Skip to main content
New JavaScript client! 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 250128B: OHP/T193 optical upper limit
  2. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  3. GRB 250129A: LCO optical observations
  4. GRB 250129A: NOT optical observations and redshift confirmation
  5. GRB 250129A: GOTO optical observations show brightening afterglow
  6. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  7. Swift GRB 250129A: Global MASTER-Net observations report
  8. GRB 250128B: Enhanced Swift-XRT position
  9. The EP-WXT trigger 01709131085 is likely a flaring star
  10. Fermi GRB 250128B: Global MASTER-Net observations report
  11. GRB 250129A: Swift detection of a burst with an optical counterpart
  12. Swift GRB 250129A: Global MASTER-Net OT detection
  13. GRB 250128B: Swift-XRT refined Analysis
  14. GRB 250128B: Fermi GBM Observation
  15. GRB 250128B: GOTO optical upper limit
  16. Swift GRB 250128B: Global MASTER-Net observations report
  17. EP250125a: Upper limits from Swift/BAT-GUANO
  18. GRB 250128B: LCO optical observations
  19. GRB 250128B: Swift detection of a short burst
  20. GRB 250128B: Fermi GBM Final Real-time Localization
  21. GRB 250127A: Swift-XRT observations
  22. GRB 250127B: DDOTI Upper Limit on the Afterglow
  23. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  24. GRB 250127A: EP-FXT afterglow detection
  25. Fermi GRB 250128A: Global MASTER-Net observations report
  26. GRB 250128A: Fermi GBM Final Real-time Localization
  27. GRB 250117A: Fermi GBM Observation
  28. Fermi GRB 250127B: Global MASTER-Net observations report
  29. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  30. GRB 250127A: SVOM/VT upper limit
  31. GRB 250127B: Fermi GBM Final Real-time Localization
  32. IPN triangulation of GRB 250119C
  33. GRB 250127A: Swift ToO observations
  34. GRB 250127A: LCO optical upper limit
  35. GRB 241223A: cubesat Avion detection
  36. GRB 250127A: SVOM detection of a long burst
  37. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  38. EP250125A: Non-detection from Fermi-GBM Observations
  39. GRB 250126A: MAXI/GSC detection
  40. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  41. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  42. GRB 250126A: Fermi GBM Final Real-time Localization
  43. GECAM-A detection of a bright burst from SGR 1E1841-045
  44. GRB 250118A: Fermi GBM Observation
  45. EP250125a: Optical upper limit with Kinder observations
  46. EP250125a: REM optical counterpart detection
  47. GRB 250119C: Fermi GBM Observation
  48. EP250125a: Swift/XRT detection of a fading counterpart
  49. EP250125a: a new X-ray transient detected by Einstein Probe
  50. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  51. The EP-WXT trigger 01709130758 is a false trigger
  52. The EP-WXT trigger 01709130758 is a false trigger
  53. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  54. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  55. IPN triangulation of a bright burst from SGR 1E1841-045
  56. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  57. EP250108a: AbAO, CMO and Terskol optical upper limits
  58. Konus-Wind detection of GRB 250118B
  59. GRB 250121A: Fermi GBM Observation
  60. IPN triangulation of GRB 250118B
  61. Konus-Wind detection of GRB 250119B
  62. IPN triangulation of GRB 250119B
  63. GRB 250122A: Fermi GBM Final Real-time Localization
  64. Improved IPN triangulation of GRB 250107C
  65. GRB 250114A: Swift-BAT refined analysis
  66. GRB 250121A: INTEGRAL/SPI-ACS detection
  67. GRB 250121A: Fermi-LAT detection
  68. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  69. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  70. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  71. GRB 250121A: Fermi GBM Final Real-time Localization
  72. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  73. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  74. GRB 250119B: Fermi GBM Observation
  75. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  76. Konus-Wind detection of GRB 250117A
  77. IPN triangulation of GRB 250117A (short)
  78. ATCA detection of possible radio counterpart to GRB 250114A
  79. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  80. GRB 250119B: INTEGRAL/SPI-ACS detection
  81. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  82. EP 250108A: Late-time optical observation by LCO
  83. GRB 250117A: SVOM/GRM observation of a short burst
  84. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  85. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  86. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  87. GRB 250119C: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  89. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  90. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  91. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  92. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  93. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  94. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  95. GRB 250117A: GECAM observation of a short burst
  96. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  97. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  98. GRB 250119B: Fermi GBM Final Real-time Localization
  99. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  100. GRB 250119A: Fermi GBM Final Real-time Localization

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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