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## FERMILTRNS - Fermi LAT Long-Term Transient Source Catalog |
HEASARC Archive |

Baldini et al. (2021), "Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data", <ApJS, 256, 13B (2021)> =2021ApJS..256...13B

**Source_Number**

Unique, sequential identification number per source in catalog. This is the
same for multiple flares of the same source.

**Name**

The IAU-style J2000 position-based source designation, e.g., '1FLT JHHMM+DDMM'.

**RA**

The Right Ascension of the source in the selected equinox. This was given in
J2000 decimal degree coordinates to an accuracy of 10^{-3} degrees (3.6
arcseconds) in the original reference.

**Dec**

The Declination of the source in the selected equinox. This was given in
J2000 decimal degree coordinates to an accuracy of 10^{-3} degrees (3.6
arcseconds) in the original reference.

**LII**

The Galactic longitude of the source.

**BII**

The Galactic latitude of the source.

**Semi_Major_Axis**

The semi-major axis of the error ellipse at 95% confidence, in arcminutes.

**Semi_Minor_Axis**

The semi-minor axis of the error ellipse at 95% confidence, in arcminutes.

**Position_Angle**

The position angle of the error ellipse at 95% confidence and defined as
degrees east of north.

**Likelihood**

The likelihood test statistic based on maximum likelihood analysis and
defined as 2*Delta(log L), where L is the likelihood function, for the 100
MeV - 300 GeV analysis. This test statistic quantifies how significantly a
source emerges from the background by comparing L with and without a source
(see Section 2 of the reference paper).

**Time_Bin**

The time bin in which the source was detected with the largest likelihood
test statistic. These time bins correspond to one month (2630000 seconds)
that split the total data coverage between 2008 August 4 15:43:36 UTC to 2018
August 5 10:23:32 UTC, e.g., 0-119 stand for the first 120 months starting
August 4, 2008, 0.5-119.5 stands for 120 15-day shifted months starting
August 19, 2008.

**Num_Flares**

The number of flares for this source.

**Pred_Number**

The number of predicted events in the model, which aims to calculate a false
positive rate by simulating 120 month-long data sets including Galactic and
extragalactic diffuse emission with statistical fluctuations of the
background.

**PLaw_Photon_Index**

The photon index, Gamma, for the power law fit of the spectrum, defined as
dN/dE = K * (E/1 GeV)^{-Gamma}, where K gives the scale flux normalization.

**PLaw_Photon_Index_Error**

The 1-sigma uncertainty in the photon index for the power law fit of the
spectrum.

**Photon_Flux**

The photon flux, in units of photons/cm^{2}/s, determined from the fit to the
power law spectrum. In the original catalog data file, these values had five
significant digits in the mantissa. With the authors' approval, the HEASARC
displays only two significant digits as appropriate to the number of
significant digits in the associated uncertainty.

**Photon_Flux_Error**

The 1-sigma uncertainty in the photon flux, in photons/cm^{2}/s. In the
original catalog data file, these values had five significant digits in the
mantissa. With the authors' approval, the HEASARC displays only two
significant digits.

**Flux**

The energy flux, in erg/s/cm^{2}, for the 100-MeV to 300-GeV range obtained by
spectral fitting in this energy range. In the original catalog data file,
these values had five significant digits in the mantissa. With the authors'
approval, the HEASARC displays only two significant digits as appropriate to
the number of significant digits in the associated uncertainty. The HEASARC
also converted these values from MeV/s/cm^{2} to erg/s/cm^{2}.

**Flux_Error**

The 1-sigma uncertainty in the 100-MeV to 300-GeV energy flux, in
erg/cm^{2}/s. In the original catalog data file, these values had five
significant digits in the mantissa. With the authors' approval, the HEASARC
displays only two significant digits. The HEASARC also converted these values
from MeV/s/cm^{2} to erg/s/cm^{2}.

**Fermi_Name**

The source name associated with the general Fermi-LAT xFGL (e.g.,
4FGL-DR2) or FL8Y catalogs.

**Gamma_Name**

The source name associated with other gamma-ray source catalogs (see Section
3.2 of reference paper for details).

**Fava_Name**

The source name associated with 2FAV source catalog (Abdollahi et al, 2017).

**LMC_Flag**

Flag 'Y' indicates that the source is located in the Large Magellanic Cloud
(LMC) region. Otherwise, the value is 'N'.

**Cena_Flag**

Flag 'Y' Indicates that the source is located near Cen A. Otherwise, the
value is 'N'.

**Source_Type**

The class designation of the associated source, which is described in Section
3.1 of the reference paper, and marked to represent the following:

fsrq = Flat spectrum Radio Quasar bll = BL Lacertae object css = Compact Steep Spectrum radio source ssrq = Steep Spectrum Radio Quasar rg = Radio Galaxy bcu = Blazars of Uncertain Type agn = Active Galactic Nuclei of other type unass = unassociated

**Assoc_Name**

The designation of the most likely associated counterpart.

**Assoc_Prob_Bay**

Probability of association from the Bayesian method.

**Assoc_RA**

The Right Ascension of the associated source.

**Assoc_Dec**

The Declination of the associated source.

**Assoc_Redshift**

The redshift of the associated source.

**Flux_1420_MHz**

The radio flux density, in mJy, for the source.

**Log_Freq_Peak**

The logarithm (base 10) of the synchrotron peak frequency, in Hz, measured
with a third degree polynomial fit function to the broadband SED (following
Ackermann et al. 2015, see Section 4.2 of reference paper).

**Low_Confidence_Flag**

Flag 'Y' indicates that the source has low confidence, due to test statistic
(likelihood parameter) value < 30 and only one monthly detection.

**Class**

The HEASARC Browse object classification, based on the source_type parameter.