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"

27187 results found.

  1. EP260321a: Upper limits from ATCA radio observations
  2. GRB 260421B: Kilonova-Catcher optical afterglow detection
  3. The EP-WXT trigger 01709258652: Mondy optical observations
  4. EP260416a: Mondy optical observations
  5. GRB 260421B: 3.6m DOT optical observation
  6. EP260416a: ZTSh R band observations
  7. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 260421B: SVOM/GRM observation
  9. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  10. GRB 260421B: EP-FXT follow-up observation
  11. GOTO26djh/AT2026jpw: ATCA radio detection
  12. GRB 260421B: J-band upper limit with WINTER
  13. GRB 260421B: LCO optical counterpart detection
  14. GRB 260421B: Fermi GBM Observation
  15. GOTO26djh/AT2026jpw: radio detection at 15GHz
  16. GRB 260421B: SVOM/VT optical observations
  17. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  18. GRB 260310A: Late-time Chandra X-ray Detection
  19. EP260416a: 1.3m DFOT optical observation
  20. Fermi GRB 260421C: Global MASTER-Net observations report
  21. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  22. Fermi GRB 260421B: Global MASTER-Net observations report
  23. GRB 260421B: LCO optical afterglow confirmation
  24. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  25. GRB 260421B: TRT optical counterpart detection
  26. GRB 260421B: SVOM detection of a long burst
  27. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  28. Fermi GRB 260421A: Global MASTER-Net observations report
  29. EP260321a: VLA radio follow-up
  30. GRB 260412A: LCOGT Optical Upper Limits
  31. EP260416a: Optical follow-up observations with Kinder
  32. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  33. GRB 260417A: SVOM/GRM observation
  34. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  35. Fermi trigger No 798275385: Global MASTER-Net observations report
  36. EP260417a: GROWTH-India Telescope optical upper limit
  37. Fermi GRB 260417B: Global MASTER-Net observations report
  38. EP260417b: GROWTH-India Telescope optical upper limit
  39. EP260416a: Ondrejov D50 optical detection
  40. EP260417a: Global MASTER-Net observations report
  41. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  42. EP260416a: GMG Optical Observation
  43. Fermi GRB 260417A: Global MASTER-Net observations report
  44. EP260416a: LCO observations confirm end of flaring phase
  45. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  46. EP260417a: TRT optical counterpart detection
  47. EP260417a: Einstein Probe detection of an X-ray transient
  48. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  49. EP260417b: Einstein Probe detection of a fast X-ray transient
  50. EP260416a: KAIT optical upper limit
  51. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  52. EP260416a: WFST optical observations and rebrightening
  53. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  54. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  55. GRB 260415B: Glowbug gamma-ray detection
  56. GRB 260411B: Glowbug gamma-ray detection
  57. EP260416a: COLIBRÍ optical counterpart candidate
  58. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  59. EP260416a: Global MASTER-Net observations report
  60. EP260416a: Einstein Probe detection of an X-ray transient
  61. GOTO26djh/AT2026jpw : MASTER OT observation
  62. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  63. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  64. GRB 260415B: NuSTAR detection of long prompt emission
  65. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  66. Fermi trigger No 797912738: Global MASTER-Net observations report
  67. GRB 260414A: Glowbug gamma-ray detection
  68. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  69. EP260321a: CMO SAI J,K observations
  70. Fermi GRB 260413A: Global MASTER-Net observations report
  71. GRB 260410A: Glowbug gamma-ray detection of a short burst
  72. Fermi GRB 260412A: Global MASTER-Net observations report
  73. GRB 260412A: Fermi GBM Observation
  74. GRB 260411B: Fermi-LAT detection
  75. GRB 260411B: COLIBRÍ optical observations
  76. GRB 260410B: Fermi GBM Observation
  77. GRB260411B: 3.6m DOT optical observation
  78. GRB 260411A: SVOM/GRM observation
  79. GRB 260411B: SVOM/GRM observation of a long burst
  80. GRB 260409A: Insight-HXMT/HE detection
  81. GRB 260411B: Fermi GBM Detection
  82. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  83. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  84. GRB 260410A: COLIBRÍ optical upper limit
  85. EP-WXT01709259790: Optical Upper limits with kinder observations
  86. GRB 260410A: Fermi GBM Observation
  87. GRB 260410B: SVOM/GRM detection of a short faint burst
  88. EP-WXT01709259790: Xinglong optical upper limit
  89. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  90. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  91. EP260409a: COLIBRÍ optical upper limits
  92. EP260409a: Global MASTER-Net observations report
  93. EP260409a: Einstein Probe detection of an X-ray transient
  94. EP260321a: VLA radio detection
  95. GRB 260407A: Glowbug gamma-ray detection
  96. GRB 260402A: SVOM/ECLAIRs refined analysis
  97. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  98. EP260402a / GRB 260402A: Mephisto optical upper limits
  99. EP-WXT01709259586: Xinglong optical upper limit
  100. EP260403a: Mephisto optical 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