Skip to main content
New! BOOM Notices and Schema v7.0.0. 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"

20489 results found.

  1. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  2. GRB 251003A: Swift/UVOT Upper Limits
  3. GRB 251002A: Swift/UVOT detection
  4. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  5. GRB 251003A: COLIBRÍ photometric redshift
  6. GRB 251003A: GOTO detection of the optical counterpart
  7. GRB 251002A: GOTO detection of optical counterpart
  8. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  9. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  10. GRB 251003A: Kilonova-Catcher optical afterglow detection
  11. GRB 251002A: Swift-XRT afterglow detection
  12. GRB 251001B: AbAO optical upper limit
  13. GRB 251002A: Kilonova-Catcher optical afterglow detection
  14. GRB 251002A: AbAO optical observations
  15. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  16. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  17. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  18. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  19. GRB 251003A: LCOGT Optical Detection
  20. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  21. GRB 251003A: 1.5m OSN afterglow candidate
  22. Swift GRB251003A: Global MASTER-Net observations report
  23. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  24. GRB 251002A: SAO RAS optical observations
  25. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  26. GRB 251002A: LCO optical observation
  27. Fermi GRB 251002A: Global MASTER-Net observations report
  28. GRB 251001B: Swift/UVOT Detection
  29. GRB 251001B: COLIBRÍ optical observations
  30. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  31. GRB 251001B: NOT optical observations
  32. Swift GRB 251001B: Global MASTER-Net observations report
  33. GRB 251001B: Further GOTO observations of optical counterpart.
  34. GRB 251001B: LCOGT Optical Observations
  35. GRB 251001B: GOTO optical counterpart detection
  36. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  37. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  38. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  39. GRB 250925A: MAO/AZT-22 optical observations
  40. Fermi GRB 250929A: Global MASTER-Net observations report
  41. GRB 250925A: Mondy I-band optical observations
  42. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  43. Fermi trigger No 780609036: Global MASTER-Net observations report
  44. IceCube Alert 250926.52: Global MASTER-Net observations report
  45. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  46. GRB 250925A: Swift/UVOT Upper Limits
  47. GRB 250925A: Mondy and AbAO optical observations
  48. GRB 250925A: COLIBRÍ photometric redshift
  49. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  50. GRB 250925A: JinShan optical observations
  51. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  52. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  53. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  54. Fermi GRB 250926A: Global MASTER-Net observations report
  55. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  56. GRB250925A: Liverpool Telescope optical observations
  57. GRB 250925A: NOT optical afterglow candidate
  58. GRB 250925A: Leavitt Observatory optical upper limit
  59. Swift GRB 250925A: Global MASTER-Net observations report
  60. GRB 250924A: 1.6m Mephisto optical upper limits
  61. GRB 250924A: SAO RAS optical observations
  62. GRB 250924A: NOT optical observations
  63. GRB 250924A: Swift/UVOT Detection
  64. GRB 250924A: J-band detection with WINTER
  65. GRB 250924A: GROWTH-India Telescope Upper Limits
  66. GRB 250924A: KAIT optical observations
  67. GRB 250924A: Mondy optical observations, afterglow fading
  68. GRB 250924A: Kilonova-Catcher optical afterglow detection
  69. GRB 250920C: Kilonova-Catcher optical afterglow detection
  70. GRB 250920C: TRT optical observation
  71. GRB 250924A: COLIBRÍ optical observations
  72. Swift GRB 250924A: Global MASTER-Net observations report
  73. GRB 250919A / EP250919a: further LCO optical observation
  74. GRB 250924A: DDOTI Detection of the Optical Counterpart
  75. GRB 250920C: KAIT optical observations
  76. EP250911a: e-MERLIN radio observations
  77. GRB 250920B: CrAO ZTSH optical observations
  78. GRB 250920C: SALT redshift confirmation
  79. GRB 250920C: COLIBRÍ optical observations
  80. Fermi GRB 250922B: Global MASTER-Net observations report
  81. GRB 250920B: SAO RAS optical observations
  82. GRB 250920C: NIR observations with WINTER
  83. GRB 250920B: NIR observations with WINTER
  84. Fermi trigger No 780156732: Global MASTER-Net observations report
  85. GRB 250920C: PRIME near-infrared detection
  86. GRB 250916A: Swift/UVOT Detection
  87. GRB 250916A: CrAO ZTSh R-band optical observations
  88. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  89. GRB 250920B: Asiago optical observations
  90. GRB 250920B: Kitab-ISON optical upper limit
  91. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  92. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  93. GRB 250920C: GROWTH-India Telescope optical observations
  94. GRB 250916A: FTW optical and NIR observations of the counterpart
  95. GRB 250920C: Swift/UVOT Detection
  96. Swift GRB 250920C: Global MASTER-Net observations report
  97. GRB 250920B: Swift/UVOT Detection
  98. GRB 250920B: FTW optical and NIR observations of the counterpart
  99. GRB 250920C: Optical counterpart detection by LCO
  100. GRB 250920B: SVOM/C-GFT 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