Skip to main content
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  2. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  3. GRB 250117A: GECAM observation of a short burst
  4. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  5. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  6. GRB 250119B: Fermi GBM Final Real-time Localization
  7. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  8. GRB 250119A: Fermi GBM Final Real-time Localization
  9. GRB 250118A: Fermi GBM Final Real-time Localization
  10. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  11. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  12. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  13. EP250108a / AT2025kg: GMG Optical Observations
  14. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  15. EP250108a / AT2025kg: VLA radio upper limit
  16. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  17. Konus-Wind detection of GRB 250116A
  18. GRB 250116A: GECAM-B detection of a long burst
  19. GRB 241217A / EP241217B: radio detection with the VLA
  20. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  21. Swift Trigger 1282245 is not a GRB
  22. GRB 250116A: Fermi-LAT detection
  23. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  24. GRB 250114B: Swift-XRT afterglow detection
  25. GRB 250114B: SVOM/VT upper limit
  26. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  27. EP250108a: MeerKAT radio upper limit
  28. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  29. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  30. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  31. Konus-Wind detection of GRB 250113A
  32. IPN triangulation of GRB 250113A
  33. GRB 250114B: Liverpool Telescope optical upper limit
  34. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  35. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  36. GRB 250114B: Swift-XRT observations
  37. GRB 250114A: LCO optical counterpart detection.
  38. GRB 250114B: OHP/T193 optical upper limit
  39. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  40. GRB 250114A: Swift-XRT refined Analysis
  41. Integral GRB250114.55: Global MASTER-Net observations report
  42. GRB 250114A: LCOGT optical afterglow i-band detection
  43. GRB 250114B : GIT optical upper limit
  44. GRB 250114B: Swift ToO observations
  45. EP250111a: SAO RAS optical upper limit
  46. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  47. GRB 250114B: a short GRB detected with INTEGRAL
  48. EP250108a: correction to GCN 38908
  49. GRB 250114A: Enhanced Swift-XRT position
  50. GRB 250113A: INTEGRAL/SPI-ACS detection
  51. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  52. GRB 250114A: REM detection of the optical and NIR counterpart
  53. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  54. Swift GRB250114A: Global MASTER-Net OT detection
  55. GRB 250114A: LCO optical observations
  56. GRB 250114A: TRT optical observations
  57. Swift GRB 250114A: Global MASTER-Net observations report
  58. GRB 250114A: Swift detection of a burst with an optical counterpart
  59. GRB 250101A: Terskol Zeiss-2000 optical observations
  60. EP250108a / AT 2025kg: SAO RAS optical observations
  61. EP241021a: SMA radio observation
  62. GRB 250113A: SVOM/GRM observation of a long burst
  63. GRB 250107A: VZLUSAT-2 detection
  64. EP250109b: optical upper limits with the Liverpool Telescope
  65. GRB 250109A / EP250109a: GRBAlpha detection
  66. GRB 250107D: GRBAlpha detection
  67. GRB 250106A: Swift-XRT afterglow detection
  68. Fermi trigger No 758442826: Global MASTER-Net observations report
  69. EP250111a: KAIT optical observations
  70. GRB 250109A / EP250109a: Mephisto optical upper limits
  71. EP250108a: Mephisto detection
  72. EP250111a: Mondy optical observation
  73. EP250108a / AT 2025kg: LCO optical observations
  74. EP250111a: Global MASTER-Net observations report
  75. EP250111a: Swift/XRT detection and fading
  76. EP250108a / AT 2025kg: Swift UVOT detections
  77. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  78. EP250108a: optical follow-up observations with the Liverpool Telescope
  79. EP250111a: NOT likely optical counterpart
  80. EP250111a: a new X-ray transient detected by Einstein Probe
  81. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  82. GRB 250101B: Fermi GBM Observation
  83. EP250108a: further NOT optical observations
  84. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  85. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  86. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  87. GRB 250108A: Swift/XRT afterglow fading
  88. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  89. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  90. Konus-Wind detection of GRB 250107C
  91. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  92. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  93. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  94. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  95. GRB 250101A: CMO RC-500 optical observations
  96. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  97. EP250108a: EP-FXT follow-up observation
  98. GRB 250109A: Fermi GBM Observation
  99. The EP-WXT trigger 01709130111 is likely a flaring star
  100. EP250108a: NOT optical observations

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