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').

23965 results found.

  1. EP250125A: Non-detection from Fermi-GBM Observations
  2. GRB 250126A: MAXI/GSC detection
  3. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  4. EP250125a: Optical upper limit with Kinder observations
  5. EP250125a: REM optical counterpart detection
  6. GRB 250119C: Fermi GBM Observation
  7. EP250125a: Swift/XRT detection of a fading counterpart
  8. EP250125a: a new X-ray transient detected by Einstein Probe
  9. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  10. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  11. EP250108a: AbAO, CMO and Terskol optical upper limits
  12. GRB 250121A: Fermi GBM Observation
  13. IPN triangulation of GRB 250118B
  14. IPN triangulation of GRB 250119B
  15. GRB 250114A: Swift-BAT refined analysis
  16. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  17. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  18. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  19. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  20. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  21. GRB 250119B: Fermi GBM Observation
  22. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  23. IPN triangulation of GRB 250117A (short)
  24. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  25. EP 250108A: Late-time optical observation by LCO
  26. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  27. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  28. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  29. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  30. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  31. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  33. GRB 250117A: GECAM observation of a short burst
  34. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  35. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  36. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  38. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  39. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  40. EP250108a / AT2025kg: GMG Optical Observations
  41. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  42. GRB 241217A / EP241217B: radio detection with the VLA
  43. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  44. GRB 250114B: Swift-XRT afterglow detection
  45. EP250108a: MeerKAT radio upper limit
  46. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  47. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  48. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  49. IPN triangulation of GRB 250113A
  50. GRB 250114B: Liverpool Telescope optical upper limit
  51. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  52. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  53. GRB 250114B: Swift-XRT observations
  54. GRB 250114A: LCO optical counterpart detection.
  55. GRB 250114B: OHP/T193 optical upper limit
  56. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  57. GRB 250114A: Swift-XRT refined Analysis
  58. GRB 250114A: LCOGT optical afterglow i-band detection
  59. GRB 250114B : GIT optical upper limit
  60. EP250111a: SAO RAS optical upper limit
  61. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  62. GRB 250114B: a short GRB detected with INTEGRAL
  63. GRB 250114A: Enhanced Swift-XRT position
  64. GRB 250114A: REM detection of the optical and NIR counterpart
  65. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  66. Swift GRB250114A: Global MASTER-Net OT detection
  67. GRB 250114A: LCO optical observations
  68. GRB 250114A: TRT optical observations
  69. GRB 250114A: Swift detection of a burst with an optical counterpart
  70. GRB 250101A: Terskol Zeiss-2000 optical observations
  71. EP250108a / AT 2025kg: SAO RAS optical observations
  72. EP241021a: SMA radio observation
  73. GRB 250113A: SVOM/GRM observation of a long burst
  74. GRB 250107A: VZLUSAT-2 detection
  75. EP250109b: optical upper limits with the Liverpool Telescope
  76. GRB 250106A: Swift-XRT afterglow detection
  77. EP250111a: KAIT optical observations
  78. GRB 250109A / EP250109a: Mephisto optical upper limits
  79. EP250108a: Mephisto detection
  80. EP250111a: Mondy optical observation
  81. EP250108a / AT 2025kg: LCO optical observations
  82. EP250108a / AT 2025kg: Swift UVOT detections
  83. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  84. EP250111a: NOT likely optical counterpart
  85. GRB 250101B: Fermi GBM Observation
  86. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  87. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  88. GRB 250108A: Swift/XRT afterglow fading
  89. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  90. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  91. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  92. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  93. GRB 250101A: CMO RC-500 optical observations
  94. GRB 250109A: Fermi GBM Observation
  95. EP250108a: NOT optical observations
  96. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  97. GRB 250109a: GMG Optical Upper Limit
  98. EP250109a: Swift/UVOT non-detection
  99. IPN triangulation of GRB 250107D (short/hard)
  100. EP250108a: Liverpool Telescope likely optical counterpart

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