Skip to main content
Circulars over Kafka event name backfill. 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"

24700 results found.

  1. GRB 250128B: VLA radio upper limit
  2. Ep250125A: 1.3m DFOT optical upper limit
  3. GRB 250129A: Skynet optical observations
  4. GRB 250129A: Swift-XRT refined Analysis
  5. GRB 250128B: Gemini-North optical extended source detection
  6. GRB 250128B: TNG optical upper limit
  7. GRB 250129A: Swift/UVOT Detection
  8. GRB 250128B: VLT/HAWKI near-infrared observations
  9. GRB 250127A: CrAO and Terskol optical upper limits
  10. GRB 250129A: Enhanced Swift-XRT position
  11. GRB 250128B: NOT optical upper limit
  12. GRB 250128B: VLT/FORS2 optical observations
  13. GRB 250129A: REM optical/NIR afterglow detection
  14. GRB 250129A: OHP/T193 optical and spectroscopy observations
  15. GRB 250129A: Early afterglow detection by LCO.
  16. GRB 250128B: OHP/T193 optical upper limit
  17. GRB 250129A: LCO optical observations
  18. GRB 250128B: Enhanced Swift-XRT position
  19. GRB 250129A: Swift detection of a burst with an optical counterpart
  20. Swift GRB 250129A: Global MASTER-Net OT detection
  21. GRB 250128B: Swift-XRT refined Analysis
  22. GRB 250128B: GOTO optical upper limit
  23. EP250125a: Upper limits from Swift/BAT-GUANO
  24. GRB 250128B: LCO optical observations
  25. GRB 250128B: Swift detection of a short burst
  26. GRB 250127A: Swift-XRT observations
  27. GRB 250127B: DDOTI Upper Limit on the Afterglow
  28. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  29. Fermi GRB 250128A: Global MASTER-Net observations report
  30. GRB 250117A: Fermi GBM Observation
  31. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  32. IPN triangulation of GRB 250119C
  33. GRB 250127A: LCO optical upper limit
  34. GRB 241223A: cubesat Avion detection
  35. EP250125A: Non-detection from Fermi-GBM Observations
  36. GRB 250126A: MAXI/GSC detection
  37. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  38. EP250125a: Optical upper limit with Kinder observations
  39. EP250125a: REM optical counterpart detection
  40. GRB 250119C: Fermi GBM Observation
  41. EP250125a: Swift/XRT detection of a fading counterpart
  42. EP250125a: a new X-ray transient detected by Einstein Probe
  43. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  44. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  45. EP250108a: AbAO, CMO and Terskol optical upper limits
  46. GRB 250121A: Fermi GBM Observation
  47. IPN triangulation of GRB 250118B
  48. IPN triangulation of GRB 250119B
  49. GRB 250114A: Swift-BAT refined analysis
  50. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  51. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  52. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  53. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  54. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  55. GRB 250119B: Fermi GBM Observation
  56. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  57. IPN triangulation of GRB 250117A (short)
  58. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  59. EP 250108A: Late-time optical observation by LCO
  60. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  61. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  62. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  63. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  64. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  65. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  67. GRB 250117A: GECAM observation of a short burst
  68. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  69. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  70. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  71. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  73. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  74. EP250108a / AT2025kg: GMG Optical Observations
  75. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  76. GRB 241217A / EP241217B: radio detection with the VLA
  77. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  78. GRB 250114B: Swift-XRT afterglow detection
  79. EP250108a: MeerKAT radio upper limit
  80. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  81. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  82. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  83. IPN triangulation of GRB 250113A
  84. GRB 250114B: Liverpool Telescope optical upper limit
  85. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  86. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  87. GRB 250114B: Swift-XRT observations
  88. GRB 250114A: LCO optical counterpart detection.
  89. GRB 250114B: OHP/T193 optical upper limit
  90. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  91. GRB 250114A: Swift-XRT refined Analysis
  92. GRB 250114A: LCOGT optical afterglow i-band detection
  93. GRB 250114B : GIT optical upper limit
  94. EP250111a: SAO RAS optical upper limit
  95. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  96. GRB 250114B: a short GRB detected with INTEGRAL
  97. GRB 250114A: Enhanced Swift-XRT position
  98. GRB 250114A: REM detection of the optical and NIR counterpart
  99. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  100. Swift GRB250114A: Global MASTER-Net OT detection

Advanced

Download all Circulars as a .tar.gz archive:
Looking for U.S. government information and services? Visit USA.gov