Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

16161 results found.

  1. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  2. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  3. GRB 250207A: FRAM-Auger optical detection
  4. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  5. GRB 250207A: REM optical afterglow detection
  6. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  7. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  8. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  9. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  10. GRB 250129A: Continued AbAO and Mondy optical observations
  11. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  12. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  13. GRB 250207A: Swift detection of a burst with optical counterpart
  14. GRB 250205A: REM NIR upper limit
  15. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  16. GRB 250127C: SVOM/GRM observation of a burst
  17. GRB 250204B: SVOM/GRM observation of a likely short burst
  18. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  19. GRB 250205A: Swift/XRT detection
  20. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  21. GRB250205A: SVOM/VT optical afterglow detection
  22. GRB 250205A: GOTO optical upper limits
  23. GRB 250205A: OHP/T193 optical counterpart candidate
  24. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  25. GRB 250205A: SVOM detection of a burst
  26. GRB 250129A: LCO late afterglow detection
  27. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  28. GRB 250129a: Liverpool Telescope optical follow-up
  29. GRB 240129A: further SAO RAS optical observations
  30. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  31. GRB 250129A: SVOM/C-GFT optical observations
  32. Swift GRB250129A: MASTER 4 days observations report
  33. GRB 250129A: 1.3m DFOT Optical observations
  34. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  35. GRB 250129A: Skynet Continued Optical Observations
  36. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  37. GRB 250129A: SAO RAS optical observations
  38. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  39. GRB 250129A: optical photometry from Konkoly
  40. GRB 250129A: COLIBRÍ Optical Observations
  41. GRB 250128B: VLA possible radio detection
  42. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  43. GRB 250129A: iTelescope optical observation
  44. GRB 250129A: NOT optical observations of continuining activity
  45. GRB 250129a: Liverpool Telescope optical follow-up
  46. GRB 250129A: AKO Optical Afterglow Detection
  47. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  48. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  49. Ep250125A: 1.3m DFOT optical upper limit
  50. GRB 250129A: Skynet optical observations
  51. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  52. GRB 250128B: Gemini-North optical extended source detection
  53. GRB 250128B: TNG optical upper limit
  54. GRB 250129A: Swift/UVOT Detection
  55. GRB 250127A: CrAO and Terskol optical upper limits
  56. GRB 250128B: NOT optical upper limit
  57. GRB 250128B: VLT/FORS2 optical observations
  58. GRB 250129A: REM optical/NIR afterglow detection
  59. GRB 250129A: OHP/T193 optical and spectroscopy observations
  60. GRB 250129A: Early afterglow detection by LCO.
  61. GRB 250128B: OHP/T193 optical upper limit
  62. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  63. GRB 250129A: LCO optical observations
  64. GRB 250129A: NOT optical observations and redshift confirmation
  65. GRB 250129A: GOTO optical observations show brightening afterglow
  66. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  67. GRB 250129A: Swift detection of a burst with an optical counterpart
  68. Swift GRB 250129A: Global MASTER-Net OT detection
  69. GRB 250128B: GOTO optical upper limit
  70. GRB 250128B: LCO optical observations
  71. GRB 250127A: LCO optical upper limit
  72. EP250125a: Optical upper limit with Kinder observations
  73. EP250125a: REM optical counterpart detection
  74. EP250125a: Swift/XRT detection of a fading counterpart
  75. EP250125a: a new X-ray transient detected by Einstein Probe
  76. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  77. EP250108a: AbAO, CMO and Terskol optical upper limits
  78. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  79. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  80. EP 250108A: Late-time optical observation by LCO
  81. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  82. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  83. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  84. EP250108a / AT2025kg: GMG Optical Observations
  85. EP250108a / AT2025kg: VLA radio upper limit
  86. GRB 241217A / EP241217B: radio detection with the VLA
  87. GRB 250114B: Swift-XRT afterglow detection
  88. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  89. GRB 250114B: Liverpool Telescope optical upper limit
  90. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  91. GRB 250114A: LCO optical counterpart detection.
  92. GRB 250114B: OHP/T193 optical upper limit
  93. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  94. GRB 250114A: LCOGT optical afterglow i-band detection
  95. GRB 250114B : GIT optical upper limit
  96. EP250111a: SAO RAS optical upper limit
  97. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  98. GRB 250114A: REM detection of the optical and NIR counterpart
  99. Swift GRB250114A: Global MASTER-Net OT detection
  100. GRB 250114A: LCO optical observations

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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