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"
  1. GRB 251025B: SVOM/ECLAIRs refined analysis
  2. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  3. GRB 251112A: Swift/UVOT Upper Limits
  4. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  5. GRB 251112A: Swift-XRT refined Analysis
  6. GRB 251108C: AstroSat CZTI detection
  7. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  8. GRB 251112B: MAXI/GSC detection
  9. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  10. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  11. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  12. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  13. GRB 251108B: Glowbug gamma-ray detection
  14. Swift Trigger 1413695: a possible GRB 251112A
  15. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  16. Fermi trigger No 784621743: Global MASTER-Net observations report
  17. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  18. Fermi Gamma-ray Burst Monitor trigger 784653403/251112637 is not a GRB
  19. GRB251111A: 1.3m DFOT optical upper limit
  20. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  21. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  22. GRB 251111A: Swift-XRT afterglow detection
  23. GRB 251111A: SVOM/VT optical observations with X-band data
  24. SVOM GRB251111.42: Global MASTER-Net observations report
  25. GRB 251111A: Swift-XRT observations
  26. SVOM GRB251111.22: Global MASTER-Net observations report
  27. GRB 251111A: EP-FXT counterpart detection
  28. GRB 251013C: Chandra X-ray observations and jet break detection
  29. GRB 251111A: SVOM/VT optical observations with VHF data
  30. GRB 251111A: KAIT optical upper limit
  31. GRB 251111A: LCO optical observation
  32. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  33. GRB 251111A: SVOM detection of a soft burst
  34. GRB 251103B: Swift-BAT refined analysis
  35. GRB 251106A: Swift/UVOT Upper Limits
  36. GRB 251105B: Insight-HXMT/HE detection
  37. GRB 251106B: Insight-HXMT detection
  38. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  39. GRB 251105A: AstroSat CZTI detection
  40. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  41. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  42. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  43. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  44. GRB 251108A: Fermi GBM Final Localization Correction
  45. Fermi trigger No 784329591: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  47. Fermi trigger No 784279167: Global MASTER-Net observations report
  48. SVOM GRB251108.54: Global MASTER-Net observations report
  49. GRB 251102B: SVOM/GRM observation
  50. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  51. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  52. The EP-WXT trigger 01709248051 is likely a flaring star
  53. SVOM GRB251106.83: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  55. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  56. IPN triangulation of GRB 251105B (possible sGRB with EE)
  57. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  58. GRB 251106B: SVOM/GRM observation of a short burst
  59. GRB 251106A: Swift-XRT afterglow detection
  60. GRB 251106A: Kilonova-Catcher optical upper limit
  61. Fermi GBM Sub-Threshold Detection of GRB 251106A
  62. GRB 251106A: Swift/BAT arcminute localization of a burst
  63. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  64. GRB 251106A: MASTER optical observations
  65. GRB 251106A: SVOM detection of a burst
  66. GRB 251103B: AstroSat CZTI detection
  67. GRB 251025C: TERI Gamma-ray detection
  68. GRB 251016B: TERI Gamma-ray detection
  69. GRB 251016A: TERI Gamma-ray detection of a short burst
  70. GRB 250920C: TERI Gamma-ray detection
  71. Fermi trigger No 784034269: Global MASTER-Net observations report
  72. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  73. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  74. GRB 251105A: Fermi GBM Observation
  75. GRB 251105C: Fermi GBM Final Localization Correction
  76. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  77. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  78. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  79. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  80. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  81. Fermi GBM Sub-Threshold Detection of GRB 251105B
  82. GRB 251103B: Swift/UVOT Upper Limits
  83. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  84. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  85. Fermi GRB 251105A: Global MASTER-Net observations report
  86. GRB 251105A: Fermi GBM Final Real-time Localization
  87. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  88. GRB 251103B: Fermi GBM observation
  89. GRB 251104A: SVOM detection of a burst
  90. GRB 251028A: Insight-HXMT/HE detection
  91. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  92. EP251102a: FTW optical and NIR observations
  93. GRB 251103A: WFST optical observations
  94. EP251102a: update of EP-FXT follow-up observation
  95. EP251102a: OHP/T193 optical observations
  96. GRB 251103A: OHP/T193 optical observations
  97. GRB 251103A: Xinglong 2.16m optical detection
  98. GRB 251103A: Insight-HXMT detection
  99. GRB 251103A: KAIT optical observations
  100. GRB 251103B: Nanshan/HMT optical upper limit

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