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"
  1. GRB 200306B: Fermi GBM Final Localization Correction
  2. GRB 200306C: OSN 1.5m afterglow detection
  3. GRB 200306C: Liverpool Telescope observations
  4. GRB 200306C: SAO RAS observations of OT
  5. GRB 200306C: GOTO upper limits
  6. GRB 200306A: Swift-XRT refined Analysis
  7. LIGO/Virgo S200302c: No notable candidates in GOTO imaging
  8. GRB 200306C: BOOTES-1 detection of the optical afterglow
  9. GRB 200306C: FRAM-ORM afterglow detection
  10. Swift GRB200306.95: Global MASTER-Net observations report
  11. GRB 200306C: Swift detection of a burst with an optical counterpart
  12. Swift GRB200306.95: Global MASTER-Net OT detection
  13. Swift GRB200306.95: Global MASTER-Net OT detection
  14. GRB 200306B: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo S200302c : No significant candidates in FRAM - TAROT - GRANDMA observations.
  16. GRB 200306A: Potential LCO Optical Afterglow Detection
  17. GRB 200306A: Swift detection of a burst
  18. Swift GRB200306.01: Global MASTER-Net observations report
  19. GRB 200228B: continued optical observations
  20. LIGO/Virgo S200225q: No notable candidates in GOTO imaging
  21. Konus-Wind observation of GRB200303A
  22. LIGO/Virgo S200302c: AstroSat CZTI upper limits
  23. GRB 200303A: Fermi GBM observation
  24. GRB200210A AstroSat observations
  25. GRB 200303A: Swift-XRT refined Analysis
  26. GRB 200303A: Swift-BAT refined analysis
  27. LIGO/Virgo S200302c: Upper limits from Insight-HXMT/HE observations
  28. GRB 200303A: NOT optical observations
  29. GRB 200303A: Swift/UVOT Upper Limits
  30. GRB 200303A: FRAM-ORM optical limit
  31. LIGO/Virgo S200303ba: Retraction of GW compact binary merger candidate
  32. GRB 200219A: AstroSat CZTI detection
  33. GRB 200303A: GOTO observations upper limit
  34. GRB 200303A: Optical limit from CAHA
  35. GRB 200228A: AstroSat CZTI detection
  36. GRB 200303A: CALET Gamma-Ray Burst Monitor detection
  37. GRB 200303A: Enhanced Swift-XRT position
  38. LIGO/Virgo S200302c: No transient candidates in CALET observations
  39. GRB 200219C: VLA Detection
  40. GRB 200303A: Swift detection of a burst
  41. Swift GRB200303.11: Global MASTER-Net observations report
  42. Fermi trigger No 604895668: Global MASTER-Net observations report
  43. GRB 200303A: Fermi GBM Final Real-time Localization
  44. LIGO/Virgo S200224ca: No counterpart candidates in TOROS observations
  45. LIGO/Virgo S200302c: Updated Sky Localization
  46. LIGO/Virgo S200302c: No significant counterpart candidates in Fermi-LAT observations
  47. LIGO/Virgo S200302c: No counterpart candidates in KAIT observations
  48. LIGO/Virgo S200302c: no counterpart candidates in the Swift/BAT observations
  49. LIGO/Virgo S200224ca: Transient found in Swift/UVOT counterpart search
  50. LIGO/Virgo S200302c: No counterpart candidates in HAWC observations
  51. LIGO/Virgo S200302c: Upper limits from Fermi-GBM Observations
  52. LIGO/Virgo S200302c: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  53. LIGO/Virgo S200302c : no neutrino counterpart candidate in ANTARES search
  54. LIGO/Virgo S200302c: upper limits from AGILE/MCAL observations
  55. LIGO/Virgo S200225q: AstroSat CZTI upper limits
  56. LIGO/Virgo S200219ac: AstroSat CZTI upper limits
  57. LIGO/Virgo S200302c: Coverage and upper limits from MAXI/GSC observations
  58. LIGO/Virgo S200302c: Upper limits from IceCube neutrino searches
  59. LIGO/Virgo S200302c: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo S200302c: Global MASTER-Net observations report
  61. GRB 200228B: Mondy, TSHAO, AbAO and CrAO optical observations, afterglow candidate
  62. LIGO/Virgo S200225q : No significant candidates in TAROT - FRAM - GRANDMA observations.
  63. GRB 200228B: LCO Optical Upper Limit
  64. GRB 200228B: Swift-BAT refined analysis
  65. GRB 200228B: RATIR Optical Observations
  66. GRB 200228B: Liverpool Telescope imaging
  67. GRB 200228B: Swift-XRT refined Analysis
  68. Swift GRB 200228B: Global MASTER-Net observations report
  69. GRB 200228B: Swift/UVOT Upper Limits
  70. GRB 200228B: RATIR Optical Observations
  71. GRB 200228B: Fermi GBM observation
  72. GRB 200227A: RATIR Optical Observations
  73. IceCube-200227A: Upper limits from a search for additional neutrino events in IceCube
  74. GRB 200228B: KAIT Optical Upper Limit
  75. LIGO/Virgo S200224ca: Updated Sky Localization and EM Bright Classification
  76. GRB 200228C: Insight-HXMT/HE detection
  77. GRB 200228A: Fermi GBM observation
  78. GRB 200228A: Swift/BAT detection and arcminute localization from GUANO
  79. LIGO/Virgo S200213t: No significant EM counterparts identified from continued GECKO observation of host galaxy candidates
  80. GRB 200227A: Mondy optical upper limit
  81. GRB 200228B: Enhanced Swift-XRT position
  82. Fermi-LAT Gamma-ray Observations of IceCube-200227A
  83. GRB 200228B: Swift detection of a burst
  84. GRB 200228B: Fermi GBM Final Real-time Localization
  85. Fermi trigger No 604565918: Global MASTER-Net observations report
  86. GRB 200227A: Insight-HXMT/HE detection
  87. IceCube-200227A : Upper limits from Insight-HXMT/HE observations
  88. GRB 200227A: Swift-XRT refined Analysis
  89. GRB 200228A: BALROG localization (Fermi Trigger 604565918 / GRB 200228291)
  90. GRB 200228A: Fermi GBM Final Real-time Localization
  91. GRB 200227A: Swift-BAT refined analysis
  92. GRB 200219A: ATCA 5/9 GHz radio observations
  93. GRB 200227A: Swift/UVOT Upper Limits
  94. GRB 200227A: Enhanced Swift-XRT position
  95. HAWC-200216A: No Neutrino Counterpart in ANTARES Search
  96. IceCube-200227A: Upper limits from Fermi-GBM Observations
  97. GRB 200224A: Mondy optical upper limit
  98. GRB 200227A: Fermi GBM observation
  99. LIGO/Virgo S200224ca : No significant candidates in TAROT - FRAM - GRANDMA observations
  100. IceCube-200227A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation

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