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"

15693 results found.

  1. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  2. sb26021801: SVOM detection of a long faint X-ray transient
  3. EP-WXT 01709258455: NOT optical upper limits
  4. EP260214b: Mondy optical observations
  5. EP260214b: 1.3m DFOT optical upper limit
  6. EP260210a: Mondy optical upper limits
  7. GRB 260208A: AbAO and Terskol optical upper limits
  8. GRB 260208A: continued Mondy optical observations
  9. EP260214b: Liverpool Telescope optical observations
  10. EP260214b: Optical upper limit with Kinder observations
  11. EP260214a: Optical upper limits with Kinder observations
  12. EP260214b: EP-FXT follow-up observation
  13. EP260214b: DDOTI Optical Detection
  14. EP260214b: GROWTH-India Telescope optical upper limit
  15. EP260214b: SVOM/VT optical observation
  16. EP260214a: NOT optical upper limits
  17. EP260214a: COLIBRÍ optical upper limits
  18. EP260214b: OHP/T120 optical observations
  19. EP260214b: LCO optical counterpart detection
  20. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  21. GRB 260211A: SVOM/VT optical counterpart
  22. EP260214b: COLIBRÍ optical observations
  23. EP260214a: SVOM/VT optical upper limits
  24. EP260214b: NOT optical counterpart detection
  25. EP260213a: Liverpool Telescope optical upper limits
  26. EP260213a: COLIBRÍ optical upper limits
  27. EP260213a: Optical upper limits with Kinder observations
  28. EP260213a: SVOM/VT optical upper limit
  29. EP260213a: Mondy R-band optical upper limit
  30. EP260213a: NUTTelA-TAO Early Optical Limits
  31. EP/WXT 01709258378: NOT optical upper limits
  32. GRB 260212A: SVOM/GRM observation of a long burst
  33. GRB 260211A: SVOM/VT optical observation
  34. GRB 260211A: GOTO optical upper limit
  35. GRB 260211A: LAST optical upper limit
  36. GRB 260210A: SVOM/GRM observation
  37. GRB 260211A: LCO optical upper limits
  38. GRB260131A/B: 3.6m DOT Optical Observations
  39. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  40. GRB 260211A: SVOM detection of a burst
  41. EP260209a: COLIBRÍ optical upper limit
  42. EP260209a: LCO optical upper limits
  43. GRB 260208A: LCO detection of the optical counterpart
  44. EP260210a: Optical upper limits with Kinder observations
  45. EP260210a: SVOM/VT optical upper limit
  46. EP260210a: COLIBRÍ optical upper limit
  47. GRB 260208C: SVOM/GRM observation
  48. GRB 260204A: Swift-XRT afterglow detection
  49. GRB260208A: Liverpool Telescope optical follow-up observations
  50. GRB 260208A: NuSTAR detection of prompt emission
  51. GRB 260131A/B: continued Mondy optical observations
  52. GRB 260208B: COLIBRÍ optical observations
  53. GRB 260208A: Mondy optical observations (duplicate submission)
  54. GRB 260208A: Mondy optical observations
  55. GRB 260208A: 1.3m DFOT optical detection
  56. GRB 260208A: COLIBRÍ optical observations
  57. GRB 260208B: EP-FXT observation
  58. GRB 260208A: NOT spectroscopic redshift z = 2.36
  59. GRB 260208A: Liverpool Telescope optical detection
  60. GRB 260208B: SVOM/VT optical candidate
  61. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  62. GRB 260208A: SVOM/VT optical observation
  63. GRB 260208A: Swift-XRT observations
  64. GRB 260208B: SVOM/GRM observation of a bright burst
  65. GRB 260208A: Fermi GBM Classification Correction
  66. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  67. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  68. GRB 260207A : MASTER optical counterpart discovery
  69. GRB 260131A/B: Mondy and Terskol optical observations
  70. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  71. GRB 260204A: Swift-XRT observations
  72. GRB 260204A: LCO optical afterglow detection
  73. GRB 260204A: SVOM/VT optical candidate
  74. GRB 260204A : MASTER Global robotic net optical observations
  75. GRB 260204A: GOTO optical upper limit
  76. GRB 260204A: LCO optical upper limits
  77. GRB 260131A/B: OHP/T193 optical observations
  78. GRB 260131A: KAIT optical observations
  79. GRB 251230A: MeerLICHT afterglow detection
  80. GRB 260131A: FTW optical and NIR observations
  81. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  82. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  83. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  84. GRB 260131A/B: EP/FXT X-ray afterglow detection
  85. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  86. GRB 260131A: NOT spectroscopic redshift z = 1.434
  87. EP260131a: Liverpool Telescope optical upper limits
  88. EP260131a: COLIBRÍ further observations
  89. EP260131a: SVOM/VT optical observation
  90. EP260131a: Xinglong optical upper limit
  91. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  92. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  93. EP260131a: COLIBRÍ observations of slow optical fading
  94. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  95. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  96. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  97. EP260131a: COLIBRÍ optical observations of the counterpart
  98. EP260131a: Las Cumbres detection of an optical counterpart
  99. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  100. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits

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