 251127A: SVOM/GRM observation
  29. EP251130a: COLIBRÍ optical counterpart candidate
  30. EP251130a: Einstein Probe detection of an X-ray transient
  31. EP251129a/GRB 251129A: EP-FXT follow-up observations
  32. GRB 251129A / EP251129a: SAO RAS optical observations
  33. GRB 251126A: SAO RAS optical observations
  34. GRB 251128A: SVOM/GRM observation of a long burst
  35. SVOM GRB 251129A : MASTER optical counterpart detection
  36. GRB 251129A: Swift-XRT afterglow detection
  37. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  38. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  39. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  40. GRB 251129A: SVOM detection of a burst
  41. SVOM GRB251129A: Global MASTER-Net observations report
  42. GRB 251129A: SVOM detection of a burst
  43. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  44. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  45. GRB 251126A: further SAO RAS optical observations
  46. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  47. GRB251126A: MAO/AZT-22 optical observations
  48. GRB251126A: Continued optical observation from 1.3m DFOT
  49. GRB 251126A: Swift/UVOT Detection
  50. GRB 251126A: Mondy and SAO RAS optical observations
  51. GRB 251126A: Swift-XRT refined Analysis
  52. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  53. GRB 251126A: 1.3m DFOT optical afterglow detection
  54. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  55. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  56. GRB 251126A: Enhanced Swift-XRT position
  57. GRB 251126A: Kilonova-Catcher optical afterglow detection
  58. GRB 251126A: Nanshan/HMT optical afterglow detection
  59. GRB 251126A: GIT discovery of the likely optical afterglow
  60. GRB 251126A: Swift detection of a burst
  61. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  62. EP251124b follow-up observation by EP-FXT
  63. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  64. EP251124b: NOT r- and z-band optical upper limits
  65. EP251124b: EP-WXT detection of a fast X-ray transient
  66. EP251124a: Xinglong GWAC-F60A optical observation
  67. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  68. EP251124a: NOT r- and z-band optical upper limits
  69. EP251124a: Swift-XRT observations
  70. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  71. EP251124a: Optical upper limit with Kinder observations
  72. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  73. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  74. EP251124a: GROWTH-India Telescope optical upper limits
  75. EP251124a: Einstein Probe detection of an X-ray transient
  76. GRB 251116C: Swift-XRT confirmation of fading
  77. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  78. The EP-WXT trigger 01709248783 is likely a flaring star
  79. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  80. EP251118A: 3.6m DOT optical afterglow detection
  81. GRB 251122A / EP251122a: EP-FXT counterpart detection
  82. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  83. GRB 251122A / EP251122a: WFST optical observations
  84. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  85. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  86. GRB 251122A / EP251122a: LCO optical upper limits
  87. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  88. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  89. GRB 251122A / EP251122a: SVOM detection of a long burst
  90. EP251122a: Einstein Probe detection of an X-ray transient
  91. EP251118a: Continued Optical Detection with Kinder observations
  92. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  93. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  94. EP251118a: Xinglong-2.16m optical observation
  95. The EP-WXT trigger 01709248635 is likely a flaring star
  96. EP251118A: 1.3m DFOT optical afterglow detection
  97. GRB 251118A: Swift/UVOT Detection
  98. EP251118a / GRB 251118C: SAO RAS optical observations
  99. GRB 251118A: Swift-XRT afterglow detection
  100. EP251118a: Optical detection with Kinder 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