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"

20561 results found.

  1. GRB 251003A: J-band detection with WINTER
  2. GRB 251002A: NIR observations with WINTER
  3. Fermi GBM Sub-Threshold Detection of GRB 250910A
  4. GRB 251001B: NIR observations with WINTER
  5. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  6. GRB 251003A: Swift/UVOT Upper Limits
  7. GRB 251002A: Swift/UVOT detection
  8. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  9. GRB 251003A: COLIBRÍ photometric redshift
  10. GRB 251003A: GOTO detection of the optical counterpart
  11. GRB 251002A: GOTO detection of optical counterpart
  12. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  13. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  14. GRB 251003A: Kilonova-Catcher optical afterglow detection
  15. GRB 251002A: Swift-XRT afterglow detection
  16. GRB 251001B: AbAO optical upper limit
  17. GRB 251002A: Kilonova-Catcher optical afterglow detection
  18. GRB 251002A: AbAO optical observations
  19. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  20. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  21. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  22. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  23. GRB 251003A: LCOGT Optical Detection
  24. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  25. GRB 251003A: 1.5m OSN afterglow candidate
  26. Swift GRB251003A: Global MASTER-Net observations report
  27. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  28. GRB 251002A: SAO RAS optical observations
  29. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  30. GRB 251002A: LCO optical observation
  31. Fermi GRB 251002A: Global MASTER-Net observations report
  32. GRB 251001B: Swift/UVOT Detection
  33. GRB 251001B: COLIBRÍ optical observations
  34. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  35. GRB 251001B: NOT optical observations
  36. Swift GRB 251001B: Global MASTER-Net observations report
  37. GRB 251001B: Further GOTO observations of optical counterpart.
  38. GRB 251001B: LCOGT Optical Observations
  39. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  40. GRB 251001B: GOTO optical counterpart detection
  41. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  42. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  43. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  44. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  45. GRB 250925A: MAO/AZT-22 optical observations
  46. Fermi GRB 250929A: Global MASTER-Net observations report
  47. GRB 250925A: Mondy I-band optical observations
  48. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  49. Fermi trigger No 780609036: Global MASTER-Net observations report
  50. IceCube Alert 250926.52: Global MASTER-Net observations report
  51. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  52. GRB 250925A: Swift/UVOT Upper Limits
  53. GRB 250925A: Mondy and AbAO optical observations
  54. GRB 250925A: COLIBRÍ photometric redshift
  55. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  56. GRB 250925A: JinShan optical observations
  57. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  58. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  59. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  60. Fermi GRB 250926A: Global MASTER-Net observations report
  61. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  62. GRB250925A: Liverpool Telescope optical observations
  63. GRB 250925A: NOT optical afterglow candidate
  64. GRB 250925A: Leavitt Observatory optical upper limit
  65. Swift GRB 250925A: Global MASTER-Net observations report
  66. GRB 250924A: 1.6m Mephisto optical upper limits
  67. GRB 250924A: SAO RAS optical observations
  68. GRB 250924A: NOT optical observations
  69. GRB 250924A: Swift/UVOT Detection
  70. GRB 250924A: J-band detection with WINTER
  71. GRB 250924A: GROWTH-India Telescope Upper Limits
  72. GRB 250924A: KAIT optical observations
  73. GRB 250924A: Mondy optical observations, afterglow fading
  74. GRB 250924A: Kilonova-Catcher optical afterglow detection
  75. GRB 250920C: Kilonova-Catcher optical afterglow detection
  76. GRB 250920C: TRT optical observation
  77. GRB 250924A: COLIBRÍ optical observations
  78. Swift GRB 250924A: Global MASTER-Net observations report
  79. GRB 250919A / EP250919a: further LCO optical observation
  80. GRB 250924A: DDOTI Detection of the Optical Counterpart
  81. GRB 250920C: KAIT optical observations
  82. GRB 250920C: VLT redshift confirmation z = 1.399
  83. EP250911a: e-MERLIN radio observations
  84. GRB 250920B: CrAO ZTSH optical observations
  85. GRB 250920C: SALT redshift confirmation
  86. GRB 250920C: COLIBRÍ optical observations
  87. Fermi GRB 250922B: Global MASTER-Net observations report
  88. GRB 250920B: SAO RAS optical observations
  89. GRB 250920C: NIR observations with WINTER
  90. GRB 250920B: NIR observations with WINTER
  91. Fermi trigger No 780156732: Global MASTER-Net observations report
  92. GRB 250920C: PRIME near-infrared detection
  93. GRB 250916A: Swift/UVOT Detection
  94. GRB 250916A: CrAO ZTSh R-band optical observations
  95. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  96. GRB 250920B: Asiago optical observations
  97. GRB 250920B: Kitab-ISON optical upper limit
  98. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  99. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  100. GRB 250920C: GROWTH-India Telescope 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