Skip to main content
GCN at AAS 245, Legacy Circulars Address Retirement. 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').
  1. The EP-WXT trigger 01709131085 is likely a flaring star
  2. Fermi GRB 250128B: Global MASTER-Net observations report
  3. GRB 250129A: Swift detection of a burst with an optical counterpart
  4. Swift GRB250129A: Global MASTER-Net OT detection
  5. GRB 250128B: Swift-XRT refined Analysis
  6. GRB 250128B: Fermi GBM Observation
  7. GRB 250128B: GOTO optical upper limit
  8. Swift GRB 250128B: Global MASTER-Net observations report
  9. EP250125a: Upper limits from Swift/BAT-GUANO
  10. GRB 250128B: LCO optical observations
  11. GRB 250128B: Swift detection of a short burst
  12. GRB 250128B: Fermi GBM Final Real-time Localization
  13. GRB 250127A: Swift-XRT observations
  14. GRB 250127B: DDOTI Upper Limit on the Afterglow
  15. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  16. GRB 250127A: EP-FXT afterglow detection
  17. Fermi GRB 250128A: Global MASTER-Net observations report
  18. GRB 250128A: Fermi GBM Final Real-time Localization
  19. GRB 250117A: Fermi GBM Observation
  20. Fermi GRB 250127B: Global MASTER-Net observations report
  21. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  22. GRB 250127A: SVOM/VT upper limit
  23. GRB 250127B: Fermi GBM Final Real-time Localization
  24. IPN triangulation of GRB 250119C
  25. GRB 250127A: Swift ToO observations
  26. GRB 250127A: LCO optical upper limit
  27. GRB 241223A: cubesat Avion detection
  28. GRB 250127A: SVOM detection of a long burst
  29. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  30. EP250125A: Non-detection from Fermi-GBM Observations
  31. GRB 250126A: MAXI/GSC detection
  32. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  33. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  34. GRB 250126A: Fermi GBM Final Real-time Localization
  35. GECAM-A detection of a bright burst from SGR 1E1841-045
  36. GRB 250118A: Fermi GBM Observation
  37. EP250125a: Optical upper limit with Kinder observations
  38. EP250125a: REM optical counterpart detection
  39. GRB 250119C: Fermi GBM Observation
  40. EP250125a: Swift/XRT detection of a fading counterpart
  41. EP250125a: a new X-ray transient detected by Einstein Probe
  42. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  43. The EP-WXT trigger 01709130758 is a false trigger
  44. The EP-WXT trigger 01709130758 is a false trigger
  45. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  46. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  47. IPN triangulation of a bright burst from SGR 1E1841-045
  48. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  49. EP250108a: AbAO, CMO and Terskol optical upper limits
  50. Konus-Wind detection of GRB 250118B
  51. GRB 250121A: Fermi GBM Observation
  52. IPN triangulation of GRB 250118B
  53. Konus-Wind detection of GRB 250119B
  54. IPN triangulation of GRB 250119B
  55. GRB 250122A: Fermi GBM Final Real-time Localization
  56. Improved IPN triangulation of GRB 250107C
  57. GRB 250114A: Swift-BAT refined analysis
  58. GRB 250121A: INTEGRAL/SPI-ACS detection
  59. GRB 250121A: Fermi-LAT detection
  60. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  61. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  62. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  63. GRB 250121A: Fermi GBM Final Real-time Localization
  64. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  65. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  66. GRB 250119B: Fermi GBM Observation
  67. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  68. Konus-Wind detection of GRB 250117A
  69. IPN triangulation of GRB 250117A (short)
  70. ATCA detection of possible radio counterpart to GRB 250114A
  71. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  72. GRB 250119B: INTEGRAL/SPI-ACS detection
  73. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  74. EP 250108A: Late-time optical observation by LCO
  75. GRB 250117A: SVOM/GRM observation of a short burst
  76. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  77. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  78. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  79. GRB 250119C: Fermi GBM Final Real-time Localization
  80. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  81. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  82. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  83. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  84. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  85. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  86. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  87. GRB 250117A: GECAM observation of a short burst
  88. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  89. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  90. GRB 250119B: Fermi GBM Final Real-time Localization
  91. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  92. GRB 250119A: Fermi GBM Final Real-time Localization
  93. GRB 250118A: Fermi GBM Final Real-time Localization
  94. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  96. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  97. EP250108a / AT2025kg: GMG Optical Observations
  98. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  99. EP250108a / AT2025kg: VLA radio upper limit
  100. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB

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