Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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"

27191 results found.

  1. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  2. IceCube Alert 260425A: Global MASTER-Net observations report
  3. Fermi trigger No 798737427: Global MASTER-Net observations report
  4. GRB 260401A: cubesat Avion detection
  5. EP260321a: Upper limits from ATCA radio observations
  6. GRB 260421B: Kilonova-Catcher optical afterglow detection
  7. The EP-WXT trigger 01709258652: Mondy optical observations
  8. EP260416a: Mondy optical observations
  9. GRB 260421B: 3.6m DOT optical observation
  10. EP260416a: ZTSh R band observations
  11. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  12. GRB 260421B: SVOM/GRM observation
  13. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  14. GRB 260421B: EP-FXT follow-up observation
  15. GOTO26djh/AT2026jpw: ATCA radio detection
  16. GRB 260421B: J-band upper limit with WINTER
  17. GRB 260421B: LCO optical counterpart detection
  18. GRB 260421B: Fermi GBM Observation
  19. GOTO26djh/AT2026jpw: radio detection at 15GHz
  20. GRB 260421B: SVOM/VT optical observations
  21. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  22. GRB 260310A: Late-time Chandra X-ray Detection
  23. EP260416a: 1.3m DFOT optical observation
  24. Fermi GRB 260421C: Global MASTER-Net observations report
  25. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  26. Fermi GRB 260421B: Global MASTER-Net observations report
  27. GRB 260421B: LCO optical afterglow confirmation
  28. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  29. GRB 260421B: TRT optical counterpart detection
  30. GRB 260421B: SVOM detection of a long burst
  31. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  32. Fermi GRB 260421A: Global MASTER-Net observations report
  33. EP260321a: VLA radio follow-up
  34. GRB 260412A: LCOGT Optical Upper Limits
  35. EP260416a: Optical follow-up observations with Kinder
  36. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  37. GRB 260417A: SVOM/GRM observation
  38. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  39. Fermi trigger No 798275385: Global MASTER-Net observations report
  40. EP260417a: GROWTH-India Telescope optical upper limit
  41. Fermi GRB 260417B: Global MASTER-Net observations report
  42. EP260417b: GROWTH-India Telescope optical upper limit
  43. EP260416a: Ondrejov D50 optical detection
  44. EP260417a: Global MASTER-Net observations report
  45. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  46. EP260416a: GMG Optical Observation
  47. Fermi GRB 260417A: Global MASTER-Net observations report
  48. EP260416a: LCO observations confirm end of flaring phase
  49. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  50. EP260417a: TRT optical counterpart detection
  51. EP260417a: Einstein Probe detection of an X-ray transient
  52. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  53. EP260417b: Einstein Probe detection of a fast X-ray transient
  54. EP260416a: KAIT optical upper limit
  55. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  56. EP260416a: WFST optical observations and rebrightening
  57. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  58. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  59. GRB 260415B: Glowbug gamma-ray detection
  60. GRB 260411B: Glowbug gamma-ray detection
  61. EP260416a: COLIBRÍ optical counterpart candidate
  62. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  63. EP260416a: Global MASTER-Net observations report
  64. EP260416a: Einstein Probe detection of an X-ray transient
  65. GOTO26djh/AT2026jpw : MASTER OT observation
  66. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  67. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  68. GRB 260415B: NuSTAR detection of long prompt emission
  69. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  70. Fermi trigger No 797912738: Global MASTER-Net observations report
  71. GRB 260414A: Glowbug gamma-ray detection
  72. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  73. EP260321a: CMO SAI J,K observations
  74. Fermi GRB 260413A: Global MASTER-Net observations report
  75. GRB 260410A: Glowbug gamma-ray detection of a short burst
  76. Fermi GRB 260412A: Global MASTER-Net observations report
  77. GRB 260412A: Fermi GBM Observation
  78. GRB 260411B: Fermi-LAT detection
  79. GRB 260411B: COLIBRÍ optical observations
  80. GRB 260410B: Fermi GBM Observation
  81. GRB260411B: 3.6m DOT optical observation
  82. GRB 260411A: SVOM/GRM observation
  83. GRB 260411B: SVOM/GRM observation of a long burst
  84. GRB 260409A: Insight-HXMT/HE detection
  85. GRB 260411B: Fermi GBM Detection
  86. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  87. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  88. GRB 260410A: COLIBRÍ optical upper limit
  89. EP-WXT01709259790: Optical Upper limits with kinder observations
  90. GRB 260410A: Fermi GBM Observation
  91. GRB 260410B: SVOM/GRM detection of a short faint burst
  92. EP-WXT01709259790: Xinglong optical upper limit
  93. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  94. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  95. EP260409a: COLIBRÍ optical upper limits
  96. EP260409a: Global MASTER-Net observations report
  97. EP260409a: Einstein Probe detection of an X-ray transient
  98. EP260321a: VLA radio detection
  99. GRB 260407A: Glowbug gamma-ray detection
  100. GRB 260402A: SVOM/ECLAIRs refined analysis

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