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"

21575 results found.

  1. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  2. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  3. Fermi trigger No 797912738: Global MASTER-Net observations report
  4. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  5. EP260321a: CMO SAI J,K observations
  6. Fermi GRB 260413A: Global MASTER-Net observations report
  7. EP260321a: SVOM/VT optical observations and color changes around peak
  8. Fermi GRB 260412A: Global MASTER-Net observations report
  9. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  10. GRB 260411B: COLIBRÍ optical observations
  11. GRB 260411B: Ondrejov D50 optical afterglow detection
  12. GRB260411B: 3.6m DOT optical observation
  13. GRB 260411B: GOTO optical counterpart candidate
  14. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  15. EP-WXT01709259790: Optical Upper limits with kinder observations
  16. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  17. EP260321a: Chandra X-ray Non-detection
  18. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  19. EP260409a: SVOM/VT optical upper limits
  20. EP260409a: Global MASTER-Net observations report
  21. EP260321a: VLA radio detection
  22. GRB 260402A: SVOM/ECLAIRs refined analysis
  23. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  24. GRB 260310A / AT2026fgk: X-ray rebrightening
  25. EP260402a / GRB 260402A: Mephisto optical upper limits
  26. EP260403a: Mephisto optical upper limits
  27. EP260321a: Upper limits from VLA radio observations
  28. EP260321a: uGMRT observations
  29. EP260405a: SVOM/VT optical upper limits
  30. EP260405a: Global MASTER-Net observations report
  31. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  32. Fermi trigger No 797039833: Global MASTER-Net observations report
  33. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  34. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 260330B: SVOM/VT further optical observation
  36. GRB 260330B: SVOM/ECLAIRs refined analysis
  37. EP260403a: LCO optical observations of the counterpart
  38. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  39. EP260403a: LCO optical counterpart detection
  40. EP260403a: COLIBRÍ optical counterpart candidate
  41. GRB 260330B: SVOM/VT optical candidate
  42. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  43. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  44. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  45. EP260324A / AT 2026hir: COLIBRÍ optical observations
  46. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  47. GRB 260402A: WINTER J-band upper limit
  48. GRB260402A: GROWTH-India Telescope optical upper limit
  49. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  50. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  51. GRB 260402A: Kilonova-Catcher optical upper limit
  52. GRB 260402A: MASTER optical observations
  53. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. Fermi GRB 260401A: Global MASTER-Net observations report
  55. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  56. EP260321a :Xinglong optical observations
  57. EP260329b: GOTO detection of optical counterpart
  58. GRB 260330B: SVOM/VT optical upper limits
  59. Konus-Wind detection of GRB 260320A
  60. GRB 260321A: SVOM/ECLAIRs refined analysis
  61. EP260329b: J-band upper limits with WINTER
  62. EP260329a: J-band upper limit with WINTER
  63. GRB 260310A: VLA Multi-frequency Radio Observations
  64. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  65. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  66. EP260329a: EP-FXT follow up observation
  67. EP260329b: Global MASTER-Net observations report
  68. Fermi trigger No 796485221: Global MASTER-Net observations report
  69. EP260329b: Optical follow-up with Kinder observations
  70. EP 260329b: COLIBRÍ optical observations
  71. EP260329a: Optical upper limit with Kinder observations
  72. EP260329b: LCO optical observations of the counterpart
  73. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  74. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  75. EP260327a: SVOM/VT optical upper limits
  76. SMA Detection of GRB 260310A / AT 2026fgk
  77. GRB 260307B: ATCA Radio Upper Limits
  78. EP260327a: WINTER J-band upper limit
  79. EP260327a: COLIBRÍ optical upper limits
  80. EP260327a: Gemini-North optical upper limits
  81. EP260324a: GROWTH-India Telescope optical observation
  82. EP260327a: Global MASTER-Net observations report
  83. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  84. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  85. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  86. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  87. EP260321a: JinShan near-infrared observations
  88. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  89. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  90. EP260321a: Gemini-South confirmation of a supernova
  91. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  92. GRB 260310A: LBT optical observations
  93. EP260321A: Mondy optical observations
  94. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  95. Fermi GRB 260323A: Global MASTER-Net observations report
  96. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  97. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  98. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  99. EP260321a: COLIBRÍ further optical observations and brightening
  100. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate

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