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. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  2. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  4. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  5. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  6. GRB 250628A: REM optical/NIR upper limits
  7. GRB 250628C: Fermi GBM Final Real-time Localization
  8. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  9. GRB 250628B: SVOM detection of a long burst
  10. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  11. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  12. GRB 250628A: VLT/X-shooter upper limits
  13. GRB 250628A: Swift/UVOT Upper Limits
  14. GRB 250628A: Swift-XRT refined Analysis
  15. Fermi GRB 250626A: Global MASTER-Net observations report
  16. Swift GRB 250628A: Global MASTER-Net observations report
  17. GRB 250628A: Enhanced Swift-XRT position
  18. GRB 250628A: Swift detection of a burst
  19. GRB 250625A: Swift-BAT refined analysis
  20. GRB 250625A: Leavitt Observatory afterglow detection
  21. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  22. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  23. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  24. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  25. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  26. GRB 250626A: Fermi GBM Final Real-time Localization
  27. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  28. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  29. GRB 250625A: SVOM/C-GFT upper limit in early phase
  30. GRB 250625A: GECAM-B detection
  31. GRB 250625A: Swift/UVOT Upper Limits
  32. GRB 250625A: ABObservatory afterglow detection
  33. GRB 250625A: OHP/T193 optical detection
  34. GRB 250625A: COLIBRÍ optical observations
  35. GRB 250625A: Fermi-LAT detection
  36. GRB 250625A: Swift-XRT refined Analysis
  37. GRB 250625A: JinShan optical observations
  38. GRB250625A: Fermi GBM Observation
  39. Swift GRB 250625A: Global MASTER-Net observations report
  40. GRB 250625A: NOT z-band upper limit
  41. GRB 250625A: SVOM/VT optical confirmation
  42. GRB 250620B: Fermi GBM Observation
  43. GRB 250625A: SAO RAS possible optical afterglow
  44. GRB 250625A: Enhanced Swift-XRT position
  45. Fermi GRB 250625A: Global MASTER-Net observations report
  46. GRB 250625A: Swift detection of a burst
  47. GRB 250625A: Fermi GBM Final Real-time Localization
  48. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  49. GRB 250620A: AstroSat CZTI detection
  50. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  51. GRB 241018A: Maidanak optical observations
  52. GRB 250620C: AstroSat CZTI detection
  53. Fermi GRB 250624A: Global MASTER-Net observations report
  54. GRB 250624A: Fermi GBM Final Real-time Localization
  55. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  56. Fermi GRB 250623A: Global MASTER-Net observations report
  57. GRB 250623A: Fermi GBM Final Real-time Localization
  58. GRB 250521A: VZLUSAT-2 detection
  59. GRB 250617B: Swift-BAT refined analysis
  60. Fermi trigger No 772190032: Global MASTER-Net observations report
  61. Konus-Wind detection of GRB 250620C
  62. IPN triangulation of GRB 250620С (long/bright)
  63. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  64. GRB 250620C: SVOM/GRM observation
  65. GRB 250620A: SVOM/GRM observation of a short burst
  66. GRB250620A: Fermi GBM Observation
  67. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  68. Fermi GRB 250621A: Global MASTER-Net observations report
  69. GRB 250619B: Fermi GBM Observation
  70. GRB 250621A: Fermi GBM Final Real-time Localization
  71. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  72. GRB250620C: Fermi GBM Observation
  73. GRB 250506A - SVOM/ECLAIRs Refined analysis
  74. The EP-WXT trigger 01709179071 is likely a flaring star
  75. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  76. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  77. GRB 250620C: Fermi GBM Final Real-time Localization
  78. Fermi trigger No 772128434: Global MASTER-Net observations report
  79. GRB 250620B: Fermi GBM Final Real-time Localization
  80. GRB 250620A: Fermi GBM Final Real-time Localization
  81. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  82. GRB 250617B: Nickel telescope optical observations
  83. GRB 250619B: Fermi GBM Final Real-time Localization
  84. Fermi trigger No 772058337: Global MASTER-Net observations report
  85. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  86. GRB 250615A: Kilonova-Catcher optical upper limits
  87. GRB 250619A: Fermi GBM Final Real-time Localization
  88. GRB 250617B: Assy AZT-20 Optical Observations
  89. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  90. Fermi GRB 250617A: Global MASTER-Net observations report
  91. GRB 250615A/EP250615a: FTW optical and NIR observations
  92. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  93. GRB 250617B: Swift/UVOT Detection
  94. GRB 250617B: Kilonova-Catcher optical afterglow detection
  95. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  96. GRB 250617B: COLIBRÍ optical observations
  97. GRB 250617B: NOT NIR observations of the afterglow
  98. GRB 250617B: Swift-XRT refined Analysis
  99. GRB 250617B: SVOM/VT optical observation
  100. GRB 250617B: NUTTelA-TAO early time 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