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"

15716 results found.

  1. GRB 250506A: Xinglong 2.16m optical upper limit
  2. GRB 250506A: REM optical/NIR upper limits
  3. GRB 250506A: Swift XRT observations and possible counterpart detection
  4. GRB 250506A: TRT optical observations
  5. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  6. GRB 250504A: VLT/X-shooter upper limits
  7. GRB 250504A: SVOM/VT upper limit
  8. GRB 250504A: REM optical/NIR observations
  9. GRB 250502A: REM optical/NIR observations
  10. GRB 250504A: MeerLICHT optical afterglow detection
  11. GRB 250502A: Mondy and Tien-Shan Optical Observations
  12. GRB 250502A: KAIT optical observations
  13. GRB 250502A: Montarrenti Observatory optical detection
  14. GRB 250502A: Swift-XRT afterglow detection
  15. GRB 250502A: NOT optical observations
  16. GRB 250502a: Liverpool Telescope optical follow-up
  17. GRB 250502A: AKO Optical Afterglow Detection
  18. GRB 250502A: LCO optical counterpart detection
  19. GRB 250502B: DDOTI Optical Observations
  20. GRB 250502A: Early optical counterpart detection by LCO.
  21. GRB 250430A: Swift/UVOT Detection
  22. GRB 250502A: SVOM/VT optical bump
  23. GRB 250502A: TRT optical afterglow confirmation
  24. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  25. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  26. GRB 250502A: SVOM detection of a burst
  27. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  28. GRB 250430A: SVOM/VT optical observations
  29. GRB 250430A: KAIT optical observations
  30. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  31. GRB 250430A / EP250430a: J-band upper limits with WINTER
  32. GRB 250430A: NUTTelA-TAO Early Measurements
  33. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  34. GRB 250430A: DDOTI Optical Observations
  35. GRB 250430A: Leavitt Observatory optical upper limit
  36. GRB 250430A: Bassano Bresciano Observatory upper limit
  37. GRB 250430A : MITSuME Akeno optical upper limits
  38. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  39. GRB 250430A: AKO Optical Afterglow Detection
  40. GRB 250430A: Kanata optical upper limit
  41. EP 250427A: Optical counterpart detection by LCO.
  42. GRB 250430A: Swift detection of a burst with optical counterpart
  43. EP250428b: FTW optical and NIR observations
  44. EP250427a/GRB250427A: HCT optical follow-up
  45. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  46. SVOM/sb25043004: SVOM detection of a X-ray transient
  47. EP250428b: GROWTH-India telescope optical upper limit
  48. EP250428b: SAO RAS optical upper limit
  49. EP250428b: LAST optical upper limit
  50. GRB 250427A: Swift/UVOT Detection
  51. EP250427a / GRB 250427A: OHP/T193 photometric observations
  52. EP250427a: EP-FXT follow-up observations
  53. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  54. EP250427a: Lesedi optical counterpart detection
  55. EP250427A: COLIBRÍ Continuing Optical Observations
  56. GRB250427A/EP250427a GIT optical afterglow detection:
  57. EP250427a: LT optical counterpart detection
  58. GRB 250427A: Swift-XRT refined Analysis
  59. EP250427a / GRB 250427A: LCO optical counterpart detection
  60. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  61. EP250427A/GRB250427A: Keck/LRIS redshift
  62. EP250427a: REM optical/NIR afterglow detection
  63. GRB 250424A: LCO optical observation
  64. EP250427A: COLIBRÍ Optical Detection
  65. EP250427a: TRT optical counterpart detection
  66. EP 250427a: BOOTES-7 optical afterglow candidate
  67. GRB 250424A: SVOM/GRM observation of a long burst
  68. GRB 250424A: PRIME near-infrared detection
  69. GRB 250424A: WINTER J-band detection
  70. GRB 250424A: SVOM/VT optical observation
  71. GRB 250419A: Mondy Optical Observations
  72. GRB 250424A: Swift/UVOT Detection
  73. Fermi-LAT gamma-ray observations of IceCube-250421A
  74. GRB 250424A: Skynet Optical Observations
  75. GRB 250424A: Kilonova-Catcher optical afterglow detection
  76. GRB 250419a: Continued Liverpool Telescope observations
  77. GRB 250419A: Liverpool Telescope optical upper limit
  78. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  79. GRB 250424A: BlackGEM optical afterglow detection
  80. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  81. GRB 250424A: likely host galaxy
  82. GRB 250424A: DDOTI Afterglow Detection
  83. GRB 250424A: REM optical/NIR afterglow detection
  84. GRB 250424A: Swift detection of a burst with an optical counterpart
  85. Swift GRB 250424A: Global MASTER-Net OT detection
  86. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  87. EP250421a: Nickel optical upper limit
  88. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  89. SVOM/sb25042207: BOOTES-2 early optical upper limit
  90. SVOM/sb25042207: GOTO optical upper limits
  91. GRB250419A: VLA radio detection
  92. GRB 250419A: Mephisto Multi-band Optical Detection
  93. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  94. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  95. EP250421a: NOT optical observations
  96. GRB 250419A: Optical Observations via Virtual Telescope Project
  97. EP250421a: REM optical upper limit
  98. EP250421a: Swift/XRT counterpart detection
  99. EP250421A: COLIBRÍ Optical Upper Limit
  100. GRB 250419A: Mondy Continued 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