Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

27392 results found.

  1. EP260806a: OSIRIS+/GTC redshift z=0.089
  2. EP260806a: LCO likely optical counterpart
  3. SN 2026stf / GRB 260708A: ATLAS forced photometry
  4. Fermi GRB 260805A: Global MASTER-Net observations report
  5. GRB 260805B: Fermi GBM Final Localization
  6. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  7. GRB 260805A: Fermi GBM Final Localization
  8. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  9. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  10. GRB 260804A: Fermi GBM Final Real-time Localization
  11. GRB 260708A: LCO further optical observations show supernova features
  12. GRB 260803A: Fermi GBM Final Real-time Localization
  13. Fermi GRB 260802B: Global MASTER-Net observations report
  14. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  15. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  16. GRB 260802A: SVOM/VT optical upper limits from VHF data
  17. GRB 260802A: LCO optical upper limits
  18. GRB 260802B: Fermi GBM Final Localization
  19. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  20. The EP-WXT trigger 01709277420 is likely a flaring star
  21. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  22. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  23. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  24. GRB 260731A: AstroSat CZTI detection of a long burst
  25. EP260731a: COLIBRÍ optical upper limit
  26. EP260731a: NOT optical upper limit
  27. GRB 260727A: SVOM/ECLAIRs refined analysis
  28. GRB 260726A: SVOM/ECLAIRs refined analysis
  29. GRB260730A: Fermi GBM Final Localization
  30. EP260728a: COLIBRÍ optical upper limit
  31. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  32. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  33. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  34. GRB 260727A: AbAO and SAO RAS optical observations
  35. EP260728a: EP-FXT follow-up observation
  36. GRB 260726A: EP-FXT follow-up observations
  37. GRB 260726A: Fermi GBM Observation
  38. EP260727a: 1.5m OSN optical counterpart detection
  39. EP260727a: OHP/T193 optical observations
  40. GRB 260726A: Liverpool Telescope optical observations
  41. GRB 260727A: Liverpool Telescope optical upper limits
  42. EP260727a: NUTTELA-TAO Early Optical Limits
  43. GRB 260728A: Fermi GBM Final Localization
  44. GRB 260727A: EP/FXT follow-up observations
  45. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  46. GRB 260726A: J-band upper limit with WINTER
  47. GRB 260727A: J-band upper limit with WINTER
  48. GRB 260726A: SVOM/VT optical candidate
  49. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  50. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  51. EP260723a: SVOM/ECLAIRs Upper Limit
  52. GRB 260727A: GOTO early optical upper limit
  53. GRB 260727A: LCO optical upper limits
  54. GRB 260727B: Fermi GBM Final Real-time Localization
  55. Fermi GRB 260726A: Global MASTER-Net observations report
  56. GRB 260727A: SVOM detection of a bright long burst
  57. GRB 260726A: SVOM detection of a burst
  58. GRB 260726A: Fermi GBM Final Real-time Localization
  59. GRB 260718A: SVOM/ECLAIRs refined analysis
  60. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  61. EP260723a: SVOM/VT optical observation
  62. EP260723a: COLIBRÍ optical observations
  63. EP260723a: NOT optical conterpart confirmation
  64. EP260723a: EP-WXT detection of a fast X-ray transient
  65. GRB 260723A: Fermi GBM Final Localization
  66. IceCube Alert 260722A: Global MASTER-Net observations report
  67. GRB 260722A: Fermi GBM Final Real-time Localization
  68. Fermi GBM trigger 806384210/260722151 is not a GRB
  69. GRB 260721A: NuSTAR detection of prompt emission
  70. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  71. GRB 260705A: Retraction of optical counterpart
  72. GRB 260718A: EP-FXT follow-up observation
  73. Fermi trigger No 806104130: Global MASTER-Net observations report
  74. Fermi GRB 260718A: Global MASTER-Net observations report
  75. GRB 260718A: LCO optical upper limits
  76. GRB 260718A: Fermi GBM Observation
  77. GRB 260718A: SVOM/VT optical upper limits
  78. GRB 260718A: SVOM/VT optical upper limits from VHF data
  79. GRB 260718A: SVOM detection of a burst
  80. GRB 260618B: EP-FXT follow-up observation upper limit
  81. GRB 260714B: COLIBRÍ optical counterpart candidate
  82. SVOM sb26071506: Global MASTER-Net observations report
  83. sb26071506: SVOM detection of a X-ray transient
  84. GRB 260715A: Fermi GBM Final Real-time Localization
  85. EP260703a: SVOM/ECLAIRs Upper Limit
  86. GRB 260714B: Fermi-LAT detection
  87. GRB 260714B: Fermi GBM Detection
  88. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  89. GRB 260714B: Fermi GBM Final Real-time Localization
  90. GRB 260714A: Fermi GBM Final Real-time Localization
  91. GRB 260619A: SVOM/VT continuous optical observations
  92. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  93. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  94. GRB 260708A: GRANDMA Optical Observations
  95. GRB 260708A: LCO optical observations
  96. GRB 260710A: Fermi GBM Detection
  97. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  98. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  99. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  100. GRB 260710A: Fermi GBM Final Real-time Localization

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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