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"

27194 results found.

  1. GRB 260424B: Glowbug gamma-ray detection of a short burst
  2. GRB 260424B: COLIBRÍ optical upper limit
  3. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  4. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  5. IceCube Alert 260425A: Global MASTER-Net observations report
  6. Fermi trigger No 798737427: Global MASTER-Net observations report
  7. GRB 260401A: cubesat Avion detection
  8. EP260321a: Upper limits from ATCA radio observations
  9. GRB 260421B: Kilonova-Catcher optical afterglow detection
  10. The EP-WXT trigger 01709258652: Mondy optical observations
  11. EP260416a: Mondy optical observations
  12. GRB 260421B: 3.6m DOT optical observation
  13. EP260416a: ZTSh R band observations
  14. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  15. GRB 260421B: SVOM/GRM observation
  16. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  17. GRB 260421B: EP-FXT follow-up observation
  18. GOTO26djh/AT2026jpw: ATCA radio detection
  19. GRB 260421B: J-band upper limit with WINTER
  20. GRB 260421B: LCO optical counterpart detection
  21. GRB 260421B: Fermi GBM Observation
  22. GOTO26djh/AT2026jpw: radio detection at 15GHz
  23. GRB 260421B: SVOM/VT optical observations
  24. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  25. GRB 260310A: Late-time Chandra X-ray Detection
  26. EP260416a: 1.3m DFOT optical observation
  27. Fermi GRB 260421C: Global MASTER-Net observations report
  28. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  29. Fermi GRB 260421B: Global MASTER-Net observations report
  30. GRB 260421B: LCO optical afterglow confirmation
  31. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  32. GRB 260421B: TRT optical counterpart detection
  33. GRB 260421B: SVOM detection of a long burst
  34. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  35. Fermi GRB 260421A: Global MASTER-Net observations report
  36. EP260321a: VLA radio follow-up
  37. GRB 260412A: LCOGT Optical Upper Limits
  38. EP260416a: Optical follow-up observations with Kinder
  39. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  40. GRB 260417A: SVOM/GRM observation
  41. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  42. Fermi trigger No 798275385: Global MASTER-Net observations report
  43. EP260417a: GROWTH-India Telescope optical upper limit
  44. Fermi GRB 260417B: Global MASTER-Net observations report
  45. EP260417b: GROWTH-India Telescope optical upper limit
  46. EP260416a: Ondrejov D50 optical detection
  47. EP260417a: Global MASTER-Net observations report
  48. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  49. EP260416a: GMG Optical Observation
  50. Fermi GRB 260417A: Global MASTER-Net observations report
  51. EP260416a: LCO observations confirm end of flaring phase
  52. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  53. EP260417a: TRT optical counterpart detection
  54. EP260417a: Einstein Probe detection of an X-ray transient
  55. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  56. EP260417b: Einstein Probe detection of a fast X-ray transient
  57. EP260416a: KAIT optical upper limit
  58. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  59. EP260416a: WFST optical observations and rebrightening
  60. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  61. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  62. GRB 260415B: Glowbug gamma-ray detection
  63. GRB 260411B: Glowbug gamma-ray detection
  64. EP260416a: COLIBRÍ optical counterpart candidate
  65. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  66. EP260416a: Global MASTER-Net observations report
  67. EP260416a: Einstein Probe detection of an X-ray transient
  68. GOTO26djh/AT2026jpw : MASTER OT observation
  69. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  70. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  71. GRB 260415B: NuSTAR detection of long prompt emission
  72. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  73. Fermi trigger No 797912738: Global MASTER-Net observations report
  74. GRB 260414A: Glowbug gamma-ray detection
  75. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  76. EP260321a: CMO SAI J,K observations
  77. Fermi GRB 260413A: Global MASTER-Net observations report
  78. GRB 260410A: Glowbug gamma-ray detection of a short burst
  79. Fermi GRB 260412A: Global MASTER-Net observations report
  80. GRB 260412A: Fermi GBM Observation
  81. GRB 260411B: Fermi-LAT detection
  82. GRB 260411B: COLIBRÍ optical observations
  83. GRB 260410B: Fermi GBM Observation
  84. GRB260411B: 3.6m DOT optical observation
  85. GRB 260411A: SVOM/GRM observation
  86. GRB 260411B: SVOM/GRM observation of a long burst
  87. GRB 260409A: Insight-HXMT/HE detection
  88. GRB 260411B: Fermi GBM Detection
  89. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  90. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  91. GRB 260410A: COLIBRÍ optical upper limit
  92. EP-WXT01709259790: Optical Upper limits with kinder observations
  93. GRB 260410A: Fermi GBM Observation
  94. GRB 260410B: SVOM/GRM detection of a short faint burst
  95. EP-WXT01709259790: Xinglong optical upper limit
  96. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  97. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  98. EP260409a: COLIBRÍ optical upper limits
  99. EP260409a: Global MASTER-Net observations report
  100. EP260409a: Einstein Probe detection of an X-ray transient

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