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"

4746 results found.

  1. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  2. EP250311a/GRB 250311A: EP-WXT detection
  3. GRB 250311B: SVOM detection of a burst
  4. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  5. The EP-WXT trigger 01709132425 is not a real source
  6. EP250308a: 1.6m Mephisto optical upper limits
  7. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  8. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  9. GRB 250309B: Swift-XRT refined Analysis
  10. GRB 250309B / IceCube-250309A: GECAM-B observations
  11. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  12. GRB 250309B / AT2025dws: SAO RAS optical observations
  13. GRB 250309B / AT2025dws: Swift-UVOT detection
  14. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  15. Fermi GRB 250309B: Global MASTER-Net observations report
  16. Fermi GRB 250309A: Global MASTER-Net observations report
  17. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  18. IceCube-250309A: No candidates from the Zwicky Transient Facility
  19. Fermi-LAT gamma-ray observations of IceCube-250309A
  20. GRB 250308A: SVOM/GRM observation of a bright short burst
  21. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  22. IceCube Alert 250309.32: Global MASTER-Net observations report
  23. EP250308a: Global MASTER-Net observations report
  24. EP250308a: FTW optical and NIR upper limits
  25. EP250308a: Einstein Probe detection of an X-ray transient
  26. GRB 250309A: Fermi GBM Final Real-time Localization
  27. GRB 250306A: EIRSAT-1 GMOD detection
  28. The EP-WXT trigger 01709132387 is likely a flaring star
  29. Fermi GRB 250307A: Global MASTER-Net observations report
  30. GRB 250306A: NuSTAR detection of the prompt emission
  31. GRB 250305A: AstroSat CZTI detection
  32. EP250302a:Xinglong optical observations
  33. GRB 250306A: AstroSat CZTI detection
  34. Fermi trigger No 762963055: Global MASTER-Net observations report
  35. Swift GRB 250306A: Global MASTER-Net observations report
  36. GRB 250305A: SVOM/GRM observation of a burst
  37. The EP-WXT trigger 01709132323 is likely a flaring star
  38. EP250304A: Upper limits from Fermi-GBM Observations
  39. Fermi GRB 250305A: Global MASTER-Net observations report
  40. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  41. EP250302a: Optical Observations at CrAO and SAO RAS
  42. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  43. EP 250304A: Optical counterpart detection by LCO
  44. EP250302A: 1.3m DFOT optical afterglow detection
  45. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  46. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  47. EP250302a: Mondy Continued Optical Observations
  48. EP250304a: TRT optical counterpart detection
  49. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  50. EP250304a: Global MASTER-Net observations report
  51. EP250304a: Einstein Probe detection of an X-ray transient
  52. EP250302a : GIT optical follow-up
  53. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  54. EP250302a: NUTTelA-TAO Early Measurments
  55. EP250302a: REM NIR upper limits
  56. EP250302a: Mondy Observations and Optical Light Curve
  57. INTEGRAL: end of scientific operations
  58. EP250302a: OHP/T193 optical and spectroscopic observations
  59. EP250302a: Global MASTER-Net observations report
  60. EP250302a: Xinglong F60B optical observation
  61. EP250302a: Einstein Probe detection of an X-ray transient
  62. EP250302a: SVOM/C-GFT optical observations
  63. EP250302a: Montarrenti Observatory optical detection
  64. Fermi GRB 250302A: Global MASTER-Net observations report
  65. EP250302a: FTW optical and NIR detection
  66. EP250302a: Nanshan/HMT optical counterpart detection
  67. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  68. The EP-WXT trigger 01709132140 is likely a flaring star
  69. Fermi trigger No 762205158: Global MASTER-Net observations report
  70. Fermi GRB 250225A: Global MASTER-Net observations report
  71. GRB 250225B: Swift detection of a burst
  72. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  73. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  74. GRB 250202B: VZLUSAT-2 detection
  75. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  76. Konus-Wind detection of GRB 250221A
  77. GRB 250221A: REM optical/NIR afterglow detection
  78. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  79. GRB 250221A: Swift detection of a burst with an optical counterpart
  80. Swift GRB250221.15: Global MASTER-Net OT detection
  81. Swift GRB250221.15: Global MASTER-Net observations report
  82. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  83. Fermi GRB 250217A: Global MASTER-Net observations report
  84. EP250215a: Global MASTER-Net observations report
  85. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  86. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  87. EP250207b: NOT optical counterpart candidate
  88. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  89. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  90. GRB 250207A: Skynet optical afterglow observations
  91. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  93. IceCube Alert 250207.09: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  95. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  96. GRB 250208A: Fermi GBM Final Real-time Localization
  97. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  99. GRB 250207B: MAXI/GSC detection
  100. GRB 250207A: Fermi GBM Final Real-time Localization

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