Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

24911 results found.

  1. GRB 250702F: Leavitt Observatory optical observations
  2. GRB 250702F: AKO Optical Afterglow Detection
  3. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  4. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  5. GRB 250702F: Skynet Optical Observations
  6. GRB 250424A: VIRT Optical Upper Limit
  7. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  8. GRB 250702F: TRT Optical Observation
  9. GRB 250703A: DDOTI Optical Upper Limit
  10. GRB 250702F: REM optical afterglow detection
  11. EP250702a: Global MASTER-Net observations report
  12. GRB 250702F: DDOTI Optical Observation
  13. GRB 250702F: COLIBRÍ Observations of the Afterglow
  14. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  15. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  16. GRB 250702F: Enhanced Swift-XRT position
  17. GRB 250702F: NOT observations of the optical afterglow
  18. GRB 250702F: Swift detection of a burst with an optical counterpart
  19. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  20. GRB 250702A: Fermi GBM Detection
  21. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  22. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  23. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  24. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  25. GRB 250628B: Swift-XRT observations
  26. GRB 250628B: EP-FXT counterpart detection
  27. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  28. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  29. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  30. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  31. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  32. GRB 250628A: REM optical/NIR upper limits
  33. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  34. GRB 250628B: SVOM detection of a long burst
  35. GRB 250628A: VLT/X-shooter upper limits
  36. GRB 250628A: Swift/UVOT Upper Limits
  37. GRB 250628A: Swift-XRT refined Analysis
  38. GRB 250628A: Enhanced Swift-XRT position
  39. GRB 250628A: Swift detection of a burst
  40. GRB 250625A: Swift-BAT refined analysis
  41. GRB 250625A: Leavitt Observatory afterglow detection
  42. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  43. GRB 250625A: SVOM/C-GFT upper limit in early phase
  44. GRB 250625A: Swift/UVOT Upper Limits
  45. GRB 250625A: ABObservatory afterglow detection
  46. GRB 250625A: OHP/T193 optical detection
  47. GRB 250625A: COLIBRÍ optical observations
  48. GRB 250625A: Swift-XRT refined Analysis
  49. GRB 250625A: JinShan optical observations
  50. GRB250625A: Fermi GBM Observation
  51. GRB 250620B: Fermi GBM Observation
  52. GRB 250625A: SAO RAS possible optical afterglow
  53. GRB 250625A: Enhanced Swift-XRT position
  54. GRB 250625A: Swift detection of a burst
  55. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  56. GRB 241018A: Maidanak optical observations
  57. GRB 250620C: AstroSat CZTI detection
  58. Fermi GRB 250624A: Global MASTER-Net observations report
  59. GRB 250521A: VZLUSAT-2 detection
  60. GRB 250617B: Swift-BAT refined analysis
  61. Fermi trigger No 772190032: Global MASTER-Net observations report
  62. IPN triangulation of GRB 250620С (long/bright)
  63. GRB 250620C: SVOM/GRM observation
  64. GRB 250620A: SVOM/GRM observation of a short burst
  65. GRB250620A: Fermi GBM Observation
  66. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  67. GRB 250619B: Fermi GBM Observation
  68. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  69. GRB250620C: Fermi GBM Observation
  70. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  71. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  72. Fermi trigger No 772128434: Global MASTER-Net observations report
  73. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  74. GRB 250617B: Nickel telescope optical observations
  75. GRB 250615A: Kilonova-Catcher optical upper limits
  76. GRB 250617B: Assy AZT-20 Optical Observations
  77. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  78. Fermi GRB 250617A: Global MASTER-Net observations report
  79. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  80. GRB 250617B: Swift/UVOT Detection
  81. GRB 250617B: Kilonova-Catcher optical afterglow detection
  82. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  83. GRB 250617B: COLIBRÍ optical observations
  84. GRB 250617B: NOT NIR observations of the afterglow
  85. GRB 250617B: Swift-XRT refined Analysis
  86. GRB 250617B: NUTTelA-TAO early time optical observations
  87. GRB 250617B: Enhanced Swift-XRT position
  88. GRB 250617B: Fermi GBM Observation
  89. GRB 250615A: Swift-BAT refined analysis
  90. GRB 250617B: SAO RAS optical observations
  91. GRB 250617B: Swift detection of a burst with an optical counterpart
  92. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  93. EP#01709178975: Swift-XRT counterpart detection
  94. EP-WXT trigger 01709178975: GOTO optical upper limit
  95. GRB 250615A / EP250615a: AstroSat CZTI detection
  96. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  97. GRB 250615A: COLIBRÍ optical upper limit
  98. GRB 250615A: DDOTI Optical Upper Limit
  99. GRB 250615A: Swift/UVOT Upper Limits
  100. GRB 250615A: Swift-XRT refined Analysis

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