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"

3533 results found.

  1. EP250905b: Global MASTER-Net observations report
  2. EP250905b: EP-WXT detection of a fast X-ray transient
  3. EP250905a: FTW one optical and multiple NIR counterpart candidates
  4. EP250905a: JinShan likely optical counterpart detection
  5. IceCube Alert 250905.84: Global MASTER-Net observations report
  6. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  7. Fermi GRB 250902B: Global MASTER-Net observations report
  8. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  9. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 250831A: Swift-XRT counterpart detection
  11. GRB 250831A: SVOM detection of a soft burst
  12. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  13. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  14. EP250828a: KAIT optical upper limit
  15. EP250828a: Seimei/TriCCS optical counterpart detection
  16. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  17. EP250827a: LCO observations show fading optical counterpart
  18. GRB 250828A: Fermi GBM Final Localization
  19. EP250827a: Global MASTER-Net observations report
  20. Fermi GRB 250824B: Global MASTER-Net observations report
  21. GRB 250823A: SVOM/VT optical observation
  22. GRB 250823A: BOOTES6/DPRT early optical detection
  23. GRB 250821A: Prompt enhanced Swift-XRT position
  24. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  25. Fermi trigger No 776849714: Global MASTER-Net observations report
  26. GRB 250812A: NTT spectroscopic redshift z = 2.57
  27. IceCube Alert 250813.14: Global MASTER-Net observations report
  28. GRB 250702B: Chandra X-ray Detection
  29. Fermi GRB 250808A: Global MASTER-Net observations report
  30. Konus-Wind detection of GRB 250807A
  31. GRB 250805A: Kilonova-Catcher optical upper limits
  32. GRB 250804B: Swift-XRT observations
  33. GRB 250804B: SVOM/GRM observation of a short burst
  34. EP250711a: CrAO and Assy optical observations
  35. EP250730a: Global MASTER-Net observations report
  36. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  37. GRB 250725A: AstroSat CZTI detection
  38. GRB 250728A: Fermi GBM Observation
  39. Fermi trigger No 775387550: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  41. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  42. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  43. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  44. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  45. GRB 250721A: MAXI/GSC detection
  46. Fermi trigger No 774730635: Global MASTER-Net observations report
  47. Swift GRB250718.01: Global MASTER-Net observations report
  48. GRB 250711A: DDOTI Optical Upper Limit
  49. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  50. EP250711a: NOT optical counterpart candidate
  51. Fermi GRB 250711A: Global MASTER-Net observations report
  52. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  53. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  54. EP250704a / GRB 250704B - REM observations
  55. Fermi GRB 250702E: Global MASTER-Net observations report
  56. Fermi GRB 250702B: Global MASTER-Net observations report
  57. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  58. Fermi GRB 250702F: Global MASTER-Net observations report
  59. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  60. GRB 250628A: REM optical/NIR upper limits
  61. GRB 250628C: Fermi GBM Final Real-time Localization
  62. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  63. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  64. GRB 250628A: VLT/X-shooter upper limits
  65. Fermi GRB 250626A: Global MASTER-Net observations report
  66. Swift GRB 250628A: Global MASTER-Net observations report
  67. GRB 250625A: SVOM/C-GFT upper limit in early phase
  68. GRB 250625A: OHP/T193 optical detection
  69. Swift GRB 250625A: Global MASTER-Net observations report
  70. Fermi GRB 250623A: Global MASTER-Net observations report
  71. Fermi trigger No 772190032: Global MASTER-Net observations report
  72. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  73. Fermi trigger No 772058337: Global MASTER-Net observations report
  74. GRB 250617B: SAO RAS optical observations
  75. Fermi trigger No 771752663: Global MASTER-Net observations report
  76. Fermi trigger No 771424081: Global MASTER-Net observations report
  77. EP250612a: Einstein Probe detection of an X-ray transient
  78. Swift GRB250612.04: Global MASTER-Net observations report
  79. Fermi trigger No 771072240: Global MASTER-Net observations report
  80. GRB 250527C: CrAO Optical Upper Limit
  81. GRB 250606A: Fermi GBM Final Real-time Localization
  82. Fermi trigger No 770867684: Global MASTER-Net observations report
  83. GRB 250605A: LT optical observations
  84. Fermi GRB 250531A: Global MASTER-Net observations report
  85. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  86. Fermi trigger No 770058372: Global MASTER-Net observations report
  87. GRB 250314A: CIDER NB1008 upper limit
  88. EP250526a: Einstein Probe detection of a fast X-ray transient
  89. Fermi GRB 250516A: Global MASTER-Net observations report
  90. Konus-Wind detection of GRB 250506A
  91. EP250511a: COLIBRÍ optical counterpart candidate
  92. Fermi GRB 250510C: Global MASTER-Net observations report
  93. Fermi GRB 250510B: Global MASTER-Net observations report
  94. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. GRB 250506A: Swift-XRT observations
  96. Fermi GRB 250504A: Global MASTER-Net observations report
  97. Fermi trigger No 767975731: Global MASTER-Net observations report
  98. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  99. EP250428b: SAO RAS optical upper limit
  100. EP250427a / GRB 250427A: OHP/T193 photometric 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